如何将 Spring Boot 与 MySQL 数据库和 JPA 一起使用？

Question

我想用 MySQL 和 JPA 设置 Spring Boot。为此，我创建： 人

package domain;

import javax.persistence.*;

@Entity
@Table(name = "person")
public class Person {

@Id
@GeneratedValue
private Long id;

@Column(nullable = false)
private String firstName;

// setters and getters
}

PersonRepository

package repository;

import domain.Person;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.repository.CrudRepository;


public interface PersonRepository extends CrudRepository<Person, Long> {

Page<Person> findAll(Pageable pageable);
}

PersonController

package controller;

import domain.Person;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import repository.PersonRepository;

@Controller
public class PersonController {

@Autowired
private PersonRepository personRepository;

@RequestMapping("/")
@ResponseBody
public String test() {
    Person person = new Person();
    person.setFirstName("First");
    person.setLastName("Test");
    personRepository.save(person);
    return "hello";
}
}

开始类示例：

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

@SpringBootApplication
public class Example {

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

}

对于数据库配置，我创建 application.properties

spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.properties.hibernate.globally_quoted_identifiers=true

spring.datasource.url=jdbc:mysql://localhost/test_spring_boot
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driverClassName=com.mysql.jdbc.Driver

所以我有项目结构：

但结果我有例外：

org.springframework.beans.factory.BeanDefinitionStoreException: Failed to parse configuration class [Example]; nested exception is java.io.FileNotFoundException: class path resource [org/springframework/security/config/annotation/authentication/configurers/GlobalAuthenticationConfigurerAdapter.class] cannot be opened because it does not exist

作为一个例子，我使用：spring-boot-sample-data-jpa/pom.xml

Answer 1

我像你一样创建了一个项目。结构是这样的

这些课程只是从您的课程中复制粘贴而来。

我将 application.properties 更改为：

spring.datasource.url=jdbc:mysql://localhost/testproject
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.jpa.hibernate.ddl-auto=update

但我认为您的问题出在您的 pom.xml 中：

<?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>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.4.1.RELEASE</version>
</parent>

<artifactId>spring-boot-sample-jpa</artifactId>
<name>Spring Boot JPA Sample</name>
<description>Spring Boot JPA Sample</description>

<dependencies>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
</dependencies>
<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

检查这些文件是否存在差异。希望这会有所帮助

更新 1：我更改了用户名。该示例的链接现在是https://github.com/Yannic92/stackOverflowExamples/tree/master/SpringBoot/MySQL

Answer 2

将类移动到特定包（如存储库、控制器、域）时，仅通用 @SpringBootApplication 是不够的。

您必须指定组件扫描的基本包

@ComponentScan("base_package")

对于 JPA

@EnableJpaRepositories(basePackages = "repository")

也是需要的，所以 spring data 会知道在哪里寻找存储库接口。

Answer 3

在spring boot reference，它说：

当一个类不包含包声明时，它被认为是在“默认包”中。通常不鼓励使用“默认包”，应避免使用。对于使用 @ComponentScan、@EntityScan 或 @SpringBootApplication 注解的 Spring Boot 应用程序，它可能会导致特定问题，因为每个 jar 中的每个类都会被读取。

com
 +- example
     +- myproject
         +- Application.java
         |
         +- domain
         |   +- Customer.java
         |   +- CustomerRepository.java
         |
         +- service
         |   +- CustomerService.java
         |
         +- web
             +- CustomerController.java

在你的情况下。你必须在@SpringBootApplication注解中添加scanBasePackages。就像@SpringBootApplication(scanBasePackages={"domain","contorller"..})一样

Answer 4

对于基于 Jpa 的应用程序：基础包扫描 @EnableJpaRepositories(basePackages = "repository") 您可以尝试一次！！！
项目结构

com
 +- stack
     +- app
     |   +- Application.java
     +- controller
     |   +- EmployeeController.java
     +- service
     |   +- EmployeeService.java
     +- repository
     |   +- EmployeeRepository.java
     +- model
     |   +- Employee.java
-pom.xml
dependencies: 
    mysql, lombok, data-jpa

application.properties

#Data source :
spring.datasource.url=jdbc:mysql://localhost:3306/employee?useSSL=false
spring.datasource.username=root
spring.datasource.password=root
spring.jpa.generate-ddl=true
spring.datasource.driverClassName=com.mysql.jdbc.Driver

#Jpa/Hibernate :
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect
spring.jpa.hibernate.ddl-auto = update

Employee.java

@Entity
@Table (name = "employee")
@Getter
@Setter
public class Employee {

    @Id
    @GeneratedValue (strategy = GenerationType.IDENTITY)
    private Long id;

    @Column (name = "first_name")
    private String firstName;
    @Column (name = "last_name")
    private String lastName;
    @Column (name = "email")
    private String email;
    @Column (name = "phone_number")
    private String phoneNumber;
    @Column (name = "emp_desg")
    private String desgination;
}

EmployeeRepository.java

@Repository
public interface EmployeeRepository extends JpaRepository<Employee, Long> {
}

EmployeeController.java

@RestController
public class EmployeeController {

    @Autowired
    private EmployeeService empService;

    @GetMapping (value = "/employees")
    public List<Employee> getAllEmployee(){
        return empService.getAllEmployees();
    }

    @PostMapping (value = "/employee")
    public ResponseEntity<Employee> addEmp(@RequestBody Employee emp, HttpServletRequest 
                                         request) throws URISyntaxException {
        HttpHeaders headers = new HttpHeaders();
        headers.setLocation(new URI(request.getRequestURI() + "/" + emp.getId()));
        empService.saveEmployee(emp);
        return new ResponseEntity<Employee>(emp, headers, HttpStatus.CREATED);
    }

EmployeeService.java

public interface EmployeeService {
    public List<Employee> getAllEmployees();
    public Employee saveEmployee(Employee emp);
}

EmployeeServiceImpl.java

@Service
@Transactional
public class EmployeeServiceImpl implements EmployeeService {

    @Autowired
    private EmployeeRepository empRepository;

    @Override
    public List<Employee> getAllEmployees() {
        return empRepository.findAll();
    }

    @Override
    public Employee saveEmployee(Employee emp) {
        return empRepository.save(emp);
    }
}

EmployeeApplication.java

@SpringBootApplication
@EnableJpaRepositories(basePackages = "repository")
public class EmployeeApplication {
    public static void main(String[] args) {
        SpringApplication.run(EmployeeApplication.class, args);
    }
}

Answer 5

您的代码在默认包中，即您在 src/main/java 中拥有所有文件，但没有自定义包。我强烈建议你创建包 n 然后将源文件放入其中。

Ex-
 src->
     main->
          java->
                com.myfirst.example
                   Example.java
                com.myfirst.example.controller
                   PersonController.java
                com.myfirst.example.repository
                  PersonRepository.java
                com.myfirst.example.model
                   Person.java

希望它能解决你的问题。

Answer 6

请添加mysql-connector-java依赖

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>

并在 application.properties

中添加以下提到的属性

# Data Source properties
spring.datasource.url=jdbc:mysql://localhost:3306/yourDatabaseName?useSSL=false
spring.datasource.username=root
spring.datasource.password=YourPassword
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

# JPA properties 
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect
spring.jpa.show-sql=true
# Hibernate ddl auto (create, create-drop, validate, update)
spring.jpa.hibernate.ddl-auto = update

Answer 7

您可以将Application.java移动到java下的文件夹中。