Spring JPA 简单配置使用

JPA 常用配置：

# JPA (JpaBaseConfiguration, HibernateJpaAutoConfiguration)
spring.data.jpa.repositories.bootstrap-mode=default # Bootstrap mode for JPA repositories.
spring.data.jpa.repositories.enabled=true # Whether to enable JPA repositories.
spring.jpa.database= # Target database to operate on, auto-detected by default. Can be alternatively set using the "databasePlatform" property.
spring.jpa.database-platform= # Name of the target database to operate on, auto-detected by default. Can be alternatively set using the "Database" enum.
spring.jpa.generate-ddl=false # Whether to initialize the schema on startup.
spring.jpa.hibernate.ddl-auto= # DDL mode. This is actually a shortcut for the "hibernate.hbm2ddl.auto" property. Defaults to "create-drop" when using an embedded database and no schema manager was detected. Otherwise, defaults to "none".
spring.jpa.hibernate.naming.implicit-strategy= # Fully qualified name of the implicit naming strategy.
spring.jpa.hibernate.naming.physical-strategy= # Fully qualified name of the physical naming strategy.
spring.jpa.hibernate.use-new-id-generator-mappings= # Whether to use Hibernate's newer IdentifierGenerator for AUTO, TABLE and SEQUENCE.
spring.jpa.mapping-resources= # Mapping resources (equivalent to "mapping-file" entries in persistence.xml).
spring.jpa.open-in-view=true # Register OpenEntityManagerInViewInterceptor. Binds a JPA EntityManager to the thread for the entire processing of the request.
spring.jpa.properties.*= # Additional native properties to set on the JPA provider.
spring.jpa.show-sql=false # Whether to enable logging of SQL statements.

DataSource 配置：

# DATASOURCE (DataSourceAutoConfiguration & DataSourceProperties)
spring.datasource.continue-on-error=false # Whether to stop if an error occurs while initializing the database.
spring.datasource.data= # Data (DML) script resource references.
spring.datasource.data-username= # Username of the database to execute DML scripts (if different).
spring.datasource.data-password= # Password of the database to execute DML scripts (if different).
spring.datasource.dbcp2.*= # Commons DBCP2 specific settings
spring.datasource.driver-class-name= # Fully qualified name of the JDBC driver. Auto-detected based on the URL by default.
spring.datasource.generate-unique-name=false # Whether to generate a random datasource name.
spring.datasource.hikari.*= # Hikari specific settings
spring.datasource.initialization-mode=embedded # Initialize the datasource with available DDL and DML scripts.
spring.datasource.jmx-enabled=false # Whether to enable JMX support (if provided by the underlying pool).
spring.datasource.jndi-name= # JNDI location of the datasource. Class, url, username & password are ignored when set.
spring.datasource.name= # Name of the datasource. Default to "testdb" when using an embedded database.
spring.datasource.password= # Login password of the database.
spring.datasource.platform=all # Platform to use in the DDL or DML scripts (such as schema-${platform}.sql or data-${platform}.sql).
spring.datasource.schema= # Schema (DDL) script resource references.
spring.datasource.schema-username= # Username of the database to execute DDL scripts (if different).
spring.datasource.schema-password= # Password of the database to execute DDL scripts (if different).
spring.datasource.separator=; # Statement separator in SQL initialization scripts.
spring.datasource.sql-script-encoding= # SQL scripts encoding.
spring.datasource.tomcat.*= # Tomcat datasource specific settings
spring.datasource.type= # Fully qualified name of the connection pool implementation to use. By default, it is auto-detected from the classpath.
spring.datasource.url= # JDBC URL of the database.
spring.datasource.username= # Login username of the database.
spring.datasource.xa.data-source-class-name= # XA datasource fully qualified name.
spring.datasource.xa.properties= # Properties to pass to the XA data source.

