JpaRepository的关联查询和@Query查询

一 pom

<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>org.fkit</groupId>
     <artifactId>springdatajpaquerytest</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <packaging>jar</packaging>
     <name>springdatajpaquerytest</name>
     <url>http://maven.apache.org</url>
     <!-- spring-boot-starter-parent是Spring Boot的核心启动器，  包含了自动配置、日志和YAML等大量默认的配置，大大简化了我们的开发。
           引入之后相关的starter引入就不需要添加version配置， spring  boot会自动选择最合适的版本进行添加。 -->
     <parent>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-parent</artifactId>
           <version>2.0.0.RELEASE</version>
           <relativePath />
     </parent>
     <properties>
           <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
           <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
           <java.version>1.8</java.version>
     </properties>
     <dependencies>
           <!-- 添加spring-boot-starter-web模块依赖 -->
           <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
           </dependency>
           <!-- 添加spring-boot-starter-thymeleaf模块依赖 -->
           <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-thymeleaf</artifactId>
           </dependency>
           <!-- 添加MySQL依赖 -->
           <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
           </dependency>
           <!-- 添加Spring Data JPA依赖 -->
           <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
           </dependency>
           <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <scope>test</scope>
           </dependency>
     </dependencies>
</project>

二 启动类

package org.fkit.springdatajpaquerytest;

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


@SpringBootApplication
public class App
{
    public static void main( String[] args )
    {
        // SpringApplication 用于从main方法启动Spring应用的类。
        SpringApplication.run(App.class, args);
    }
}

三 配置文件

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spring.datasourc