SpringBoot集成JPA

在SpringBoot中，通过Spring Data JPA 和 Spring Data Rest可以快速构建出一个RESTFul应用。

关于Spring Data JPA：JPA是一种规范，而Spring Data JPA可以有效简化关系型数据库访问代码。

关于Spring Data：Spring Data是Spring的一个子项目，致力于简化数据库访问。

JPA规范：

JPA中有种定义，将Java对象【POJO】映射到数据库。

@Entity（name=“t_book”）

表明该类为一个实体类，它默认对应数据库中的表名是t_book，在项目启动时会根据该类自动生成一张表。

【如果不配置name，默认表名为类名】

@Id

表示该属性是一个主键，@GeneratedValue(strategy = GenerationType.IDENTITY)表示主键自动生成，strategy表示主键生成策略。

创建工程

• 导入pom依赖

  <?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>org.sang</groupId>
  	<artifactId>jparestful</artifactId>
  	<version>0.0.1-SNAPSHOT</version>
  	<packaging>jar</packaging>
  
  	<name>jparestful</name>
  	<description>Demo project for Spring Boot</description>
  
  	<parent>
  		<groupId>org.springframework.boot</groupId>
  		<artifactId>spring-boot-starter-parent</artifactId>
  		<version>2.0.3.RELEASE</version>
  		<relativePath/> <!-- lookup parent from repository -->
  	</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>
  		<dependency>
  			<groupId>org.springframework.boot</groupId>
  			<artifactId>spring-boot-starter-data-jpa</artifactId>
  		</dependency>
  		<dependency>
  			<groupId>org.springframework.boot</groupId>
  			<artifactId>spring-boot-starter-data-rest</artifactId>
  		</dependency>
  		<dependency>
  			<groupId>com.alibaba</groupId>
  			<artifactId>druid</artifactId>
  			<version>1.1.9</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>
  
  

• 配置数据库连接

  spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
  spring.datasource.username=noneplus
  spring.datasource.password=Noneplus564925080!
  spring.datasource.url=jdbc:mysql://47.103.6.247:3306/restful-jpa?serverTimezone=UTC
  spring.jpa.hibernate.ddl-auto=update
  spring.jpa.database=mysql
  spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL57Dialect
  spring.jpa.show-sql=true
  
  ##每页默认记录数，缺省值为20
  #spring.data.rest.default-page-size=2
  ##分页查询页码参数名，缺省值为page
  #spring.data.rest.page-param-name=page
  ##分页查询记录数参数名，缺省值为size
  #spring.data.rest.limit-param-name=size
  ##分页查询排序参数名，缺省值为sort
  #spring.data.rest.sort-param-name=sort
  ##base-path表示给所有请求路径都加上前缀
  #spring.data.rest.base-path=/api
  ##添加成功时是否返回添加内容
  #spring.data.rest.return-body-on-create=true
  ##更新成功时是否返回更新内容
  #spring.data.rest.return-body-on-update=true
  

• 创建实体类

  @Entity(name = "t_book")
  public class Book {
      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      private Integer id;
      private String name;
      private String author;
      //省略getter/setter
  
      @Override
      public String toString() {
          return "Book{" +
                  "id=" + id +
                  ", name='" + name + '\'' +
                  ", author='" + author + '\'' +
                  '}';
      }
  
      public Integer getId() {
          return id;
      }
  
      public void setId(Integer id) {
          this.id = id;
      }
  
      public String getName() {
          return name;
      }
  
      public void setName(String name) {
          this.name = name;
      }
  
      public String getAuthor() {
          return author;
      }
  
      public void setAuthor(String author) {
          this.author = author;
      }
  }
  
  

• 创建BookRepository

  public interface BookRepository extends JpaRepository<Book, Integer> {
  
  }
  
  

• JpaRepository

  //
  // Source code recreated from a .class file by IntelliJ IDEA
  // (powered by Fernflower decompiler)
  //
  
  package org.springframework.data.jpa.repository;
  
  import java.util.List;
  import org.springframework.data.domain.Example;
  import org.springframework.data.domain.Sort;
  import org.springframework.data.repository.NoRepositoryBean;
  import org.springframework.data.repository.PagingAndSortingRepository;
  import org.springframework.data.repository.query.QueryByExampleExecutor;
  
  @NoRepositoryBean
  public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> {
      List<T> findAll();
  
      List<T> findAll(Sort var1);
  
      List<T> findAllById(Iterable<ID> var1);
  
      <S extends T> List<S> saveAll(Iterable<S> var1);
  
      void flush();
  
      <S extends T> S saveAndFlush(S var1);
  
      void deleteInBatch(Iterable<T> var1);
  
      void deleteAllInBatch();
  
      T getOne(ID var1);
  
      <S extends T> List<S> findAll(Example<S> var1);
  
      <S extends T> List<S> findAll(Example<S> var1, Sort var2);
  }
  
  

测试

【在进行这个节点测试之前，需要把代码的其他部分注释掉，之后会有一些自定义的功能】

在数据库添加几条测试数据

打开Postman，输入http://localhost:8080/books

【默认请求路径都是实体类名小写加s】

按照id查询

自定义请求路径

/**
 * 默认请求路径都是实体类名加s
 *
 * 自定义请求类名：
 * @RepositoryRestResource (path = "bs",collectionResourceRel = "bs",itemResourceRel = "b")
 * path属性指用bs替代原先的books，collectionResourceRel表示将返回的json集合中的book集合改为bs，
 * itemResourceRel表示将单个book的key改为b
 */
@RepositoryRestResource(path = "bs",collectionResourceRel = "bs",itemResourceRel = "b")
public interface BookRepository extends JpaRepository<Book, Integer> {

访问:http://localhost:8080/bs

自定义查询方法

     /**@RestResource注解定义：默认请求路径就是方法名，path可自定义路径
     * http://localhost:8080/bs/search/author?author=余华
     * http://localhost:8080/bs/search/name?name=白夜行
     * @param author
     * @return
     */
    @RestResource(path = "author",rel = "author")
    List<Book> findByAuthorContains(@Param("author") String author);
    @RestResource(path = "name",rel = "name")
    Book findByNameEquals(@Param("name") String name);

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