qiuluoyuweiliang

SSM整合以及相关补充

我们在前面已经学习了Maven基本入门,Spring,SpringMVC,MyBatis三件套

现在我们来通过一些简单的案例,将我们最常用的开发三件套整合起来,进行一次完整的项目展示

温馨提示:在阅读本篇文章前,请学习Maven,Spring,SpringMVC,MyBatis等内容

SSM整合案例

接下来我们通过各个部分的准备与介绍进行一次SSM项目的内容整合

案例介绍阶段

案例介绍:

  • 我们希望通过网页进行操作数据库内容

数据库目前资料:

案例准备阶段

  1. 创建工程

我们采用Maven项目的maven-webapp创建项目

  1. 补充相关文档以及设置文档构造名称

案例书写阶段

  1. 数据库准备阶段
CREATE DATABASE SMM;

USE SMM;

-- ----------------------------
-- Table structure for tbl_book
-- ----------------------------
DROP TABLE IF EXISTS `tbl_book`;
CREATE TABLE `tbl_book`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `type` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `description` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 13 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of tbl_book
-- ----------------------------
INSERT INTO `tbl_book` VALUES (1, '计算机理论', 'Spring实战 第5版', 'Spring入门经典教程,深入理解Spring原理技术内幕');
INSERT INTO `tbl_book` VALUES (2, '计算机理论', 'Spring 5核心原理与30个类手写实战', '十年沉淀之作,手写Spring精华思想');
INSERT INTO `tbl_book` VALUES (3, '计算机理论', 'Spring 5 设计模式', '深入Spring源码剖析Spring源码中蕴含的10大设计模式');
INSERT INTO `tbl_book` VALUES (4, '计算机理论', 'Spring MVC+MyBatis开发从入门到项目实战', '全方位解析面向Web应用的轻量级框架,带你成为Spring MVC开发高手');
INSERT INTO `tbl_book` VALUES (5, '计算机理论', '轻量级Java Web企业应用实战', '源码级剖析Spring框架,适合已掌握Java基础的读者');
INSERT INTO `tbl_book` VALUES (6, '计算机理论', 'Java核心技术 卷I 基础知识(原书第11版)', 'Core Java 第11版,Jolt大奖获奖作品,针对Java SE9、10、11全面更新');
INSERT INTO `tbl_book` VALUES (7, '计算机理论', '深入理解Java虚拟机', '5个维度全面剖析JVM,大厂面试知识点全覆盖');
INSERT INTO `tbl_book` VALUES (8, '计算机理论', 'Java编程思想(第4版)', 'Java学习必读经典,殿堂级著作!赢得了全球程序员的广泛赞誉');
INSERT INTO `tbl_book` VALUES (9, '计算机理论', '零基础学Java(全彩版)', '零基础自学编程的入门图书,由浅入深,详解Java语言的编程思想和核心技术');
INSERT INTO `tbl_book` VALUES (10, '市场营销', '直播就该这么做:主播高效沟通实战指南', '李子柒、李佳琦、薇娅成长为网红的秘密都在书中');
INSERT INTO `tbl_book` VALUES (11, '市场营销', '直播销讲实战一本通', '和秋叶一起学系列网络营销书籍');
INSERT INTO `tbl_book` VALUES (12, '市场营销', '直播带货:淘宝、天猫直播从新手到高手', '一本教你如何玩转直播的书,10堂课轻松实现带货月入3W+');
  1. 导入相关坐标
<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.itheima</groupId>
  <artifactId>springmvc_08_ssm</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <dependencies>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.2.10.RELEASE</version>
    </dependency>
	
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-jdbc</artifactId>
      <version>5.2.10.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-test</artifactId>
      <version>5.2.10.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.6</version>
    </dependency>

    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis-spring</artifactId>
      <version>1.3.0</version>
    </dependency>

    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.47</version>
    </dependency>

    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid</artifactId>
      <version>1.1.16</version>
    </dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>

    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.9.0</version>
    </dependency>
      
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.tomcat.maven</groupId>
        <artifactId>tomcat7-maven-plugin</artifactId>
        <version>2.1</version>
        <configuration>
          <port>80</port>
          <path>/</path>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>
  1. jdbc配置资文档准备
// jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/ssm
jdbc.username=root
jdbc.password=123456
  1. SpringConfig配置类
// SpringConfig

package com.itheima.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.PropertySource;
import org.springframework.transaction.annotation.EnableTransactionManagement;

// Spring配置类
@Configuration
// 扫描包
@ComponentScan({"com.itheima.service"})
// 资源载入
@PropertySource("classpath:jdbc.properties")
// 与MyBatis链接
@Import({JdbcConfig.class,MyBatisConfig.class})
// 开启事务平台
@EnableTransactionManagement
public class SpringConfig {
}
  1. MyBatisConfig配置类
// JdbcConfig

package com.itheima.config;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.PlatformTransactionManager;

import javax.sql.DataSource;

public class JdbcConfig { 
    
    // 获得配置资源(采用${}获得)
    @Value("${jdbc.driver}")
    private String driver;
    @Value("${jdbc.url}")
    private String url;
    @Value("${jdbc.username}")
    private String username;
    @Value("${jdbc.password}")
    private String password;

    // 设置为Bean
    // 配置资源(这里采用的是DruidDataSource)
    @Bean
    public DataSource dataSource(){
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(driver);
        dataSource.setUrl(url);
        dataSource.setUsername(username);
        dataSource.setPassword(password);
        return dataSource;
    }

