jpa多表查询可以使用构造器的方式进行多表查询，以下为多表查询的案例。
本案例中有A、B、C三个对象实体类，对象A、B通过属性imsi关联，对象B、C通过imsig关联；
还有一个Abc类，它是一个用来多表查询时构造集合的普通类。
以下为案例代码
A类
package com.ljq.entity;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
/**
* 对象A、B通过属性imsi关联
*
* @author jiqinlin
*
*/
@SuppressWarnings( " serial " )
@Entity
public class A implements Serializable {
@Id
@GeneratedValue
private Integer id;
@Column(nullable = false , length = 20 )
private String imsi;
@Column(nullable = false , length = 20 )
private String sipss;
public A() {
super ();
}
public A(String imsi, String sipss) {
super ();
this .imsi = imsi;
this .sipss = sipss;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this .id = id;
}
public String getImsi() {
return imsi;
}
public void setImsi(String imsi) {
this .imsi = imsi;
}
public String getSipss() {
return sipss;
}
public void setSipss(String sipss) {
this .sipss = sipss;
}
}
B类
package com.ljq.entity;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
@SuppressWarnings( " serial " )
@Entity
public class B implements Serializable {
@Id
@GeneratedValue
private Integer id;
@Column(nullable = false , length = 20 )
private String imsi;
@Column(nullable = false , length = 20 )
private String imsig;
@Column(nullable = false , length = 20 )
private String mdn;
public B() {
super ();
}
public B(String imsi, String imsig, String mdn) {
super ();
this .imsi = imsi;
this .imsig = imsig;
this .mdn = mdn;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this .id = id;
}
public String getImsi() {
return imsi;
}
public void setImsi(String imsi) {
this .imsi = imsi;
}
public String getImsig() {
return imsig;
}
public void setImsig(String imsig) {
this .imsig = imsig;
}
public String getMdn() {
return mdn;
}
public void setMdn(String mdn) {
this .mdn = mdn;
}
}
C类型
package com.ljq.entity;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
/**
* 对象B、C通过属性imsig关联
*
* @author jiqinlin
*
*/
@SuppressWarnings( " serial " )
@Entity
public class C implements Serializable {
@Id
@GeneratedValue
private Integer id;
@Column(nullable = false , length = 20 )
private String imsig;
@Column(nullable = false , length = 20 )
private String ki;
public C() {
super ();
}
public C(String imsig, String ki) {
super ();
this .imsig = imsig;
this .ki = ki;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this .id = id;
}
public String getImsig() {
return imsig;
}
public void setImsig(String imsig) {
this .imsig = imsig;
}
public String getKi() {
return ki;
}
public void setKi(String ki) {
this .ki = ki;
}
}
Abc类型
package com.ljq.entity;
import java.io.Serializable;
/**
* 多表查询时用来构造集合的实体类
*
* @author jiqinlin
*
*/
@SuppressWarnings( " serial " )
public class Abc implements Serializable {
/** 实体类主键 * */
private Integer id;
private String imsi;
private String imsig;
private String sipss;
private String mdn;
private String ki;
public Abc() {
}
public Abc(String imsi, String sipss, String mdn) {
this .imsi = imsi;
this .sipss = sipss;
this .mdn = mdn;
}
public Abc(String imsi, String imsig, String mdn, String ki) {
super ();
this .imsi = imsi;
this .imsig = imsig;
this .mdn = mdn;
this .ki = ki;
}
public Abc(String imsi, String imsig, String sipss, String mdn, String ki) {
super ();
this .imsi = imsi;
this .imsig = imsig;
this .sipss = sipss;
this .mdn = mdn;
this .ki = ki;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this .id = id;
}
public String getImsi() {
return imsi;
}
public void setImsi(String imsi) {
this .imsi = imsi;
}
public String getImsig() {
return imsig;
}
public void setImsig(String imsig) {
this .imsig = imsig;
}
public String getSipss() {
return sipss;
}
