In this post, we will see JPA EntityManager remove() example using Spring Boot and Oracle.
The remove() method used to remove an entity and defined in the EntityManager interface as below.
public void remove(Object entity); – Used to remove an entity.
Note – The EntityManger interface is available in javax.persistence package. The remove() method throws IllegalArgumentException if the instance is not an entity or is a detached entity. In Spring Data JPA CrudRepository delete() method internally uses EntityManager remove() method. See an example here.
Let’s see how to use EntityManager remove() method.
First, we need to create an EntityManger reference.
@PersistenceContext
private EntityManager entityManger;
Using this we can call persist() method.
package com.javatute.impl;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.javatute.entity.Student;
import com.javatute.service.StudentService;
@Service("studentServiceImpl")
public class StudentServiceImpl implements StudentService {
@PersistenceContext
private EntityManager entityManger;
@Transactional
public Student deleteStudent(Student student) {
if (entityManger.contains(student)) {
entityManger.remove(student);
} else {
entityManger.remove(entityManger.merge(student));
}
return student;
}
}
Did you notice in above code snippet we are checking entityManger.contains(student)? If the entityManger doesn’t contain the entity we want to delete then first we need to call merge() method then only we should call remove() method otherwise we will get java.lang.IllegalArgumentException: Removing a detached instance.
Note – Implementation of EntityManger remove() method has been given in Hibernate’s SessionImpl.java as below.
public void remove(Object entity) {
delete( entity );
}
Let’s see JPA EntityManager remove() example using Spring Boot and Oracle.
Open eclipse and create maven project, Don’t forget to check ‘Create a simple project (skip)’ click on next. Fill all details(GroupId – entitymanager, ArtifactId – entitymanager and name – entitymanager) and click on finish. Keep packaging as the jar.
Modify pom.xml
<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>entitymanager</groupId>
<artifactId>entitymanager</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>entitymanager</name>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.2.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>com.oracle</groupId>
<artifactId>ojdbc6</artifactId>
<version>11.2.0.3</version>
</dependency>
</dependencies>
<build>
<finalName>${project.artifactId}</finalName>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<fork>true</fork>
<executable>C:\Program Files\Java\jdk1.8.0_131\bin\javac.exe</executable>
</configuration>
</plugin>
</plugins>
</build>
</project>
Note – In pom.xml we have defined javac.exe path in configuration tag. You need to change accordingly i.e where you have installed JDK.
If you see any error for oracle dependency then follow these steps.
Let’s see the directory structure of JPA EntityManager remove() example as below.
Directory structure –
Let’s see about JPA EntityManager find() method.
Student.java
package com.javatute.entity;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class Student {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;
@Column(name = "name")
private String name;
@Column(name = "roll_number")
private String rollNumber;
@Column(name = "university")
String university;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getRollNumber() {
return rollNumber;
}
public void setRollNumber(String rollNumber) {
this.rollNumber = rollNumber;
}
public String getUniversity() {
return university;
}
public void setUniversity(String university) {
this.university = university;
}
}
StudentController.java
package com.javatute.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import com.javatute.entity.Student;
import com.javatute.service.StudentService;
@RestController
@RequestMapping(value = "/student")
public class StudentController {
@Autowired
private StudentService studentService;
@RequestMapping(value = "/save", method = RequestMethod.POST)
@ResponseBody
public Student saveStudent(@RequestBody Student student) {
Student studentResponse = (Student) studentService.saveStudent(student);
return studentResponse;
}
@RequestMapping(value = "/delete", method = RequestMethod.POST)
@ResponseBody
public Student deleteStudent(@RequestBody Student student) {
Student studentResponse = (Student) studentService.deleteStudent(student);
return studentResponse;
}
@RequestMapping(value = "/find/{id}", method = RequestMethod.GET)
@ResponseBody
public Student getStudent(@PathVariable int id) {
Student studentResponse = (Student) studentService.getStudent(id);
return studentResponse;
}
}
We have seen controller and serviceimpl, interface for JPA EntityManager remove() example.
Note – See more details about @Controller and RestController here.
StudentService.java – interface
package com.javatute.service;
import org.springframework.stereotype.Component;
import com.javatute.entity.Student;
@Component
public interface StudentService {
public Student saveStudent(Student student);
public Student deleteStudent(Student student);
public Student getStudent(int id);
}
Note – See here more about @Component, @Controller, @Service and @Repository annotations here.