    // 设置为Bean
    // 配置事务平台(这里采用的是DataSourceTransactionManager)
    @Bean
    public PlatformTransactionManager transactionManager(DataSource dataSource){
        DataSourceTransactionManager ds = new DataSourceTransactionManager();
        ds.setDataSource(dataSource);
        return ds;
    }
}
// MyBatisConfig

package com.itheima.config;

import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.mapper.MapperScannerConfigurer;
import org.springframework.context.annotation.Bean;

import javax.sql.DataSource;

public class MyBatisConfig {

    // 设置为Bean
    // 创建工厂SqlSessionFactory,用于实现数据库交互
    @Bean
    public SqlSessionFactoryBean sqlSessionFactory(DataSource dataSource){
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(dataSource);
        factoryBean.setTypeAliasesPackage("com.itheima.domain");
        return factoryBean;
    }

    // 设置为Bean
    // 创建映射,并定义映射地址,采用MapperScannerConfigurer
    @Bean
    public MapperScannerConfigurer mapperScannerConfigurer(){
        MapperScannerConfigurer msc = new MapperScannerConfigurer();
        msc.setBasePackage("com.itheima.dao");
        return msc;
    }

}
  1. SpringMvcConfig配置类
// SpringMvcConfig

package com.itheima.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;

// Spring配置类
@Configuration
// 扫描包
@ComponentScan("com.itheima.controller")
// 万能工具注解
@EnableWebMvc
public class SpringMvcConfig {
}
// ServletConfig

package com.itheima.config;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

// 注意:继承于AbstractAnnotationConfigDispatcherServletInitializer
public class ServletConfig extends AbstractAnnotationConfigDispatcherServletInitializer {
    // 设置SpringConfig
    protected Class<?>[] getRootConfigClasses() {
        return new Class[]{SpringConfig.class};
    }

    // 设置SpringMvcConfig
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{SpringMvcConfig.class};
    }

    // 设置路径锁定"/"即可
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }
}
  1. 数据库对应实体类创建
// Book

package com.itheima.domain;

public class Book {
    private Integer id;
    private String type;
    private String name;
    private String description;

    @Override
    public String toString() {
        return "Book{" +
                "id=" + id +
                ", type='" + type + '\'' +
                ", name='" + name + '\'' +
                ", description='" + description + '\'' +
                '}';
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }
}
  1. 数据层代码
// BookDao

package com.itheima.dao;

import com.itheima.domain.Book;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import java.util.List;

public interface BookDao {

    // 采用Mapper代理开发
    // 采用#{}匹配参数
    
    @Insert("insert into tbl_book (type,name,description) values(#{type},#{name},#{description})")
    public void save(Book book);

    @Update("update tbl_book set type = #{type}, name = #{name}, description = #{description} where id = #{id}")
    public void update(Book book);

    @Delete("delete from tbl_book where id = #{id}")
    public void delete(Integer id);

    @Select("select * from tbl_book where id = #{id}")
    public Book getById(Integer id);

    @Select("select * from tbl_book")
    public List<Book> getAll();
}
  1. 业务层代码
// BookService

package com.itheima.service;

import com.itheima.domain.Book;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

// 给出事务开启标志
@Transactional
public interface BookService {
    
    // 采用文档注释,表明各方法作用

    /**
     * 保存
     * @param book
     * @return
     */
    public boolean save(Book book);

    /**
     * 修改
     * @param book
     * @return
     */
    public boolean update(Book book);

    /**
     * 按id删除
     * @param id
     * @return
     */
    public boolean delete(Integer id);

    /**
     * 按id查询
     * @param id
     * @return
     */
    public Book getById(Integer id);

    /**
     * 查询全部
     * @return
     */
    public List<Book> getAll();
}
// BookServiceImpl

package com.itheima.service.impl;

import com.itheima.dao.BookDao;
import com.itheima.domain.Book;
import com.itheima.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

// 标记为Bean
@Service
public class BookServiceImpl implements BookService {
    
    // 自动装配
    @Autowired
    private BookDao bookDao;

    public boolean save(Book book) {
        bookDao.save(book);
        return true;
    }

    public boolean update(Book book) {
        bookDao.update(book);
        return true;
    }

    public boolean delete(Integer id) {
        bookDao.delete(id);
        return true;
    }

    public Book getById(Integer id) {
        return bookDao.getById(id);
    }

    public List<Book> getAll() {
        return bookDao.getAll();
    }
}
  1. 服务层代码
package com.itheima.controller;

import com.itheima.domain.Book;
import com.itheima.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

// 标记为Bean
// 采用REST书写方式
@RestController
// 设置总体路径前缀
@RequestMapping("/books")
public class BookController {

	// 自动装配
    @Autowired
    private BookService bookService;

    // 新添采用POST请求
    // 数据位于请求体,采用@RequestBody
    @PostMapping
    public boolean save(@RequestBody Book book) {
        return bookService.save(book);
    }

    // 更新采用PUT请求
    // 数据位于请求体,采用@RequestBody
    @PutMapping
    public boolean update(@RequestBody Book book) {
        return bookService.update(book);
    }

    // 删除采用DELETE请求
    // 数据位于请求路径,采用@PathVariable,并在路径采用{}表示
    @DeleteMapping("/{id}")
    public boolean delete(@PathVariable Integer id) {
        return bookService.delete(id);
    }

    // 访问采用GET请求
    // 数据位于请求路径,采用@PathVariable,并在路径采用{}表示
    @GetMapping("/{id}")
    public Book getById(@PathVariable Integer id) {
        return bookService.getById(id);
    }