public void setSipss(String sipss) {
this .sipss = sipss;
}
public String getMdn() {
return mdn;
}
public void setMdn(String mdn) {
this .mdn = mdn;
}
public String getKi() {
return ki;
}
public void setKi(String ki) {
this .ki = ki;
}
}
MultiListQueryTest测试类
package junit.test;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import org.junit.Test;
import com.ljq.entity.A;
import com.ljq.entity.Abc;
import com.ljq.entity.B;
import com.ljq.entity.C;
/**
* 多表查询
*
* @author jiqinlin
*
*/
public class MultiListQueryTest {
@Test
public void add() throws Exception {
EntityManagerFactory factory = Persistence.createEntityManagerFactory( " ljq " );
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
em.persist( new A( " 41650a " , " abcefg1 " ));
em.persist( new A( " 41650b " , " abcefg2 " ));
em.persist( new A( " 41650c " , " abcefg3 " ));
em.persist( new C( " imsig_a " , " 12345a " ));
em.persist( new C( " imsig_b " , " 12345b " ));
em.persist( new C( " imsig_c " , " 12345c " ));
em.persist( new C( " imsig_e " , " 12345d " ));
em.persist( new B( " 41650a " , " imsig_a " , " 059188893381 " ));
em.persist( new B( " 41650b " , " imsig_b " , " 059188893382 " ));
em.persist( new B( " 41650e " , " imsig_c " , " 059188893383 " ));
em.persist( new B( " 41650aa " , " imsig_123 " , " 059188893384 " ));
em.persist( new B( " 41650cc " , " imsig_1 " , " 059188893385 " ));
em.getTransaction().commit();
em.close();
factory.close();
}
/**
* 多表查询对象A、B
*
* @throws Exception
*/
@Test
public void queryAB() throws Exception {
EntityManagerFactory factory = Persistence.createEntityManagerFactory( " ljq " );
EntityManager em = factory.createEntityManager();
List < Abc > abcs = em.createQuery( " select new com.ljq.entity.Abc(a.imsi, a.sipss, b.mdn) " +
" from A a, B b where a.imsi=b.imsi " ).getResultList();
for (Abc abc : abcs){
System.out.println( " imsi: " + abc.getImsi());
System.out.println( " sipss: " + abc.getSipss());
System.out.println( " mdn: " + abc.getMdn());
System.out.println( " ======== " );
}
em.close();
factory.close();
}
/**
* 多表查询对象B、C
*
* @throws Exception
*/
@Test
public void queryBC() throws Exception {
EntityManagerFactory factory = Persistence.createEntityManagerFactory( " ljq " );
EntityManager em = factory.createEntityManager();
List < Abc > abcs = em.createQuery( " select new com.ljq.entity.Abc(b.imsi, b.imsig, b.mdn, c.ki) " +
" from B b, C c where b.imsig=c.imsig " ).getResultList();
for (Abc abc : abcs){
System.out.println( " imsi: " + abc.getImsi());
System.out.println( " imsig: " + abc.getImsig());
System.out.println( " mdn: " + abc.getMdn());
System.out.println( " ki: " + abc.getKi());
System.out.println( " ======= " );
}
em.close();
factory.close();
}
/**
* 多表查询对象A、B、C
*
* @throws Exception
*/
@Test
public void queryABC() throws Exception {
EntityManagerFactory factory = Persistence.createEntityManagerFactory( " ljq " );
EntityManager em = factory.createEntityManager();
List < Abc > abcs = em.createQuery( " select new com.ljq.entity.Abc(b.imsi, b.imsig, a.sipss, b.mdn, c.ki) " +
" from A a, B b, C c where a.imsi=b.imsi and b.imsig=c.imsig " ).getResultList();
for (Abc abc : abcs){
System.out.println( " imsi: " + abc.getImsi());
System.out.println( " imsig: " + abc.getImsig());
System.out.println( " sipss: " + abc.getSipss());
System.out.println( " mdn: " + abc.getMdn());
System.out.println( " ki: " + abc.getKi());
System.out.println( " ======= " );
}
em.close();
factory.close();
}
@Test
public void test() throws Exception {
Persistence.createEntityManagerFactory( " ljq " );
}
}
原创文章，作者：奋斗，如若转载，请注明出处：https://blog.ytso.com/16112.html