无法使用spring boot连接到mysql数据库答案

【问题标题】：cant connect to mysql databse using spring boot无法使用spring boot连接到mysql数据库
【发布时间】：2020-09-03 03:55:54
【问题描述】：

当我在 Postman 中点击 url(http://localhost:8080/pjt/samples) 获取 json 数据时，它显示以下错误。

{
    "timestamp": "2020-05-17T10:54:26.705+0000",
    "status": 404,
    "error": "Not Found",
    "message": "No message available",
    "path": "/pjt/samples"
}

1)pom.xml

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.7.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>samplepjt</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>samplepjt</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

2)型号：

package model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "samples")
public class Sample {
    private Long id ;
    private String  name;
    private String city;

    public Sample(String name, String city) {

        this.name = name;
        this.city = city;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }

    @Column(name = "name", nullable = false)
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @Column(name = "city", nullable = false)
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }

    @Override
    public String toString() {
        return "Sample [id=" + id + ",name=" + name + ", city=" + city +  "]";
    }
}

3)存储库

package repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import model.Sample;

@Repository
public interface SampleRepository  extends JpaRepository<Sample,Long>{

}

4)控制器

package controller;

import java.util.List;
import javax.validation.Valid;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import model.Sample;
import repository.SampleRepository;

@RestController
@RequestMapping("/pjt")
public class SampleController {

    @Autowired
    private SampleRepository sampleRepository;

     @PostMapping("/samples")
        public Sample createSample(@Valid @RequestBody Sample sample) {
            return sampleRepository.save(sample);
        }

     @GetMapping("/samples")
        public List<Sample> getAllSample() {
            return sampleRepository.findAll();
        }
    }

5)主函数

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SamplepjtApplication {

    public static void main(String[] args) {
        SpringApplication.run(SamplepjtApplication.class, args);
    }

}

6)application.properties

spring.datasource.url = jdbc:mysql://localhost:3306/sampledb?useSSL=false
spring.datasource.username = root
spring.datasource.password = dali

spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5InnoDBDialect
spring.jpa.hibernate.ddl-auto = update

。 ____ _ __ _ _ /\ / ' __ _ ()_ __ __ _ \ \ \ \ ( ( )_ | '_ | '| | ' / ` | \ \ \ \ \/ )| |)| | | | | || (||))))) ' |____| .|| ||| |__, | / / / / =========|_|===============|___/=///_/ :: Spring Boot :: (v2.2.7.RELEASE)

2020-05-17 16:47:56.159 INFO 3688 --- [main] com.example.demo.SamplepjtApplication：未设置活动配置文件，回退到默认配置文件：默认
2020-05-17 16:47:58.395 INFO 3688 --- [main] .s.d.r.c.RepositoryConfigurationDelegate：在默认模式下引导 Spring Data JPA 存储库。
2020-05-17 16:47:58.476 INFO 3688 --- [main] .s.d.r.c.RepositoryConfigurationDelegate：在 49 毫秒内完成 Spring 数据存储库扫描。找到 0 个 JPA 存储库接口。
2020-05-17 16:48:00.119 INFO 3688 --- [main] o.s.b.w.embedded.tomcat.TomcatWebServer：Tomcat 使用端口初始化：8081 (http)
2020-05-17 16:48:00.142 INFO 3688 --- [main] o.apache.catalina.core.StandardService：启动服务 [Tomcat]
2020-05-17 16:48:00.143 INFO 3688 --- [main] org.apache.catalina.core.StandardEngine：启动 Servlet 引擎：[Apache Tomcat/9.0.34]
2020-05-17 16:48:00.496 INFO 3688 --- [main] o.a.c.c.C.[Tomcat].[localhost].[/]：初始化 Spring 嵌入式 WebApplicationContext
2020-05-17 16:48:00.497 INFO 3688 --- [main] os.web.context.ContextLoader：根 WebApplicationContext：初始化在 4199 毫秒内完成
2020-05-17 16:48:00.980 INFO 3688 --- [main] o.hibernate.jpa.internal.util.LogHelper：HHH000204：处理 PersistenceUnitInfo [名称：默认值]
2020-05-17 16:48:01.156 INFO 3688 --- [main] org.hibernate.Version : HHH000412: Hibernate ORM 核心版本 5.4.15.Final
2020-05-17 16:48:01.579 INFO 3688 --- [main] o.hibernate.annotations.common.Version : HCANN000001: Hibernate Commons Annotations {5.1.0.Final}
2020-05-17 16:48:01.898 INFO 3688 --- [main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - 开始...
2020-05-17 16:48:02.714 INFO 3688 --- [main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - 开始完成。
2020-05-17 16:48:02.771 INFO 3688 --- [main] org.hibernate.dialect.Dialect：HHH000400：使用方言：org.hibernate.dialect.MySQL5InnoDBDialect
2020-05-17 16:48:03.635 INFO 3688 --- [main] o.h.e.t.j.p.i.JtaPlatformInitiator：HHH000490：使用 JtaPlatform 实现：[org.hibernate.engine.transaction.jta.platform.internal.NoJtaPlatform]
2020-05-17 16:48:03.660 INFO 3688 --- [main] j.LocalContainerEntityManagerFactoryBean：为持久性单元“默认”初始化了 JPA EntityManagerFactory
2020-05-17 16:48:04.042 WARN 3688 --- [main] JpaBaseConfiguration$JpaWebConfiguration：spring.jpa.open-in-view 默认启用。因此，可以在视图渲染期间执行数据库查询。显式配置 spring.jpa.open-in-view 以禁用此警告
2020-05-17 16:48:04.388 INFO 3688 --- [main] os.s.concurrent.ThreadPoolTaskExecutor：初始化 ExecutorService 'applicationTaskExecutor'
2020-05-17 16:48:04.845 INFO 3688 --- [main] o.s.b.w.embedded.tomcat.TomcatWebServer：Tomcat 在端口：8081 (http) 上启动，上下文路径为“”
2020-05-17 16:48:04.849 INFO 3688 --- [main] com.example.demo.SamplepjtApplication：在 9.906 秒内启动 SamplepjtApplication（JVM 运行时间为 12.757）
2020-05-17 16:48:13.367 INFO 3688 --- [nio-8081-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/]：初始化 Spring DispatcherServlet 'dispatcherServlet'
2020-05-17 16:48:13.369 INFO 3688 --- [nio-8081-exec-2] os.web.servlet.DispatcherServlet：初始化 Servlet 'dispatcherServlet'
2020-05-17 16:48:13.395 INFO 3688 --- [nio-8081-exec-2] os.web.servlet.DispatcherServlet：在 25 毫秒内完成初始化

谁能帮我解决这个问题？

【问题讨论】：

ComponentScan 不会接您的任何课程。移动根包 com.example.demo 下的类/包。例如：com.example.demo.controller。 @SpringBootApplication 注解会以当前包为根包进行组件扫描，除非另有说明。
或者您可以在@ComponentScan(basePackageClasses = {model.Sample.class, repository.SampleRepository.clas, ...}) 中添加所有这些bean。但这不是一个好的解决方案，项目层次结构要好得多。

标签： java spring hibernate spring-boot jpa

【解决方案1】：

您必须将SampleController.java 放入com.example.demo.controller 和SampleRepository.java 放入com.example.demo.repository。或者所有文件都应该在com.example.demo 文件夹中。

因为@SpringBootApplication 必须扫描所有组件。阅读此文档以更好地理解https://docs.spring.io/spring-boot/docs/2.0.0.RELEASE/reference/html/using-boot-structuring-your-code.html。

【讨论】：