目录结构

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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.springtest</groupId>
    <artifactId>myspringtest1</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.5.RELEASE</version>
    </parent>
    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
            <version>2.1.5.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.6</version>
        </dependency>

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

</project>

2. logback-spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- 日志级别从低到高分为TRACE < DEBUG < INFO < WARN < ERROR < FATAL，如果设置为WARN，则低于WARN的信息都不会输出 -->
<!-- scan:当此属性设置为true时，配置文档如果发生改变，将会被重新加载，默认值为true -->
<!-- scanPeriod:设置监测配置文档是否有修改的时间间隔，如果没有给出时间单位，默认单位是毫秒。
                 当scan为true时，此属性生效。默认的时间间隔为1分钟。 -->
<!-- debug:当此属性设置为true时，将打印出logback内部日志信息，实时查看logback运行状态。默认值为false。 -->
<configuration  scan="true" scanPeriod="10 seconds">
    <contextName>logback</contextName>

    <springProfile name="dev">
        <property name="log.path" value="/Users/guoxiwang/software/idea/log/dev" />
    </springProfile>
    <springProfile name="prd">
        <property name="log.path" value="/Users/guoxiwang/software/idea/log/prd" />
    </springProfile>

    <!-- name的值是变量的名称，value的值时变量定义的值。通过定义的值会被插入到logger上下文中。定义后，可以使“${}”来使用变量。 -->
<!--    <property name="log.path" value="/Users/guoxiwang/software/idea/log" />-->

    <!--0. 日志格式和颜色渲染 -->
    <!-- 彩色日志依赖的渲染类 -->
    <conversionRule conversionWord="clr" converterClass="org.springframework.boot.logging.logback.ColorConverter" />
    <conversionRule conversionWord="wex" converterClass="org.springframework.boot.logging.logback.WhitespaceThrowableProxyConverter" />
    <conversionRule conversionWord="wEx" converterClass="org.springframework.boot.logging.logback.ExtendedWhitespaceThrowableProxyConverter" />
    <!-- 彩色日志格式 -->
    <property name="CONSOLE_LOG_PATTERN" value="${CONSOLE_LOG_PATTERN:-%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %clr(${LOG_LEVEL_PATTERN:-%5p}) %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}}"/>

    <!--1. 输出到控制台-->
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <!--此日志appender是为开发使用，只配置最底级别，控制台输出的日志级别是大于或等于此级别的日志信息-->
        <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
            <level>debug</level>
        </filter>
        <encoder>
            <Pattern>${CONSOLE_LOG_PATTERN}</Pattern>
            <!-- 设置字符集 -->
            <charset>UTF-8</charset>
        </encoder>
    </appender>

    <!--2. 输出到文档-->
    <!-- 2.1 level为 DEBUG 日志，时间滚动输出  -->
    <appender name="DEBUG_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <!-- 正在记录的日志文档的路径及文档名 -->
        <file>${log.path}/web_debug.log</file>
        <!--日志文档输出格式-->
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
            <charset>UTF-8</charset> <!-- 设置字符集 -->
        </encoder>
        <!-- 日志记录器的滚动策略，按日期，按大小记录 -->
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <!-- 日志归档 -->
            <fileNamePattern>${log.path}/web-debug-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>1MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
            <!--日志文档保留天数-->
            <maxHistory>15</maxHistory>
        </rollingPolicy>
        <!-- 此日志文档只记录debug级别的 -->
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>debug</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
    </appender>

    <!-- 2.2 level为 INFO 日志，时间滚动输出  -->
    <appender name="INFO_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <!-- 正在记录的日志文档的路径及文档名 -->
        <file>${log.path}/web_info.log</file>
        <!--日志文档输出格式-->
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
            <charset>UTF-8</charset>
        </encoder>
        <!-- 日志记录器的滚动策略，按日期，按大小记录 -->
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <!-- 每天日志归档路径以及格式 -->
            <fileNamePattern>${log.path}/web-info-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>100MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
            <!--日志文档保留天数-->
            <maxHistory>15</maxHistory>
        </rollingPolicy>
        <!-- 此日志文档只记录info级别的 -->
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>info</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
    </appender>

