通过spring-data-jpa进行复杂对象查询

2019-11-06 09:05:24

字体：大中小

来源：转载

供稿：网友

建立数据库表 person表

id	sex	name	country_id
1	男	张三	1
2	女	李四	1

country表

id	name
1	中国
2	美国

role表

id	name	person_id
1	教师	1
2	学生	2
3	司机	1

从表的内容可以看出person与role是一对多的关系，例如张三可以同时是教师与司机。person与country是多对一的关系，例如张三与李四都是中国人。

创建Person实体类

import javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.FetchType;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.ManyToOne;import javax.persistence.OneToMany;import javax.persistence.Table;import java.io.Serializable;import java.util.List;/** * 复杂对象测试实体 * person - country 多对一 * person - role 一对多 * Created by shiyufeng on 2017/2/14. */@Entity@Table(name = "person")public class Person implements Serializable { @Id PRivate String id; @Column private String name; @Column private String sex; /* * cascade：为级联操作，里面有级联保存，级联删除等，all为所有 * fetch：加载类型，有lazy和eager二种， * eager为急加载，意为立即加载，在类加载时就加载，lazy为慢加载，第一次调用的时候再加载，由于数据量太大，onetomany一般为lazy * mappedBy：这个为manytoone中的对象名，这个不要变哦.指向的是要关联的属性，而不是要关联的类 * Set<role>：这个类型有两种，一种为list另一种为set */ @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "person") private List<Role> roles; @ManyToOne @JoinColumn(name = "country_id") private Country country; public List<Role> getRoles() { return roles; } public void setRoles(List<Role> roles) { this.roles = roles; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public Country getCountry() { return country; } public void setCountry(Country country) { this.country = country; } @Override public String toString() { return "Person{" + "id='" + id + '/'' + ", name='" + name + '/'' + ", sex='" + sex + '/'' + '}'; }}

创建Role实体类

import javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.ManyToOne;import java.io.Serializable;@Entitypublic class Role implements Serializable { @Id private String id; @Column private String name; @ManyToOne(cascade = CascadeType.ALL) @JoinColumn(name = "person_id") private Person person; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Person getPerson() { return person; } public void setPerson(Person person) { this.person = person; } @Override public String toString() { return "Role{" + "id='" + id + '/'' + ", name='" + name + '/'' + '}'; }}

创建Country实体类

import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;/** * Created by shiyufeng on 2017/2/15. */@Entity@Table(name = "country")public class Country implements Serializable{ @Id private String id; @Column private String name; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "Country{" + "id='" + id + '/'' + ", name='" + name + '/'' + '}'; }}

创建PersonRepository数据库访问接口继承之前的BaseRepository通用Dao(BaseRepository中写好了基本的增删改查接口。也可以不继承，自己自定义接口)。

public interface PersonRepository extends BaseRepository<Person, String> { public Person findByName(String name);}

创建服务控制类ComplexEntityController

import cn.entity.Country;import cn.entity.Person;import cn.entity.Role;import cn.service.PersonRepository;import org.springframework.boot.autoconfigure.EnableAutoConfiguration;import org.springframework.transaction.annotation.EnableTransactionManagement;import org.springframework.transaction.annotation.Transactional;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;import javax.annotation.Resource;import java.util.ArrayList;import java.util.List;/** * 复杂对象测试用例 * Created by shiyufeng on 2017/2/14. */@Transactional // 事务@RestController@EnableAutoConfiguration@EnableTransactionManagement // 开启注解事务管理，等同于xml配置文件中的 <tx:annotation-driven />public class ComplexEntityController { @Resource private PersonRepository personRepository; /** * person - country 多对一 * person - role 一对多 * * @return */ @RequestMapping("/findPerson") public String findPerson() { Person person = personRepository.find(Person.class, "2"); System.out.println(person); System.out.println(person.getCountry()); List<Role> roles = person.getRoles(); for (Role role : roles) { System.out.println(role); } return "success!"; }}

启动服务，通过访问localhost:8080/findPerson即可得到person的信息。

上一篇：[Caffe]: 关于concat layer

下一篇：智慧交通指挥决策平台，让“城市大脑”尽收眼底