java.lang.IllegalStateException: Failed to execute - CommandLineRunner NullPointer Excaption - spring-boot

Question

Repository
package com.example.demo.jpa;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.transaction.Transactional;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
import com.example.demo.entity.Person;
#Repository
#Transactional
public class RepositoryJpa {
#PersistenceContext
EntityManager entityManager;
//#Autowired
Person person = new Person();
public Person findById(int id) {
System.out.println("value of parameter id is "+id);
return entityManager.find(Person.class,id);
}
public Person update(Person person) {
return entityManager.merge(person);
}
}
Entity table:
package com.example.demo.entity;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
#Entity
//#Table(name="person")
public class Person {
#Id
private int id;
private String name;
private String location;
private String birth_date;
// public Person(int i, String string, String string2, String string3) {}
public Person(int id, String name, String location, String birth_date) {
// super();
this.id = id;
this.name = name;
this.location = location;
this.birth_date = birth_date;
}
public Person(String name, String location, String birth_date) {
// super();
this.name = name;
this.location = location;
this.birth_date = birth_date;
}
public Person() {
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
System.out.println("i called setID=" + this.id);
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
System.out.println("i called setName=" + this.name);
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
System.out.println("i called setLocation=" + this.location);
}
public String getBirth_date() {
return birth_date;
}
public void setBirth_date(String birth_date) {
this.birth_date = birth_date;
// System.out.println("i called setBirth_ID="+this.birth_date);
}
/*
* #Override public String toString() { return "Person [id=" + id + ", name=" +
* name + ", location=" + location + ", birth_date=" + birth_date + ", getId()="
* + getId() + ", getName()=" + getName() + ", getLocation()=" + getLocation() +
* ", getBirth_date()=" + getBirth_date() + "]"; }
*/
}
SpringBootApplication
package com.example.demo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.context.annotation.Bean;
import com.example.demo.entity.Person;
import com.example.demo.jpa.RepositoryJpa;
#SpringBootApplication
public class JpaDemoApplication implements CommandLineRunner {
private Logger logger=LoggerFactory.getLogger(this.getClass());
//#Autowired
Person person = new Person();
RepositoryJpa repo = new RepositoryJpa();
public static void main(String[] args) {
// TODO Auto-generated method stub
SpringApplication.run(JpaDemoApplication.class, args);
}
#Override
public void run(String... args) throws Exception {
// TODO Auto-generated method stub
System.out.println("hello all");
logger.info("find by id -> {}", repo.findById(2));
logger.info("insert user-> {}",repo.update(new Person(5,"gaurav","chicago","05/06/82")));
}
}
Application Properties
spring.h2.console.enabled=true
#spring.datasource.url=jdbc:h2:mem:testdb
#spring.batch.job.enabled=false
spring.jpa.show-sql=true
##EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
spring.jpa.defer-datasource-initialization=true
I'm a beginner to SpringBoot and I don't know what wrong I'm doing related to entity manager method it giving the error of and also #Autowired not working, I'm manually creating the object!
Help me please!!!
Console error screenshot also shared below please check:
Failed to execute CommandLineRunner
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:780) ~[spring-boot-2.6.4.jar:2.6.4]
at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:761) ~[spring-boot-2.6.4.jar:2.6.4]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:310) ~[spring-boot-2.6.4.jar:2.6.4]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1312) ~[spring-boot-2.6.4.jar:2.6.4]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301) ~[spring-boot-2.6.4.jar:2.6.4]
at com.example.demo.JpaDemoApplication.main(JpaDemoApplication.java:31) ~[classes/:na]
Caused by: java.lang.NullPointerException: null
at com.example.demo.jpa.RepositoryJpa.update(RepositoryJpa.java:31) ~[classes/:na]
at com.example.demo.JpaDemoApplication.run(JpaDemoApplication.java:46) ~[classes/:na]
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:777) ~[spring-boot-2.6.4.jar:2.6.4]
... 5 common frames omitted
console

Answer 1

You should Autowire the repository bean in JpaDemoApplication class, you should never create an object for spring component using new keyword
#SpringBootApplication
public class JpaDemoApplication implements CommandLineRunner {
private Logger logger=LoggerFactory.getLogger(this.getClass());
#Autowired
RepositoryJpa repositoryJpa;
public static void main(String[] args) {
// TODO Auto-generated method stub
SpringApplication.run(JpaDemoApplication.class, args);
}
#Override
public void run(String... args) throws Exception {
// TODO Auto-generated method stub
System.out.println("hello all");
logger.info("find by id -> {}", repo.findById(2));
logger.info("insert user-> {}",repo.update(new Person(5,"gaurav","chicago","05/06/82")));
}
}