sping boot与JPA结合使用

news2025/1/11 7:52:31

1、pom.xml文件内容如下：

<?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>3.1.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.hmblogs</groupId>
    <artifactId>backend</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>backend</name>
    <description>backend</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

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

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

    </dependencies>

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

</project>

maven重新加载包后，依赖包如下所示：

2、整理代码结构

2.1Dao层，继承JpaRepository就好

package com.hmblogs.backend.dao;

import com.hmblogs.backend.entity.Girl;
import org.springframework.data.jpa.repository.JpaRepository;

//其中第二个参数为Id的类型
public interface GirlRep extends JpaRepository<Girl,Integer> {
}

2.2Controller层

package com.hmblogs.backend.controller;


import com.hmblogs.backend.dao.GirlRep;
import com.hmblogs.backend.entity.Girl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
public class GirlController {

    @Autowired
    private GirlRep girlRep;

    /**
     * 查询所有女生列表
     * @return
     */
    @RequestMapping(value = "/girls",method = RequestMethod.GET)
    public List<Girl> getGirlList(){
        return girlRep.findAll();
    }

    /**
     * 添加一个女生
     * @param cupSize
     * @param age
     * @return
     */
    @RequestMapping(value = "/girls",method = RequestMethod.POST)
    public Girl addGirl(@RequestParam("cupSize") String cupSize,
                        @RequestParam("age") Integer age){
        Girl girl = new Girl();
        girl.setAge(age);
        girl.setCupSize(cupSize);
        return girlRep.save(girl);
    }

}

2.3entity层

package com.hmblogs.backend.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.Id;


@Entity
public class Girl {

    @Id
    @GeneratedValue
    private Integer id;
    private String cupSize;
    private Integer age;

    public Girl() {
    }

    public Integer getId() {
        return id;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getCupSize() {
        return cupSize;
    }

    public void setCupSize(String cupSize) {
        this.cupSize = cupSize;
    }
}

2.4启动类

package com.hmblogs.backend;

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

@SpringBootApplication
public class BackendApplication {

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

}

2.5配置文件

server:
  port: 8080
  context-path: /backend

girl:
  name: B
  age: 18
  content: content:${name},age:${age}

spring:
  profiles:
    active: prod
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/dbgirl?useUnicode=true&characterEncoding=utf8&characterSetResults=utf8
    username: root
    password: 123
  jpa:
    hibernate:
      ddl-auto: create
    show-sql: true

其中girl节点只是让我练习注解用的，可以不用管。

而

jpa:
hibernate:
ddl-auto: create

表示会自动创建表，如果事先已经建好表了，可以忽略不用。

2.6代码结构如下图所示

3、都准备好之后，启动，报错

参考源发行版17需要目标发行版17_java代码学习者的博客-CSDN博客

解决了，但是又报其它错了

参考【异常解决】java: 无法访问org.springframework.boot.SpringApplication的解决方案_IT技术分享网

降低了boot版本后，pom.xml文件如下

<?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>2.1.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.hmblogs</groupId>
    <artifactId>backend</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>backend</name>
    <description>backend</description>
    <properties>
        <java.version>8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

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

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

    </dependencies>

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

</project>

Girl.java要改成这样

package com.hmblogs.backend.entity;


import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class Girl {

    @Id
    @GeneratedValue
    private Integer id;
    private String cupSize;
    private Integer age;

    public Girl() {
    }

    public Integer getId() {
        return id;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getCupSize() {
        return cupSize;
    }

    public void setCupSize(String cupSize) {
        this.cupSize = cupSize;
    }
}

但是报错了