    // 访问采用GET请求
    @GetMapping
    public List<Book> getAll() {
        return bookService.getAll();
    }
}

案例测试阶段

  1. Java内部代码测试
// 测试均实现于test文件夹下

package com.itheima.service;

import com.itheima.config.SpringConfig;
import com.itheima.domain.Book;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import java.util.List;

// 测试采用的junit
@RunWith(SpringJUnit4ClassRunner.class)
// 测试采用的配置文件
@ContextConfiguration(classes = SpringConfig.class)
public class BookServiceTest {

    // 自动装配
    @Autowired
    private BookService bookService;

    // 查询id=1的值
    @Test
    public void testGetById(){
        Book book = bookService.getById(1);
        System.out.println(book);
    }

    // 查询所有数据
    @Test
    public void testGetAll(){
        List<Book> all = bookService.getAll();
        System.out.println(all);
    }

}
  1. Postman测试

我们需要采用网页进行测试是否满足需求,下面仅列出简单示例:

案例总结阶段

以上部分就是根据我们之前所学内容所整合出来的整体框架,我们已经基本做成了一个简单的服务器

SSM表现层数据封装

我们在上一小节已经完成了一个基本项目的开发

但是我们会注意到我们服务层的返回数据类型不尽相同:

package com.itheima.controller;

import com.itheima.domain.Book;
import com.itheima.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/books")
public class BookController {

    @Autowired
    private BookService bookService;

    // 我们会注意到我们返回的数据有时为boolean,有时为Book,有时为List<Book>
    
    @PostMapping
    public boolean save(@RequestBody Book book) {
        return bookService.save(book);
    }

    @PutMapping
    public boolean update(@RequestBody Book book) {
        return bookService.update(book);
    }

    @DeleteMapping("/{id}")
    public boolean delete(@PathVariable Integer id) {
        return bookService.delete(id);
    }

    @GetMapping("/{id}")
    public Book getById(@PathVariable Integer id) {
        return bookService.getById(id);
    }

    @GetMapping
    public List<Book> getAll() {
        return bookService.getAll();
    }
}

我们需要注意的是:

  • 项目并非我们一个人开发,我们在实际开发中大部分前后端是分离的,也就是说我们返回的数据是返回给前端进行处理的
  • 但前端并不熟悉后端的代码,所以我们如果毫无忌惮的传递没有任何说明的数据,前端是无法把它做成页面展现出来的
  • 所以前后端通常需要一种规范来设计返回类型,让前端能够明白后端所传递的数据,我们通常把他称为表现层数据封装

表现层数据封装概念

为了保障前后端沟通无障碍,在项目开始时,前后端会进行一次沟通来确定后端传递数据的规范,我们通常把它称为表现层数据封装

我们通常采用一个实现类来规定数据封装格式:

public class Result{
    
    // 这里我们假设给出三种数据来进行前后端沟通
    /*
    data:数据内容
    code:状态码
    msg:相关信息
    */
	private Object data;
    private Integer code;
    private String msg;
}

这里的data数据就是取自表现层数据,code是双方规定的状态码,msg是用于提供相关附属信息

Result类中的字段不是固定的,可以根据需求自行删减

注意需要提供若干个构造方法,方便操作

表现层数据封装操作

接下里我们以第一阶段案例给出相关修改案例:

  1. 设计Code状态码
package com.itheima.controller;

//状态码
//通常是双方协议或公司规定
public class Code {
    public static final Integer SAVE_OK = 20011;
    public static final Integer DELETE_OK = 20021;
    public static final Integer UPDATE_OK = 20031;
    public static final Integer GET_OK = 20041;

    public static final Integer SAVE_ERR = 20010;
    public static final Integer DELETE_ERR = 20020;
    public static final Integer UPDATE_ERR = 20030;
    public static final Integer GET_ERR = 20040;
}
  1. 设计Result返回数据规范
package com.itheima.controller;

public class Result {
    //描述统一格式中的数据
    private Object data;
    //描述统一格式中的编码,用于区分操作,可以简化配置0或1表示成功失败
    private Integer code;
    //描述统一格式中的消息,可选属性
    private String msg;

    // 注意:我们需要提供构造方法便捷操作
    
    public Result() {
    }

    public Result(Integer code,Object data) {
        this.data = data;
        this.code = code;
    }

    public Result(Integer code, Object data, String msg) {
        this.data = data;
        this.code = code;
        this.msg = msg;
    }

    public Object getData() {
        return data;
    }

    public void setData(Object data) {
        this.data = data;
    }

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}
  1. 服务层返回数据更替
package com.itheima.controller;

import com.itheima.domain.Book;
import com.itheima.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

//统一每一个控制器方法返回值
@RestController
@RequestMapping("/books")
public class BookController {

    @Autowired
    private BookService bookService;

    // 我们按照Result的构造方法以及实际需求提供返回值
    // 我们可以根据三目运算符来直接输出其结果
    
    @PostMapping
    public Result save(@RequestBody Book book) {
        boolean flag = bookService.save(book);
        return new Result(flag ? Code.SAVE_OK:Code.SAVE_ERR,flag);
    }

    @PutMapping
    public Result update(@RequestBody Book book) {
        boolean flag = bookService.update(book);
        return new Result(flag ? Code.UPDATE_OK:Code.UPDATE_ERR,flag);
    }