    <!-- 2.3 level为 WARN 日志，时间滚动输出  -->
    <appender name="WARN_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <!-- 正在记录的日志文档的路径及文档名 -->
        <file>${log.path}/web_warn.log</file>
        <!--日志文档输出格式-->
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
            <charset>UTF-8</charset> <!-- 此处设置字符集 -->
        </encoder>
        <!-- 日志记录器的滚动策略，按日期，按大小记录 -->
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>${log.path}/web-warn-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>1MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
            <!--日志文档保留天数-->
            <maxHistory>15</maxHistory>
        </rollingPolicy>
        <!-- 此日志文档只记录warn级别的 -->
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>warn</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
    </appender>

    <!-- 2.4 level为 ERROR 日志，时间滚动输出  -->
    <appender name="ERROR_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <!-- 正在记录的日志文档的路径及文档名 -->
        <file>${log.path}/web_error.log</file>
        <!--日志文档输出格式-->
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
            <charset>UTF-8</charset> <!-- 此处设置字符集 -->
        </encoder>
        <!-- 日志记录器的滚动策略，按日期，按大小记录 -->
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>${log.path}/web-error-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>1MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
            <!--日志文档保留天数-->
            <maxHistory>15</maxHistory>
        </rollingPolicy>
        <!-- 此日志文档只记录ERROR级别的 -->
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>ERROR</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
    </appender>

    <!--
        <logger>用来设置某一个包或者具体的某一个类的日志打印级别、
        以及指定<appender>。<logger>仅有一个name属性，
        一个可选的level和一个可选的addtivity属性。
        name:用来指定受此logger约束的某一个包或者具体的某一个类。
        level:用来设置打印级别，大小写无关：TRACE, DEBUG, INFO, WARN, ERROR, ALL 和 OFF，
              还有一个特俗值INHERITED或者同义词NULL，代表强制执行上级的级别。
              如果未设置此属性，那么当前logger将会继承上级的级别。
        addtivity:是否向上级logger传递打印信息。默认是true。
        <logger name="org.springframework.web" level="info"/>
        <logger name="org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor" level="INFO"/>
    -->

    <!--
        使用mybatis的时候，sql语句是debug下才会打印，而这里我们只配置了info，所以想要查看sql语句的话，有以下两种操作：
        第一种把<root level="info">改成<root level="DEBUG">这样就会打印sql，不过这样日志那边会出现很多其他消息
        第二种就是单独给dao下目录配置debug模式，代码如下，这样配置sql语句会打印，其他还是正常info级别：
        【logging.level.org.mybatis=debug logging.level.dao=debug】
     -->

    <!--
        root节点是必选节点，用来指定最基础的日志输出级别，只有一个level属性
        level:用来设置打印级别，大小写无关：TRACE, DEBUG, INFO, WARN, ERROR, ALL 和 OFF，
        不能设置为INHERITED或者同义词NULL。默认是DEBUG
        可以包含零个或多个元素，标识这个appender将会添加到这个logger。
    -->

    <!-- 4. 最终的策略 -->
    <!-- 4.1 开发环境:打印控制台-->
    <springProfile name="dev">
        <logger name="com.springtest.mytest1" level="debug"/>
    </springProfile>

    <root level="info">
        <appender-ref ref="CONSOLE" />
        <appender-ref ref="DEBUG_FILE" />
        <appender-ref ref="INFO_FILE" />
        <appender-ref ref="WARN_FILE" />
        <appender-ref ref="ERROR_FILE" />
    </root>

    <!-- 4.2 生产环境:输出到文档
    <springProfile name="pro">
        <root level="info">
            <appender-ref ref="CONSOLE" />
            <appender-ref ref="DEBUG_FILE" />
            <appender-ref ref="INFO_FILE" />
            <appender-ref ref="ERROR_FILE" />
            <appender-ref ref="WARN_FILE" />
        </root>
    </springProfile> -->
</configuration>

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/student?useUnicode=true&characterEncoding=utf-8
    username: root
    password: 12345678
  jpa:
    show-sql: true
    generate-ddl: true
    hibernate:
      ddl-auto: update
server:
  port: 8070

