Null Pointer Exception in POST method in jersey - nullpointerexception

Question

I am building a web project using jersey and hibernate. I am testing crud operations in postman. For POST method i get a null pointer exception and I don't know how to solve. Please help me. I am new in jersey.
Below is my code and my full stack trace.
BookRepository.com
package com.bookstrore.repository;
import java.util.ArrayList;
import java.util.List;
import org.hibernate.Transaction;
import org.hibernate.Session;
import org.hibernate.Query;
import com.bookstrore.model.Book;
import com.bookstrore.model.SessionUtil;
//import com.pluralsight.model.User;
public class BookRepositoryStub {
public void createBook(Book book) {
Session session = SessionUtil.getSession();
Transaction tx = session.beginTransaction();
createBook(session,book);
tx.commit();
session.close();
}
private void createBook(Session session, Book bo){
Book book=new Book();
book.setBook_id(bo.getBook_id());
book.setBook_title(bo.getBook_title());
book.setBook_author(bo.getBook_author());
book.setBook_description(bo.getBook_description());
book.setBook_price(bo.getBook_price());
session.save(book);
}
public List<Book> getBooks(){
Session session = SessionUtil.getSession();
Query query = session.createQuery("from Book");
List<Book> books = query.list();
session.close();
return books;
}
public int delete(int book_id){
Session session = SessionUtil.getSession();
Transaction tx = session.beginTransaction();
String hql = "delete from Book where book_id = :book_id";
Query query = session.createQuery(hql);
query.setInteger("book_id",book_id);
int rowCount = query.executeUpdate();
System.out.println("Rows affected: " + rowCount);
tx.commit();
session.close();
return rowCount;
}
public int update(int book_id, Book bo){
if(book_id <=0)
return 0;
Session session = SessionUtil.getSession();
Transaction tx = session.beginTransaction();
String hql = "update Book set book_title = :book_title, book_author = :book_author, book_description = :book_description, book_price = :book_price, where book_id = :book_id";
Query query = session.createQuery(hql);
query.setInteger("book_id", book_id);
query.setString("book_title",bo.getBook_title());
query.setString("book_author",bo.getBook_author());
query.setString("book_description",bo.getBook_description());
query.setInteger("book_price",bo.getBook_price());
int rowCount = query.executeUpdate();
System.out.println("Rows affected: " + rowCount);
tx.commit();
session.close();
return rowCount;
}
}
BookResource.java
package com.bookstrore;
import java.util.List;
import javax.ws.rs.Consumes;
import javax.ws.rs.DELETE;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.Status;
import com.bookstrore.model.Book;
//import com.ebook.model.User;
//import com.ebook.repository.BookRepository;
import com.bookstrore.repository.BookRepositoryStub;
#Path("books")
public class BookResource {
//private BookRepository bookRepository=new BookRepositoryStub();
#GET
#Produces("application/json")
public List<Book> getBook() {
BookRepositoryStub book = new BookRepositoryStub();
List books = book.getBooks();
return books;
}
#DELETE
#Path("{bookId}")
#Consumes("application/json")
public Response delete(#PathParam("bookId") int book_id){
BookRepositoryStub book = new BookRepositoryStub();
int count = book.delete(book_id);
if(count==0){
return Response.status(Response.Status.BAD_REQUEST).build();
}
return Response.ok().build();
}
#PUT
#Path("{bookId}")
//#Consumes(MediaType.APPLICATION_JSON)
#Consumes("application/json")
public Response update(#PathParam("bookId") int book_id, Book bo){
BookRepositoryStub book = new BookRepositoryStub();
int count = book.update(book_id, bo);
if(count==0){
return Response.status(Response.Status.BAD_REQUEST).build();
}
return Response.ok().build();
}
#POST
#Path("book")
#Consumes("application/json")
//#Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
public Response createBook(Book bo){
bo.setBook_title(bo.getBook_title());
bo.setBook_author(bo.getBook_author());
bo.setBook_description(bo.getBook_description());
bo.setBook_price(bo.getBook_price());
BookRepositoryStub book = new BookRepositoryStub();
book.createBook(bo);
return Response.ok().build();
}
}
Book.java
package com.bookstrore.model;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
#Entity
#Table(name="book")
public class Book {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private int book_id;
#Column
private String book_title;
#Column
private String book_author;
#Column
private String book_description;
#Column
private int book_price;
public int getBook_id() {
return book_id;
}
public void setBook_id(int book_id) {
this.book_id = book_id;
}
public String getBook_title() {
return book_title;
}
public void setBook_title(String book_title) {
this.book_title = book_title;
}
public String getBook_author() {
return book_author;
}
public void setBook_author(String book_author) {
this.book_author = book_author;
}
public String getBook_description() {
return book_description;
}
public void setBook_description(String book_description) {
this.book_description = book_description;
}
public int getBook_price() {
return book_price;
}
public void setBook_price(int book_price) {
this.book_price = book_price;
}
}
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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.bookstore</groupId>
<artifactId>BookStore</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>BookStore</name>
<build>
<finalName>BookStore</finalName>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.5.1</version>
<inherited>true</inherited>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.2.3</version>
</dependency>
<dependency>
<groupId>org.glassfish.jersey</groupId>
<artifactId>jersey-bom</artifactId>
<version>${jersey.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.glassfish.jersey.containers</groupId>
<artifactId>jersey-container-servlet-core</artifactId>
<!-- use the following artifactId if you don't need servlet 2.x compatibility -->
<!-- artifactId>jersey-container-servlet</artifactId -->
<version>2.22.1</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.3.10.Final</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.34</version>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.media</groupId>
<artifactId>jersey-media-moxy</artifactId>
</dependency>
</dependencies>
<properties>
<jersey.version>2.22.1</jersey.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<!-- This web.xml file is not required when using Servlet 3.0 container,
see implementation details http://jersey.java.net/nonav/documentation/latest/jax-rs.html -->
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
<servlet-name>Jersey Web Application</servlet-name>
<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>com.bookstrore</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Jersey Web Application</servlet-name>
<url-pattern>/webapi/*</url-pattern>
</servlet-mapping>
</web-app>
Stack Trace:
<pre>java.lang.NullPointerException
com.bookstrore.BookResource.createBook(BookResource.java:72)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:144)
org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:161)
org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$ResponseOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:160)
org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:99)
org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:389)
org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:347)
org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:102)
org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:326)
org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
org.glassfish.jersey.internal.Errors.process(Errors.java:315)
org.glassfish.jersey.internal.Errors.process(Errors.java:297)
org.glassfish.jersey.internal.Errors.process(Errors.java:267)
org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:305)
org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1154)
org.glassfish.jersey.servlet.WebComponent.serviceImpl(WebComponent.java:471)
org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:425)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:383)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:336)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:223)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
</pre>
I am looking forward for your help! Please! Thank you!

