SpringBoot整合JPA 完成多对多关联添加查询

SpringBoot整合JPA 完成关联查询

以专家和事件为例

sql语句

CREATE TABLE `expert` ( `id` int(11) NOT NULL AUTO_INCREMENT, `expertName` varchar(255) DEFAULT NULL COMMENT '专家名称', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8; CREATE TABLE `event` ( `id` int(11) NOT NULL AUTO_INCREMENT, `eventName` varchar(255) DEFAULT NULL COMMENT '事件名称', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

pom依赖

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>com.vladmihalcea</groupId> <artifactId>hibernate-types-5</artifactId> <version>2.4.2</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.1.5</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <optional>true</optional> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> <exclusions> <exclusion> <groupId>org.junit.vintage</groupId> <artifactId>junit-vintage-engine</artifactId> </exclusion> </exclusions> </dependency>

application文件

server: port: 9999 spring: application: name: springboot-jpa datasource: type: com.alibaba.druid.pool.DruidDataSource url: jdbc:mysql://localhost:3306/xxxx?useUnicode=true&characterEncoding=utf-8&useSSL=false&autoReconect=true&serverTimezone=GMT%2b8 username: xxxx password: xxxx driver-class-name: com.mysql.jdbc.Driver filters: stat maxActive: 50 initialSize: 0 maxWait: 60000 minIdle: 1 timeBetweenEvictionRunsMillis: 60000 minEvictableIdleTimeMillis: 300000 validationQuery: select 1 from dual testWhileIdle: true testOnBorrow: false testOnReturn: false poolPreparedStatements: true maxOpenPreparedStatements: 20 removeAbandoned: true removeAbandonedTimeout: 180 jpa: show-sql: true hibernate: naming: physical-strategy: org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl ddl-auto: update properties: hibernate: format_sql: true show_sql: true current_session_context_class: org.springframework.orm.hibernate5.SpringSessionContext dialect: org.hibernate.dialect.MySQL5Dialect

实体类

@Entity @Table ( name ="event" ) @DynamicInsert(true) @DynamicUpdate(true) public class Event implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "id" ) private Integer id; /**事件名称*/ @Column(name = "eventName" ) private String eventName; //cascade = CascadeType.PERSIST 代表级联保存 @ManyToMany(cascade = CascadeType.PERSIST) /** * name : 中间表名称 * joinColumns : 当前表中主键关联字段 * JoinColumn 字段名 referencedColumnName 引用实体表字段名 * inverseJoinColumns ： 当前表中另一个关联字段 * */ @JoinTable(name = "expert_event",joinColumns = @JoinColumn(name = "expert_id",referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "event_id",referencedColumnName = "id")) private Set<Expert> expertSet = new HashSet<>(); get set ... @Entity @Table ( name ="expert" ) @DynamicInsert(true) @DynamicUpdate(true) public class Expert implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "id" ) private Integer id; /**专家名称*/ @Column(name = "expertName" ) private String expertName; //mappedBy 关联的另一侧字段名称 @ManyToMany(mappedBy = "expertSet") private Set<Event> eventSet = new HashSet<>(); get set ... }

dao层直接继承JpaRepository即可

public interface EventRepository extends JpaRepository<Event,Integer> { }

编写测试类

@RunWith(SpringJUnit4ClassRunner.class) @SpringBootTest(classes = TmpApplication.class) public class JpaTest { @Autowired private EventRepository eventRepository; @Test public void save(){ //创建事件 Event event = new Event(); event.setEventName("消防事件"); //创建专家 Expert expert = new Expert(); expert.setExpertName("成博士"); Expert expert1 = new Expert(); expert1.setExpertName("赵博士"); //关联 event.getExpertSet().add(expert); event.getExpertSet().add(expert1); expert.getEventSet().add(event); expert1.getEventSet().add(event); this.eventRepository.save(event); } @Test public void select(){ //查询事件 Event event1 = eventRepository.findById(2).get(); System.out.println(event1.getEventName()); //在测试类中，对象下面的集合取出会报一个session错误 //是因为jpa默认是懒加载，改为立即加载或者在controller测试即可 Set<Expert> expertSet = event1.getExpertSet(); for (Expert expert : expertSet) { System.out.println(expert.getExpertName()); } }

至此一个JPA多对多关联添加查询就完成了。有什么问题欢迎评论区指出