　　

3. RestController

package com.springtest.mytest1.controller;

import com.springtest.mytest1.entity.CustomUser;
import com.springtest.mytest1.model.User;
import com.springtest.mytest1.repo.CustomUserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import java.util.List;

@org.springframework.web.bind.annotation.RestController
@RequestMapping(path = "/test")
public class RestController {

    @Autowired
    CustomUserRepository customUserRepository;

    @RequestMapping(path = "/get",method = RequestMethod.GET)
    public CustomUser getUserName(){

        CustomUser data=customUserRepository.findOneByName("guoxw");

        return data;

    }

    @RequestMapping(path = "/getStr" ,method = RequestMethod.GET)
    public String getString(){

        return "111";
    }

    @RequestMapping(path = "/getAll")
    public List<CustomUser>getAll(){
        return customUserRepository.findAll();
    }

    /**
     *
     * @param name 简单的查询  finByName
     *
     * @return
     */
    @RequestMapping(path = "/findByName")
    public CustomUser findByName(@RequestParam  String name){

        return  customUserRepository.findByName(name);

    }

    /**
     *
     * @param user
     * @return
     */
    @RequestMapping(path = "/user", method = RequestMethod.POST)
    public User TestUserCreate(@RequestBody User user) {
        // logger.debug("Request body is: {}", user);

        return user;
    }

    @RequestMapping(path = "/add",method = RequestMethod.POST)
    public void  CreateCustomUer(@RequestBody CustomUser user){

        customUserRepository.save(user);
        return;

    }

    @RequestMapping(path = "/findByUserId",method = RequestMethod.POST)
    public CustomUser findByUserId(@RequestParam Long id){

       // return  customUserRepository.findByUserId(id);

        return null;
    }

    @RequestMapping(path = "/update",method = RequestMethod.POST)
    public void updateById(@RequestParam  String  name){

          customUserRepository.updateByName(name);
          return;
    }

    @RequestMapping(path = "/del",method = RequestMethod.POST)
    public void  delById(@RequestParam long id){

       //customUserRepository.delByUserId(id);

    }

}

4.CustomUser

package com.springtest.mytest1.entity;
import javax.persistence.*;
import java.io.Serializable;

@Entity(name = "custom_user")
public class CustomUser implements Serializable {

    @Id
    @GeneratedValue (strategy = GenerationType.IDENTITY)
    @Column(name = "custom_id",unique = true)
    private Long id;

    @Column(name = "custom_name")
    private String name;

    @Column(name = "custom_age")
    private int age;

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

　　

5. CustomRepository　

package com.springtest.mytest1.repo;

import com.springtest.mytest1.entity.CustomUser;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

@Repository
public interface CustomUserRepository extends JpaRepository<CustomUser,Long> {

     CustomUser findOneByName(String name);

    /***
     *
     * @param name   CustomUser 里面的字段
     *
     * @return
     */
     CustomUser findByName(String name);

//     @Query("select u from custom_user  u where u.age= ? 18")
//     CustomUser findByUserId(Long id);
//
//     @Transactional
//     @Modifying
//     @Query("delete from custom_user u where id=? 18 ")
//     void  delByUserId(Long id);

     @Transactional(timeout = 10)
     @Modifying
     @Query("update custom_user  u set u.name='guoxw_3'  where u.name='guoxw_2' ")  // 在这里的 custom_user 使用的是 Entity name里面的属性，即是数据库表明，但是 u.name这里的name是实体类的属性，
　　//   并不是数据库里面的字段名称

　　void updateByName(String name); } 

　

  /***
     *
     * @param name   CustomUser 里面的字段
     *
     * @return
     */
     CustomUser findByName(String name);

     @Query("select u from custom_user  u where u.id=1")
     CustomUser findByUserId(@Param("ID") Long ID);

　　

　

　

　