    @DeleteMapping("/{id}")
    public Result delete(@PathVariable Integer id) {
        boolean flag = bookService.delete(id);
        return new Result(flag ? Code.DELETE_OK:Code.DELETE_ERR,flag);
    }

    @GetMapping("/{id}")
    public Result getById(@PathVariable Integer id) {
        Book book = bookService.getById(id);
        Integer code = book != null ? Code.GET_OK : Code.GET_ERR;
        String msg = book != null ? "" : "数据查询失败,请重试!";
        return new Result(code,book,msg);
    }

    @GetMapping
    public Result getAll() {
        List<Book> bookList = bookService.getAll();
        Integer code = bookList != null ? Code.GET_OK : Code.GET_ERR;
        String msg = bookList != null ? "" : "数据查询失败,请重试!";
        return new Result(code,bookList,msg);
    }
}

异常处理器

我们的程序可能或者说必然会出现一些漏洞,有些可能是人为的,有些可能是我们代码的问题

所以为了处理这些异常,首先我们需要把异常出现的常见位置与原因进行分类:

  • 框架内部抛出的异常:因使用不合规导致
  • 数据层抛出的异常:因外部服务器故障导致(例如:服务器访问超时)
  • 业务层抛出的异常:因业务逻辑书写错误导致(例如:遍历业务书写操作,导致索引异常等)
  • 表现层抛出的异常:因数据收集,校验等规则导致(例如:不匹配的数据类型间导致异常)
  • 工具类抛出的异常:因工具类书写不严谨不够健全导致(例如:必要释放的连接长期未释放)

那么我们来思考两个问题来确定异常处理器的书写方法和位置:

  1. 在上述我们可以看到各个层级都会出现问题,那么我们的异常处理器应该写在哪一层?
  • 所有的异常均向上抛出至表现层进行处理
  1. 表现层处理异常,每个方法单独书写,代码书写量巨大且意义不大,该怎么处理?
  • 采用AOP思想

编写基本异常处理器

我们常常会集中的,统一的处理项目中出现的异常

前面我们说过需要在表现层统一处理异常,所以我们选择在表现层书写异常处理器:

package com.itheima.controller;

import com.itheima.exception.BusinessException;
import com.itheima.exception.SystemException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

//@RestControllerAdvice用于标识当前类为REST风格对应的异常处理器
@RestControllerAdvice
public class ProjectExceptionAdvice {
    
    // @ExceptionHandler用于设置当前处理器类对应的异常类型
    // 这里处理的是Exception.class,属于最大的异常处理
    @ExceptionHandler(Exception.class)
    public Result doOtherException(Exception ex){
        // Code.SYSTEM_UNKNOW_ERR是在Code状态码文件中统一设置的,null是返回值,后面属于附加内容用于安抚用户
        return new Result(Code.SYSTEM_UNKNOW_ERR,null,"系统繁忙,请稍后再试!");
    }
}

/*
名称:@RestControllerAdvice
类型:类注解
位置:Rest风格开发的控制器增强类定义上方
作用:为Rest风格开发的控制器类做增强
说明:此注解自带@ResponseBody注解与@Component注解,具备对应的功能

名称:@ExceptionHandler
类型:方法注解
位置:专用于异常处理的控制器方法上方
作用:设置指定异常的处理方案,功能等同于控制器方法,出现异常后终止原始控制器操作,并转入该方法进行执行
说明:此类方法可以根据处理的异常不同,制作多个方法分别处理对应的异常

*/

编写项目异常处理

我们的项目异常处理通常不会直接对最大异常处理

因为我们的项目通常会出现很多种类型的异常,例如用户操作错误产生的异常,编程人员未预期到的异常

我们进行一个简单的分类:

  • 业务异常(BusinessException)
    • 规范的用户行为产生的异常
    • 不规范的用户行为操作产生的异常
  • 系统异常(SystemException)
    • 项目运行过程中可预计且无法避免的异常
  • 其他异常(Exception)
    • 编程人员未预期到的异常

对于不同的异常,我们采用不同的应对方法,我们下面做出简单的处理:

  1. Code状态码增加
package com.itheima.controller;

public class Code {
    public static final Integer SAVE_OK = 20011;
    public static final Integer DELETE_OK = 20021;
    public static final Integer UPDATE_OK = 20031;
    public static final Integer GET_OK = 20041;

    public static final Integer SAVE_ERR = 20010;
    public static final Integer DELETE_ERR = 20020;
    public static final Integer UPDATE_ERR = 20030;
    public static final Integer GET_ERR = 20040;

    public static final Integer SYSTEM_ERR = 50001;
    public static final Integer SYSTEM_TIMEOUT_ERR = 50002;
    public static final Integer SYSTEM_UNKNOW_ERR = 59999;

    public static final Integer BUSINESS_ERR = 60002;
}
  1. 书写自定义异常处理器
// SystemException

package com.itheima.exception;
//自定义异常处理器,用于封装异常信息,对异常进行分类,需要继承RuntimeException
public class SystemException extends RuntimeException{
    private Integer code;

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public SystemException(Integer code, String message) {
        super(message);
        this.code = code;
    }

    public SystemException(Integer code, String message, Throwable cause) {
        super(message, cause);
        this.code = code;
    }

}
// BusinessException

package com.itheima.exception;
//自定义异常处理器,用于封装异常信息,对异常进行分类,需要继承RuntimeException
public class BusinessException extends RuntimeException{
    private Integer code;