StudentServiceImpl.java
package com.javatute.impl;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.javatute.entity.Student;
import com.javatute.service.StudentService;
@Service("studentServiceImpl")
public class StudentServiceImpl implements StudentService {
@PersistenceContext
private EntityManager entityManger;
@Transactional
public Student saveStudent(Student student) {
entityManger.persist(student);
return student;
}
@Transactional
public Student deleteStudent(Student student) {
entityManger.detach(student);
return student;
}
@Transactional
public Student getStudent(int id) {
Student response = (Student) entityManger.find(Student.class, id);
return response;
}
}
SpringMain.java
package com.javatute.main;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.ComponentScan;
@SpringBootApplication
@ComponentScan(basePackages = "com.*")
@EntityScan("com.javatute.entity")
public class SpringMain {
public static void main(String[] args) {
SpringApplication.run(SpringMain.class, args);
}
}
Note – See more details about @ComponentScan here.
Configuration file for JPA EntityManager remove() example.
JpaConfig.java
package com.javatute.config;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
@Configuration
@EnableJpaRepositories(basePackages = "com.javatute.repository")
public class JpaConfig {
}
Note – See more details about @Configuration annotations here.
application.properties
# Connection url for the database spring.datasource.url=jdbc:oracle:thin:@localhost:1521:XE spring.datasource.username=SYSTEM spring.datasource.password=oracle2 spring.datasource.driver-class-name=oracle.jdbc.driver.OracleDriver # Show or not log for each sql query spring.jpa.show-sql = true spring.jpa.properties.hibernate.format_sql=true spring.jpa.hibernate.ddl-auto =create spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.Oracle10gDialect server.port = 9091 #show sql values logging.level.org.hibernate.type.descriptor.sql=trace #hibernate.show_sql = true #spring.jpa.hibernate.logging.level.sql =FINE #show sql statement #logging.level.org.hibernate.SQL=debug
Let’s run the SpringMain class(run as java application).
Perform save operation first using below REST API.
http://localhost:9091/student/save
{
"name": "john",
"rollNumber": "120",
"university":"rgtu"
}
Response Data.
{
"id": 1,
"name": "john",
"rollNumber": "120",
"university": "rgtu"
}
Below query get generated while saving student entity using persist() method.
Hibernate:
select
hibernate_sequence.nextval
from
dual
Hibernate:
insert
into
student
(name, roll_number, university, id)
values
(?, ?, ?, ?)
DELETE – http://localhost:9091/student/delete
delete
from
student
where
id=?
http://localhost:9091/student/find/1
If you try to fetch student using id 1, will not get any record.
That’s all about JPA EntityManager remove() example using Spring Boot and Oracle.
Spring Data JPA examples.
- Spring Data JPA greater than Example
- Spring Data JPA less than Example
- Spring Data JPA IsNull Example Using Spring Boot
- Spring Data findById() Vs getOne()
- Spring Data JPA CrudRepository findById()
- Spring Data JPA JpaRepository getOne()
- Spring Data CrudRepository saveAll() and findAll().
- Spring Data CrudRepository existsById()
- Spring Data JPA delete() vs deleteInBatch()
- Spring Data JPA deleteAll() Vs deleteAllInBatch()
- Spring Data JPA JpaRepository deleteAllInBatch()
- Spring Data JPA deleteInBatch() Example
- Spring Data JPA JpaRepository saveAndFlush() Example
- Spring Data JPA CrudRepository count() Example
- Spring Data JPA CrudRepository delete() and deleteAll()
- Spring Data JPA CrudRepository deleteById() Example
- CrudRepository findAllById() Example Using Spring Boot
- Spring Data CrudRepository save() Method.
- Sorting in Spring Data JPA using Spring Boot.
- Spring Data JPA example using spring boot.
- Spring Data JPA and its benefit.
Other Spring Data JPA and Hibernate tutorials.
- @Version Annotation Example In Hibernate.
- Hibernate Validator Constraints Example Using Spring Boot.
- @Temporal Annotation Example In Hibernate/Jpa Using Spring Boot.
- Hibernate Table Per Concrete Class Spring Boot.
- Hibernate Table Per Subclass Inheritance Spring Boot.
- Hibernate Single Table Inheritance using Spring Boot.
- One To One Mapping Annotation Example in Hibernate/JPA using Spring Boot and Oracle.
- One To One Bidirectional Mapping Example In Hibernate/JPA Using Spring Boot and Oracle.
- One To Many Mapping Annotation Example In Hibernate/JPA Using Spring Boot And Oracle.
- Many To One Unidirectional Mapping In Hibernate/JPA Annotation Example Using Spring Boot and Oracle.
- One To Many Bidirectional Mapping In Hibernate/JPA Annotation Example Using Spring Boot and Oracle.
- Many To Many Mapping Annotation Example In Hibernate/JPA Using Spring Boot And
EntityManger docs.
Summary – We have seen about JPA EntityManager remove() example.