JPA 使用

http://www.ityouknow.com/springboot/2016/08/20/spring-boot-jpa.html

code: idea_code的副本

JPA

占位符 ?1 表示传入的第一个参数
nativeQuery = true 表示原生sql 语句
不加 nativeQuery = true则sql 语句中是entity 的属性字段
不加 nativeQuery =true JPA 不能使用insert 语句

public interface CustomRepository extends JpaRepository<CustomUser,Long> {

    //  占位符 ?1 表示传入的第一个参数
    //  nativeQuery = true 表示原生sql 语句
    //  不加 nativeQuery = true则sql 语句中是entity 的属性字段
    //  不加 nativeQuery =true JPA 不能使用insert 语句
    @Modifying
    @Query(value = "select   user from  CustomUser  user where user.id >?1 and user.age>?2")
    List<CustomUser> findCustomById(int user_id, int age);

    @Modifying
    @Transactional
    @Query(value = "insert custom_user (custom_name,custom_age) values(?1,?2) " ,nativeQuery = true)
    void  addCustomUser(String name,int age);

    @Modifying
    @Transactional(noRollbackFor = Exception.class)
    @Query(value = "delete  from  custom_user where custom_id=?1", nativeQuery = true)
    void delUser(int id);

    @Modifying
    @Transactional(noRollbackFor = Exception.class)
    @Query(value = "update  custom_user set custom_name=?2 where  custom_id=?1",nativeQuery = true)
    void update(int id ,String name);

    @Modifying
    @Transactional
    @Query(value = "select   * from  custom_user ",nativeQuery = true)
    List<Map<String,Object>> findAllUser();

}

@Entity
@Table(name = "custom_user")   // 生成的数据表的名称是 custom_user
public class CustomUser {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "custom_id")
    public  int id;

    @Column(name = "custom_name")
    public String name;

    @Column(name ="custom_age")
    public  int age;

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

联合查询

<?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>2.1.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.gail</groupId>
    <artifactId>jpa</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>jpa</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-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.20</version>
        </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>
        </dependency>
    </dependencies>

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

</project>

　　

数据表 course

@Entity
@Table(name = "course")
public class Course {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    public  int id;

    @Column(name = "user_grade")
    public int userGrade;

    @Column(name = "user_id")
    public int userId;

    @Column(name = "grade_name")
    public  String gradeName;
}

　

数据表 student

@Entity
@Table(name = "student")
public class Student {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    public int id;

    @Column(name = "user_id")
    public int userId;

    @Column(name = "user_name")
    public String userName;

    @Column(name = "user_age")
    public int userAge;
}　

实体类：StudentCourse

public class StudentCourse {

    private int userId;

    private String userName;

    private int userAge;

    private String gradeName;

    private int userGrade;
}

　　

　

JPA 多表联合查询 返回List<Map<String,Object>>对象

@Repository
public interface  AccountRepository  extends JpaRepository<Course,Integer> {

    @Query(value = "select s.user_id,s.user_name,s.user_age,c.grade_name,c.user_grade " +
            "from course  c left join  student s  on (c.user_id=s.user_id && s.user_id=?1)", nativeQuery = true)
    List<Map<String,Object>> getStudentCourse(int userId);

}

　　

　

Jpa 联合查询，自定义 JpaRepository  返回List<Class>对象

@Repository
public class StudentCourseRepo {

    @Autowired
    private NamedParameterJdbcTemplate template;

    private static final String queryString = "select s.user_id,s.user_name,s.user_age,c.grade_name,c.user_grade " +
            "from course  c left join  student s  on (c.user_id=s.user_id && s.user_id= :userId)";

    public List<StudentCourse> queryStudentCource(int userId) {
        MapSqlParameterSource mapSqlParameterSource = new MapSqlParameterSource().addValue("userId", userId);

        return template.query(queryString, mapSqlParameterSource, (ResultSet rs, int row) -> {
            StudentCourse sc = new StudentCourse();
            sc.setUserId(rs.getInt("user_id"));
            sc.setGradeName(rs.getString("grade_name"));
            return sc;
        });
    }
}