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public BusinessException(Integer code, String message) {
        super(message);
        this.code = code;
    }

    public BusinessException(Integer code, String message, Throwable cause) {
        super(message, cause);
        this.code = code;
    }

}
  1. 这里选择在业务层抛出异常
package com.itheima.service.impl;

import com.itheima.controller.Code;
import com.itheima.dao.BookDao;
import com.itheima.domain.Book;
import com.itheima.exception.BusinessException;
import com.itheima.exception.SystemException;
import com.itheima.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class BookServiceImpl implements BookService {
    @Autowired
    private BookDao bookDao;

    public boolean save(Book book) {
        bookDao.save(book);
        return true;
    }

    public boolean update(Book book) {
        bookDao.update(book);
        return true;
    }

    public boolean delete(Integer id) {
        bookDao.delete(id);
        return true;
    }

    public Book getById(Integer id) {
        //模拟业务异常,包装成自定义异常
        if(id == 1){
            throw new BusinessException(Code.BUSINESS_ERR,"请不要使用你的技术挑战我的耐性!");
        }
        //模拟系统异常,将可能出现的异常进行包装,转换成自定义异常
        try{
            int i = 1/0;
        }catch (Exception e){
            throw new SystemException(Code.SYSTEM_TIMEOUT_ERR,"服务器访问超时,请重试!",e);
        }
        return bookDao.getById(id);
    }

    public List<Book> getAll() {
        return bookDao.getAll();
    }
}
  1. 表现层异常处理器增加
package com.itheima.controller;

import com.itheima.exception.BusinessException;
import com.itheima.exception.SystemException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

//@RestControllerAdvice用于标识当前类为REST风格对应的异常处理器
@RestControllerAdvice
public class ProjectExceptionAdvice {
    //@ExceptionHandler用于设置当前处理器类对应的异常类型
    @ExceptionHandler(SystemException.class)
    public Result doSystemException(SystemException ex){
        //记录日志
        //发送消息给运维
        //发送邮件给开发人员,ex对象发送给开发人员
        return new Result(ex.getCode(),null,ex.getMessage());
    }

    @ExceptionHandler(BusinessException.class)
    public Result doBusinessException(BusinessException ex){
        return new Result(ex.getCode(),null,ex.getMessage());
    }

    //除了自定义的异常处理器,保留对Exception类型的异常处理,用于处理非预期的异常
    @ExceptionHandler(Exception.class)
    public Result doOtherException(Exception ex){
        //记录日志
        //发送消息给运维
        //发送邮件给开发人员,ex对象发送给开发人员
        return new Result(Code.SYSTEM_UNKNOW_ERR,null,"系统繁忙,请稍后再试!");
    }
}

前后端协议联调

在定义了前后端的协议规范并完成了后端开发后,我们还需要设计前端的开发

关于前端开发并不是我们的重点,所以下面只作简单介绍

拦截器设置

首先我们需要注意我们的SpringMVC的拦截路径设置为全部路径:

// ServletContainersInitConfig

package com.itheima.config;

import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

import javax.servlet.Filter;

public class ServletContainersInitConfig extends AbstractAnnotationConfigDispatcherServletInitializer {
    protected Class<?>[] getRootConfigClasses() {
        return new Class[0];
    }

    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{SpringMvcConfig.class};
    }

    protected String[] getServletMappings() {
        // 系统会将全部路径下的请求都交付给SpringMVC处理
        return new String[]{"/"};
    }

    //乱码处理
    @Override
    protected Filter[] getServletFilters() {
        CharacterEncodingFilter filter = new CharacterEncodingFilter();
        filter.setEncoding("UTF-8");
        return new Filter[]{filter};
    }
}

所以当我们查询主页网页时,会被SpringMVC接收并且要求返回一个相关的服务层方法,很明显这是错误的

所以我们需要设置一个拦截器用来放行一些网页相关的资源,使用户访问时,直接将相关页面资源反馈回去:

// 我们选择在Config文件夹下创建SpringMvcSupport继承WebMvcConfigurationSupport作为SpringMVC的工具类

package com.itheima.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;

// 需要继承WebMvcConfigurationSupport用作工具类
@Configuration
public class SpringMvcSupport extends WebMvcConfigurationSupport {
    
    // 继承addResourceHandlers方法,进行放行操作
    @Override
    protected void addResourceHandlers(ResourceHandlerRegistry registry) {
        // 利用参数registry,addResourceHandler后跟参数路径,addResourceLocations后跟访问页面
        registry.addResourceHandler("/pages/**").addResourceLocations("/pages/");
        registry.addResourceHandler("/css/**").addResourceLocations("/css/");
        registry.addResourceHandler("/js/**").addResourceLocations("/js/");
        registry.addResourceHandler("/plugins/**").addResourceLocations("/plugins/");
    }
}

同时记得在SpringMvcConfig中扫描相关类:

// SpringMvcConfig

package com.itheima.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;

@Configuration
@ComponentScan({"com.itheima.controller","com.itheima.config"})
@EnableWebMvc
public class SpringMvcConfig {
}

前端操作简单讲解

当我们设置好拦截器后,我们就可以通过页面访问进入到html主页:

我们希望可以实现查询,创建,修改,删除等操作

在下述操作中我们采用html和Ajax两门技术实现上述操作:

  1. 首先我们需要在Dao数据层进行一些返回值的修改:
package com.itheima.dao;

import com.itheima.domain.Book;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import java.util.List;

public interface BookDao {
    // 我们采用int作为返回值,当作数据库操作的行数返回值,用来判断是否操作成功

    @Insert("insert into tbl_book (type,name,description) values(#{type},#{name},#{description})")
    public int save(Book book);