Answer 1

I believe that there are two problems in your code that by changing them, your problem will be solved.
First of all, in your class "Book" you need to write the constructor with all the parameters, besides the id (that is auto-generated by hibernate), and also have a no-argument constructor. So add this:
And on the other hand, you have to declare your class "Book" as #XmlRootElement as you did with #Entity and #Table.
This video explains the why of all of this and it is also a great tutorial for beginners with web services and jersey:
https://www.youtube.com/watch?v=BaZdlJSts5A&list=PLqq-6Pq4lTTZh5U8RbdXq0WaYvZBz2rbn&index=14
Hope this helps! Your Book class should look like this:
#Entity
#Table(name="book")
#XmlRootElement
public class Book {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private int book_id;
#Column
private String book_title;
#Column
private String book_author;
#Column
private String book_description;
#Column
private int book_price;
public Book(){ }
public Book(String title, String author, String description, int price){
book_title = title;
book_author = author;
book_description = description;
book_price = price;
}
public int getBook_id() {
return book_id;
}
public void setBook_id(int book_id) {
this.book_id = book_id;
}
public String getBook_title() {
return book_title;
}
public void setBook_title(String book_title) {
this.book_title = book_title;
}
public String getBook_author() {
return book_author;
}
public void setBook_author(String book_author) {
this.book_author = book_author;
}
public String getBook_description() {
return book_description;
}
public void setBook_description(String book_description) {
this.book_description = book_description;
}
public int getBook_price() {
return book_price;
}
public void setBook_price(int book_price) {
this.book_price = book_price;
}
}