java.lang.Nullpointerexception Error in JDBC Connection with WS + Postgres

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I am creating a WS that connects to a DB Postgresql and performs a query in a single table.

I try to run it locally, but the problem is when running the application gives the following error:

HTTP 500 status - Internal Server Error

type: Exception report

message: Internal Server Error

description: The server encountered an internal error ({0}) that prevented it from meet this request.

exception

javax.servlet.ServletException: java.lang.NullPointerException causa-raiz

java.lang.NullPointerException

Note: Full exception stack crawls and their root causes are available in Glassfish Server Open Source Edition 4.0 logs .

I believe it is not so complex, but as I have no experience with language, I am having difficulties.

My codes are:

Dbconnection.java

package br.com.dbconnection;

import br.com.findfriends.entidade.Friend;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class DBConnection {  

    private String databaseURL = "jdbc:postgresql://localhost:8080/wsfindfriends";  
    private String usuario = "postgres";  
    private String senha = "senhaPostgres";  
    private String driverName = "org.postgresql.Driver";  
    private PreparedStatement stmt = null;  
    private ResultSet rs = null;  
    public Connection conn = null;  

    public void DBConnection() {          
        try {  
            Class.forName(driverName).newInstance();  
            this.conn = DriverManager.getConnection(databaseURL, usuario, senha);  
            System.out.println("Conexão obtida com sucesso.");  
        }  
        catch (SQLException ex) {  
            System.out.println("SQLException: " + ex.getMessage());  
            System.out.println("SQLState: " + ex.getSQLState());  
            System.out.println("VendorError: " + ex.getErrorCode());  
        }  
        catch (Exception e) {  
            System.out.println("Problemas ao tentar conectar com o banco de dados: " + e);  
        }        
    }  

    public List<Friend> executeQuery(String query) {  
        try {  
            List<Friend> list = new ArrayList<Friend>();  
            this.stmt = this.conn.prepareStatement(query);  
            this.rs = this.stmt.executeQuery();              

            while (rs.next()) {  
                // criando o objeto Friend  
                Friend friend = new Friend();  
                friend.setId(rs.getInt("id"));  
                friend.setNome(rs.getString("nome"));  
                friend.setNome(rs.getString("fone"));  

                // adicionando o objeto à lista  
                list.add(friend);  
            }  
            this.close();  
            return list;  
        }  
        catch (SQLException e) {  
            throw new RuntimeException(e);  
        }  
    }  

    public void close(){  
        try {  
            this.stmt.close();  
            this.rs.close();  
            this.conn.close();  
        }  
        catch (SQLException e) {  
            throw new RuntimeException(e);  
        }  
    }      
}

Findfriendsservice.java

package br.com.findfriends;

import br.com.dbconnection.DBConnection;
import br.com.findfriends.entidade.Friend;
import com.google.gson.Gson;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.UriInfo;
import javax.ws.rs.PathParam;
import javax.ws.rs.Consumes;
import javax.ws.rs.Produces;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PUT;
import javax.ws.rs.core.MediaType;

@Path("findfriends")  
public class FindFriendsService {  

    @Context  
    private UriInfo context;  

    /** 
     * Creates a new instance of FindFriendsService 
     */  
    public FindFriendsService() {  
    }  

    /** 
     * Retrieves representation of an instance of br.com.findfriends.FindFriendsService 
     * @return an instance of java.lang.String 
     */  
    @GET  
    @Produces(MediaType.APPLICATION_JSON)  
    public String getJson() {  
        //TODO return proper representation object          
        DBConnection dbc = new DBConnection();  
        List<Friend> list = new ArrayList<Friend>();  
        list = dbc.executeQuery("SELECT * FROM locationfriends");  

        Gson gson = new Gson();  
        return gson.toJson(list);          
    }  

    /** 
     * PUT method for updating or creating an instance of FindFriendsService 
     * @param content representation for the resource 
     * @return an HTTP response with content of the updated or created resource. 
     */  
    @PUT  
    @Consumes(MediaType.APPLICATION_JSON)  
    public void putJson(String content) {  
    }  
}

Friend.java

package br.com.findfriends.entidade;

public class Friend {  

    private int id;  
    private String nome, fone;  

    public int getId() {  
        return id;  
    }  

    public void setId(int id) {  
        this.id = id;  
    }  

    public String getNome() {  
        return nome;  
    }  

    public void setNome(String nome) {  
        this.nome = nome;  
    }  

    public String getFone() {  
        return fone;  
    }  

    public void setFone(String fone) {  
        this.fone = fone;  
    }  
}

=====================================

Edit: Stacktrace:

java.lang.NullPointerException
    at br.com.dbconnection.DBConnection.executeQuery(DBConnection.java:51)
    at br.com.findfriends.FindFriendsService.getJson(FindFriendsService.java:52)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:125)
    at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$TypeOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:195)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:91)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:346)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:341)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:101)
    at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:224)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:198)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:946)
    at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:323)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:372)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:335)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:218)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
    at java.lang.Thread.run(Thread.java:745)
java web-service postgresql connection jdbc

  • Please paste the stack-trace into a Pastebin for us, without it you won’t know the problem.

  • Where you are hosting your webservice?

  • +Edgar Muniz Berlinck, I didn’t know what stacktrace was, but I did a quick search and I think I figured it out. Post updated. +Math, I’m testing locally only.

  • What is line 51 on your DBConnection.java?

  • line 51: this.stmt = this.conn.prepareStatement(query);

  • No further exceptions were made? Because the error is indicating that the variable conn is not referencing an object, however it should have been initialized in the constructor, but it is possible that the constructor has not run entirely if there has been a problem in it.

  • No. When I run the application gives the bug right away without launching exception.

  • 1

    Is your Postgresql actually running on port 8080? By default this is the Glassfish port. In the connection URL it is not necessary to put the port, unless Postgresql is running on another port that is not the default.

  • when running the application, access the webservice by the url: http://localhost:8080/wsfindfriends/webresources/findfriends. In case I try to access http://localhost/wsfindfriends/webresources/findfriends, removing the door 8080, gives Notfound. Has any relationship?

  • 1

    Yes, for you to access the application you really must access localhost:8080/Your application, but the URL of the connection to the database is different, it is not the same that is used to access the application.

  • how can I find out if this URL is correct? And if not, how to know the correct url to use?

Show 6 more comments

1 answer

2


What’s going on is this:

databaseURL, is pointing to the application server port and not the database server;

So, databaseURL it must be like this:

jdbc:postgresql://localhost/nomeDoSeuBancoDeDados

Because it is not necessary to put the port in the connection URL with the bank, because when not placed the default port is used. It is only necessary when the door is changed and I believe that is not your case.

To access your application continue using:

localhost:8080/wsfindfriends/webresources/findfriends

  • Dude, that’s right. I had copied the third party script that was setting that door, in the end it was just removing it. Thank you! What a primary error huh. T_T

  • Rsrsr. Nice to have helped.

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