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JPA Native Query Support
JPA allow us to execute native SQL queries, instead of using JPQL. This is advantageous in the following scenarios.
When you're migrating a JDBC application to JPA on a strict deadline, and you don't have time to translate your existing SQL selects to JPQL.
Database developers can write fine-tuned queries, sometimes this cannot be done through JPQL, and in such cases we can use SQL queries in JPA.
We can make use of certain functions and support given in the SQL of the database.
How to execute native SQL queries form JPA
The EntityManager has the below two factory methods suitable for creating SQL queries, by passing a string SQL to these methods we can get the Query object.
public Query createNativeQuery(String sqlString, Class resultClass); public Query createNativeQuery(String sqlString, String resultSetMapping); |
These methods return persistent instances of entity class, at a minimum, SQL must select the class' primary key columns, discriminator column (if mapped), and version column (also if mapped).
EntityManagerFactory emf = Persistence.createEntityManagerFactory("StudentPU"); EntityManager em = emf.createEntityManager(); em.getTransaction().begin(); Query query = em.createNativeQuery("SELECT * FROM STUDENT", Student.class); List<Student> results = (List<Student>)query.getResultList(); |
We can use both Named parameters and Positional parameters in SQL as below:
Query query = em.createNativeQuery("SELECT * FROM STUDENT WHERE sname = :studentName", Student.class); query.setParameter("studentName", "Manu Manjunatha"); Query query = em.createNativeQuery("SELECT * FROM STUDENT WHERE sname = ?1", Student.class); query.setParameter(1, "Manu Manjunatha"); |
JPA Native Query Example
Database script (MySQL)
CREATE TABLE ADDRESS( AID INT(5) PRIMARY KEY AUTO_INCREMENT, CITY VARCHAR(30), ZIPCODE VARCHAR(30) );
CREATE TABLE STUDENT( SID INT(5) PRIMARY KEY AUTO_INCREMENT, SNAME VARCHAR(30), AID INT(5), CONSTRAINT FOREIGN KEY (AID) REFERENCES ADDRESS (AID) );
INSERT INTO ADDRESS(AID,CITY,ZIPCODE) VALUES (1,'Bangalore', '560010');
INSERT INTO STUDENT(SID,SNAME,AID) VALUES (1,'Manu Manjunatha', 1); INSERT INTO STUDENT(SID,SNAME,AID) VALUES (2,'Advith Tyagraj', 1); INSERT INTO STUDENT(SID,SNAME,AID) VALUES (3,'Likitha', 1); INSERT INTO STUDENT(SID,SNAME,AID) VALUES (4,'Tyagraj', 1); |
pom.xml
<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.java4coding</groupId> <artifactId>JPA_NativeQuerySupport</artifactId> <packaging>jar</packaging> <version>1.0-SNAPSHOT</version> <name>JPA_NativeQuerySupport</name> <url>https://maven.apache.org</url> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> <dependency> <groupId>org.eclipse.persistence</groupId> <artifactId>javax.persistence</artifactId> <version>2.0.0</version> </dependency>
<dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>4.2.8.Final</version> </dependency>
<dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.11</version> </dependency> </dependencies> </project>
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persistence.xml
<?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="https://java.sun.com/xml/ns/persistence" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://java.sun.com/xml/ns/persistence https://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" version="2.0">
<persistence-unit name="StudentPU"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <properties> <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/study" /> <property name="hibernate.connection.driver_class" value="com.mysql.cj.jdbc.Driver" /> <property name="hibernate.connection.username" value="root" /> <property name="hibernate.connection.password" value="root" /> <property name="hibernate.archive.autodetection" value="class" /> <property name="hibernate.show_sql" value="true" /> <property name="hibernate.format_sql" value="true" /> <property name="hbm2ddl.auto" value="update" /> </properties> </persistence-unit> </persistence> |
Address.java
package com.java4coding;
import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.Table;
@Entity @Table(name = "ADDRESS") public class Address {
@Id private int aid;
private String city;
private String zipcode;
public int getAid() { return aid; } public void setAid(int aid) { this.aid = aid; } public String getCity() { return city; } public void setCity(String city) { this.city = city; } public String getZipcode() { return zipcode; } public void setZipcode(String zipcode) { this.zipcode = zipcode; } } |
Student.java
package com.java4coding;
import javax.persistence.CascadeType; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table;
@Entity @Table(name = "STUDENT") public class Student {
@Id @GeneratedValue(strategy = GenerationType.AUTO) private int sid;
private String sname;
@ManyToOne(cascade = CascadeType.ALL) @JoinColumn(name= "AID") private Address address;
public int getSid() { return sid; } public void setSid(int sid) { this.sid = sid; } public String getSname() { return sname; } public void setSname(String sname) { this.sname = sname; } public Address getAddress() { return address; } public void setAddress(Address address) { this.address = address; } } |
Test.java
package com.java4coding;
import java.util.List;
import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; import javax.persistence.Query;
public class Test { public static void main(String[] args) { EntityManagerFactory emf = Persistence.createEntityManagerFactory("StudentPU"); EntityManager em = emf.createEntityManager(); em.getTransaction().begin(); Query query = em.createNativeQuery("SELECT * FROM STUDENT", Student.class);
List<Student> results = (List<Student>)query.getResultList();
for(Student s: results) { System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~" ); if (s.getSname() != null) { System.out.println("Student name: " + s.getSname()); } if (s.getSid() != 0) { System.out.println("Student ID: " + s.getSid()); } if (s.getAddress().getCity() != null) { System.out.println("Student City: " + s.getAddress().getCity()); } if (s.getAddress().getCity() != null) { System.out.println("Student City: " + s.getAddress().getCity()); } if (s.getAddress().getZipcode() != null) { System.out.println("Student Zipcode: " + s.getAddress().getZipcode()); } System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~" ); }
em.getTransaction().commit(); } } |
Project directory structure
Output:
Hibernate: SELECT * FROM STUDENT Hibernate: select address0_.aid as aid1_0_0_, address0_.city as city2_0_0_, address0_.zipcode as zipcode3_0_0_ from ADDRESS address0_ where address0_.aid=? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Student name: Manu Manjunatha Student ID: 1 Student City: Bangalore Student City: Bangalore Student Zipcode: 560010 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Student name: Advith Tyagraj Student ID: 2 Student City: Bangalore Student City: Bangalore Student Zipcode: 560010 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Student name: Likitha Student ID: 3 Student City: Bangalore Student City: Bangalore Student Zipcode: 560010 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Student name: Tyagraj Student ID: 4 Student City: Bangalore Student City: Bangalore Student Zipcode: 560010 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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