    @Update("update tbl_book set type = #{type}, name = #{name}, description = #{description} where id = #{id}")
    public int update(Book book);

    @Delete("delete from tbl_book where id = #{id}")
    public int delete(Integer id);

    @Select("select * from tbl_book where id = #{id}")
    public Book getById(Integer id);

    @Select("select * from tbl_book")
    public List<Book> getAll();
}
  1. 我们对html页面进行操作:
<!DOCTYPE html>

<html>

    <head>

        <!-- 页面meta -->

        <meta charset="utf-8">

        <meta http-equiv="X-UA-Compatible" content="IE=edge">

        <title>SpringMVC案例</title>

        <meta content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=no" name="viewport">

        <!-- 引入样式 -->

        <link rel="stylesheet" href="../plugins/elementui/index.css">

        <link rel="stylesheet" href="../plugins/font-awesome/css/font-awesome.min.css">

        <link rel="stylesheet" href="../css/style.css">

    </head>

    <body class="hold-transition">

        <div id="app">

            <div class="content-header">

                <h1>图书管理</h1>

            </div>

            <div class="app-container">

                <div class="box">

                    <div class="filter-container">

                        <el-input placeholder="图书名称" v-model="pagination.queryString" style="width: 200px;" class="filter-item"></el-input>

                        <el-button @click="getAll()" class="dalfBut">查询</el-button>

                        <el-button type="primary" class="butT" @click="handleCreate()">新建</el-button>

                    </div>

                    <el-table size="small" current-row-key="id" :data="dataList" stripe highlight-current-row>

                        <el-table-column type="index" align="center" label="序号"></el-table-column>

                        <el-table-column prop="type" label="图书类别" align="center"></el-table-column>

                        <el-table-column prop="name" label="图书名称" align="center"></el-table-column>

                        <el-table-column prop="description" label="描述" align="center"></el-table-column>

                        <el-table-column label="操作" align="center">

                            <template slot-scope="scope">

                                <el-button type="primary" size="mini" @click="handleUpdate(scope.row)">编辑</el-button>

                                <el-button type="danger" size="mini" @click="handleDelete(scope.row)">删除</el-button>

                            </template>

                        </el-table-column>

                    </el-table>

                    <!-- 新增标签弹层 -->

                    <div class="add-form">

                        <el-dialog title="新增图书" :visible.sync="dialogFormVisible">

                            <el-form ref="dataAddForm" :model="formData" :rules="rules" label-position="right" label-width="100px">

                                <el-row>

                                    <el-col :span="12">

                                        <el-form-item label="图书类别" prop="type">

                                            <el-input v-model="formData.type"/>

                                        </el-form-item>

                                    </el-col>

                                    <el-col :span="12">

                                        <el-form-item label="图书名称" prop="name">

                                            <el-input v-model="formData.name"/>

                                        </el-form-item>

                                    </el-col>

                                </el-row>


                                <el-row>

                                    <el-col :span="24">

                                        <el-form-item label="描述">

                                            <el-input v-model="formData.description" type="textarea"></el-input>

                                        </el-form-item>

                                    </el-col>

                                </el-row>

                            </el-form>

                            <div slot="footer" class="dialog-footer">

                                <el-button @click="dialogFormVisible = false">取消</el-button>

                                <el-button type="primary" @click="handleAdd()">确定</el-button>

                            </div>

                        </el-dialog>

                    </div>

                    <!-- 编辑标签弹层 -->

                    <div class="add-form">

                        <el-dialog title="编辑检查项" :visible.sync="dialogFormVisible4Edit">

                            <el-form ref="dataEditForm" :model="formData" :rules="rules" label-position="right" label-width="100px">

                                <el-row>

                                    <el-col :span="12">

                                        <el-form-item label="图书类别" prop="type">

                                            <el-input v-model="formData.type"/>

                                        </el-form-item>

                                    </el-col>

                                    <el-col :span="12">

                                        <el-form-item label="图书名称" prop="name">

                                            <el-input v-model="formData.name"/>

                                        </el-form-item>

                                    </el-col>

                                </el-row>

                                <el-row>

                                    <el-col :span="24">

                                        <el-form-item label="描述">

                                            <el-input v-model="formData.description" type="textarea"></el-input>

                                        </el-form-item>

                                    </el-col>

                                </el-row>

                            </el-form>

                            <div slot="footer" class="dialog-footer">

                                <el-button @click="dialogFormVisible4Edit = false">取消</el-button>

                                <el-button type="primary" @click="handleEdit()">确定</el-button>

                            </div>

                        </el-dialog>

                    </div>

                </div>

            </div>

        </div>

    </body>

    <!-- 引入组件库 -->

    <script src="../js/vue.js"></script>

    <script src="../plugins/elementui/index.js"></script>

    <script type="text/javascript" src="../js/jquery.min.js"></script>

    <script src="../js/axios-0.18.0.js"></script>

    <script>
        var vue = new Vue({

            el: '#app',
            data:{
                pagination: {},
				dataList: [],//当前页要展示的列表数据
                formData: {},//表单数据
                dialogFormVisible: false,//控制表单是否可见
                dialogFormVisible4Edit:false,//编辑表单是否可见
                rules: {//校验规则
                    type: [{ required: true, message: '图书类别为必填项', trigger: 'blur' }],
                    name: [{ required: true, message: '图书名称为必填项', trigger: 'blur' }]
                }
            },

