Making a program that saves users a database I get the following error. The program begins with a index.html, wherein there is a button qual to which tightens it goes to addUser servlet that executes the method.
Error:
SEVERE: Servlet.service() for servlet [servlet.TestEJB] in context with path [/activitat] threw exception
java.lang.NullPointerException
at servlet.TestEJB.doPost(TestEJB.java:40)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1517)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1474)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
Servlet:
@WebServlet("/TestEJB")
public class TestEJB extends HttpServlet{
private static final long serialVersionUID = 1L;
MissatgesEJB meuEJB;
/* (non-Javadoc)
* @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
*/
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = resp.getWriter()) {
out.println("<!DOCTYPE html>");
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet TestEJB</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Proves Whatsapp</h1>");
Usuaris usuari = new Usuaris("robert_1994", "Paucasals33", "Bruch");
out.println("Insertant Usuari... " + meuEJB.insertarUsuari(usuari) + "<br/>");
out.println("</body>");
out.println("</html>");
}
}
}
Method:
public class MissatgesEJB {
@PersistenceUnit
EntityManagerFactory emf;
public String insertarUsuari(Usuaris u) {
EntityManager em = emf.createEntityManager();
try {
// Excriu a la BD.
em.persist(u);
// Forçem a que escrigui ara ala BD.
em.flush();
return "ok";
} catch (Exception ex) {
return ex.getMessage();
} finally {
em.close();
}
}
}
Persistence.xml:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="JPA-1" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>beans.Historial</class>
<class>beans.Missatges</class>
<class>beans.Usuaris</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost/bdwhatsapp" />
<property name="javax.persistence.jdbc.user" value="marti" />
<property name="javax.persistence.jdbc.password" value="Paucasals33" />
<property name="javax.persistence.schema-generation.database.action"
value="none" />
</properties>
</persistence-unit>
</persistence>