            //钩子函数,VUE对象初始化完成后自动执行
            created() {
                this.getAll();
            },

            methods: {
                //列表
                getAll() {
                    //发送ajax请求
                    axios.get("/books").then((res)=>{
                        this.dataList = res.data.data;
                    });
                },

                //弹出添加窗口
                handleCreate() {
                    this.dialogFormVisible = true;
                    this.resetForm();
                },

                //重置表单
                resetForm() {
                    this.formData = {};
                },

                //添加
                handleAdd () {
                    //发送ajax请求
                    axios.post("/books",this.formData).then((res)=>{
                        console.log(res.data);
                        //如果操作成功,关闭弹层,显示数据
                        if(res.data.code == 20011){
                            this.dialogFormVisible = false;
                            this.$message.success("添加成功");
                        }else if(res.data.code == 20010){
                            this.$message.error("添加失败");
                        }else{
                            this.$message.error(res.data.msg);
                        }
                    }).finally(()=>{
                        this.getAll();
                    });
                },

                //弹出编辑窗口
                handleUpdate(row) {
                    // console.log(row);   //row.id 查询条件
                    //查询数据,根据id查询
                    axios.get("/books/"+row.id).then((res)=>{
                        // console.log(res.data.data);
                        if(res.data.code == 20041){
                            //展示弹层,加载数据
                            this.formData = res.data.data;
                            this.dialogFormVisible4Edit = true;
                        }else{
                            this.$message.error(res.data.msg);
                        }
                    });
                },

                //编辑
                handleEdit() {
                    //发送ajax请求
                    axios.put("/books",this.formData).then((res)=>{
                        //如果操作成功,关闭弹层,显示数据
                        if(res.data.code == 20031){
                            this.dialogFormVisible4Edit = false;
                            this.$message.success("修改成功");
                        }else if(res.data.code == 20030){
                            this.$message.error("修改失败");
                        }else{
                            this.$message.error(res.data.msg);
                        }
                    }).finally(()=>{
                        this.getAll();
                    });
                },

                // 删除
                handleDelete(row) {
                    //1.弹出提示框
                    this.$confirm("此操作永久删除当前数据,是否继续?","提示",{
                        type:'info'
                    }).then(()=>{
                        //2.做删除业务
                        axios.delete("/books/"+row.id).then((res)=>{
                            if(res.data.code == 20021){
                                this.$message.success("删除成功");
                            }else{
                                this.$message.error("删除失败");
                            }
                        }).finally(()=>{
                            this.getAll();
                        });
                    }).catch(()=>{
                        //3.取消删除
                        this.$message.info("取消删除操作");
                    });
                }
            }
        })

    </script>

</html>

拦截器

我们在前面已经接触到了拦截器,在这一节中我们详细介绍一下拦截器

拦截器定义:

  • 一种动态拦截方法调用的机制

拦截器作用:

  • 在指定的方法调用前后执行预先设定的代码
  • 阻止原始方法的执行

拦截器的大概图示如下:

简单讲解:

  • html发送的所有数据被Tomcat所接收
  • 对于静态数据我们直接归纳于静态资源中不做处理
  • 对于动态资源,我们先通过Filter过滤器进行过滤,然后才进入到Spring阶段进行处理
  • 进入Spring阶段之后,我们开始进行处理,但在对Controller服务层进行操作前,需要进行的检测或者补充内容就是拦截器

拦截器和过滤器的区别:

归属不同:Filter属于Servlet技术,Interceptor属于SpringMVC技术

拦截内容不同:Filter对所有访问进行增强,Interceptor仅针对SpringMVC的访问进行增强

拦截器入门案例

我们同样采用一个案例来进行拦截器的讲解:

  1. 创建拦截器(我们通常在Controller文件夹下创建一个Interceptor文件夹来存放各种拦截器)
// src/main/java/com/itheima/controller/interceptor/ProjectInterceptor.java

package com.itheima.controller.interceptor;

import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
//定义拦截器类,实现HandlerInterceptor接口
//注意当前类必须受Spring容器控制(采用@Component)
public class ProjectInterceptor implements HandlerInterceptor {
    @Override
    //原始方法调用前执行的内容
    //返回值类型可以拦截控制的执行,true放行,false终止
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...");
        return true;
    }

    @Override
    //原始方法调用后执行的内容
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }

    @Override
    //原始方法调用完成后执行的内容
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }
}
  1. 创建拦截路径(在SpringMvcSupport中操作)
package com.itheima.config;

import com.itheima.controller.interceptor.ProjectInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;

@Configuration
public class SpringMvcSupport extends WebMvcConfigurationSupport {
    
    // 这里我们自动装配我们之前配置过的拦截器
    @Autowired
    private ProjectInterceptor projectInterceptor;

    @Override
    protected void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/pages/**").addResourceLocations("/pages/");
    }

    // 我们继承实现addInterceptors方法添加拦截
    @Override
    protected void addInterceptors(InterceptorRegistry registry) {
        //配置拦截器(addInterceptor后面跟拦截器,addPathPatterns后面跟拦截路径)
        registry.addInterceptor(projectInterceptor).addPathPatterns("/books","/books/*");
    }
}
  1. 记得在SpringMvcConfig中添加扫描路径
package com.itheima.config;

import com.itheima.controller.interceptor.ProjectInterceptor;
import com.itheima.controller.interceptor.ProjectInterceptor2;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
@ComponentScan({"com.itheima.controller","com.itheima.config"})
@EnableWebMvc
//实现WebMvcConfigurer接口可以简化开发,但具有一定的侵入性
public class SpringMvcConfig implements WebMvcConfigurer {
}

拦截器入门案例简化开发

上述是我们正常开发的流程,但实际上我们还存在一种简化开发的方法:

  1. 创建拦截器(不发生变化)
// src/main/java/com/itheima/controller/interceptor/ProjectInterceptor.java

package com.itheima.controller.interceptor;

import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
//定义拦截器类,实现HandlerInterceptor接口
//注意当前类必须受Spring容器控制(采用@Component)
public class ProjectInterceptor implements HandlerInterceptor {
    @Override
    //原始方法调用前执行的内容
    //返回值类型可以拦截控制的执行,true放行,false终止
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...");
        return true;
    }

    @Override
    //原始方法调用后执行的内容
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }

    @Override
    //原始方法调用完成后执行的内容
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }
}
  1. 我们直接在SpringMvcConfig中实现拦截方法的添加
package com.itheima.config;

import com.itheima.controller.interceptor.ProjectInterceptor;
import com.itheima.controller.interceptor.ProjectInterceptor2;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
@ComponentScan({"com.itheima.controller"})
@EnableWebMvc
// 直接继承WebMvcConfigurer接口,实现内部方法即可
//实现WebMvcConfigurer接口可以简化开发,但具有一定的侵入性
public class SpringMvcConfig implements WebMvcConfigurer {
    @Autowired
    private ProjectInterceptor projectInterceptor;

    // 实现addInterceptors方法,添加拦截器
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(projectInterceptor).addPathPatterns("/books","/books/*");
    }
}

拦截器执行过程

我们在前面介绍了拦截器的相关代码,现在我们来简单介绍一下拦截器的执行过程:

package com.itheima.controller.interceptor;

import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
public class ProjectInterceptor implements HandlerInterceptor {
    @Override
    //原始方法调用前执行的内容
    //返回值类型可以拦截控制的执行,true放行,false终止
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...");
        return true;
    }

    @Override
    //原始方法调用后执行的内容
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }

    @Override
    //原始方法调用完成后执行的内容
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }
}

根据上述代码,我们可以基本确定其执行顺序为:

注意:当PreHandle反馈出false时,所有后续操作均失效!

拦截器参数

拦截器一共分为三个方法,接下来我们对方法中的各个参数进行解释:

  1. 前置处理
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 我们可以根据request,response获得网页交互信息
        String contentType = request.getHeader("Content-Type");
        // 我们可以根据handler转换类型为HandlerMethod,从而完成了一些暴力反射操作
        HandlerMethod hm = (HandlerMethod)handler;
        System.out.println("preHandle..."+contentType);
        return true;
    }

参数:

  • request:请求对象
  • response:响应对象
  • handler:被调用的处理器对象,本质上是一个方法对象,对反射技术中的Method对象进行了再包装

返回值:

  • 返回值为true,后续操作执行
  • 返回值为false,后续操作不执行
  1. 后置处理
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }

参数:

  • modelAndView:如果处理器执行完成具有返回结果,可以读取到对应数据与页面信息进行调整(了解即可)
  1. 完成后操作
    @Override
    //原始方法调用完成后执行的内容
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }

参数:

  • ex:如果处理器执行过程中出现异常对象,可以针对异常情况进行单独处理(了解即可)

拦截器链配置

拦截器和过滤器同样,可以配置多个,也具有一定的拦截顺序

我们先给出代码展示:

  1. 拦截器设置:
package com.itheima.controller.interceptor;

import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
public class ProjectInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...);
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }
}
package com.itheima.controller.interceptor;

import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
public class ProjectInterceptor2 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...222");
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...222");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...222");
    }
}
  1. 拦截器添加
package com.itheima.config;

import com.itheima.controller.interceptor.ProjectInterceptor;
import com.itheima.controller.interceptor.ProjectInterceptor2;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
@ComponentScan({"com.itheima.controller"})
@EnableWebMvc
//实现WebMvcConfigurer接口可以简化开发,但具有一定的侵入性
public class SpringMvcConfig implements WebMvcConfigurer {
    @Autowired
    private ProjectInterceptor projectInterceptor;
    @Autowired
    private ProjectInterceptor2 projectInterceptor2;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //配置多拦截器
        registry.addInterceptor(projectInterceptor).addPathPatterns("/books","/books/*");
        registry.addInterceptor(projectInterceptor2).addPathPatterns("/books","/books/*");
    }
}

经过测试,我们可以发现:

// 正常运行
preHandle...
preHandle...222
具体操作...
postHandle...222
postHandle...
afterCompletion...222
afterCompletion...
// 拦截器2出错
preHandle...
preHandle...222
afterCompletion...
// 拦截器1出错
preHandle...

三层拦截器具体操作图:

所以我们可以总结出相关规定:

  • 当配置多个拦截器时,形成拦截器链
  • 拦截器链的运行顺序参照拦截器的添加顺序为准
  • 当拦截器中出现对原始处理器的拦截,后面的拦截器均终止运行
  • 当拦截器运行中断,仅运行配置在前面的拦截器的afterCompletion操作

结束语

好的,关于SSM整合的内容就介绍到这里,希望能为你带来帮助!

附录

该文章属于学习内容,具体参考B站黑马程序员李老师的SSM框架课程

这里附上链接:SpringMVC-17-SSM整合(整合配置)_哔哩哔哩_bilibili

分类:

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