JSF interaction with database
Following bean's database related code is working in simple Java application but when i use it within JSF page it is giving Java null pointer exception error. Thanks in advance.
Bean class:-
import java.io.Serializable;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
@ManagedBean
@SessionScoped
public class Db implements Serializable{
int eId;
public int geteId() {
return eId;
}
public void seteId(int eId) {
this.eId = eId;
}
public static Connection getConnection() throws Exception {
String driver = "oracle.jdbc.driver.OracleDriver";
String url = "jdbc:oracle:thin:@localhost:1521:globldb3";
String username = "scott";
String password = "tiger";
Class.forName(driver);
Connection conn = DriverManager.getConnection(url, username, password);
return conn;
}
public String addEmployee() throws Exception{
Connection conn = null;
PreparedStatement pstmt = null;
try {
int a = this.eId;
conn = getConnection();
String query = "INSERT INTO c(n) VALUES(?)";
pstmt = conn.prepareStatement(query);
pstmt.setInt(1,a);
pstmt.executeUpdate(); // execute insert statement
return "success";
} catch (Exception e) {
e.printStackTrace();
return "failure";
} finally {
pstmt.close();
conn.close();
}
}
}
Following is my JSF page
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core">
<body>
<h:form>
<p>Enter value <h:inputText value="#{db.eId}"/> </p>
<p> <h:commandButton value="Add record" action="#{db.addEmployee}"/> </p>
</h:form>
</body>
</html>
Following is stack trace
javax.faces.el.EvaluationException: java.lang.NullPointerException
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:787)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1252)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:312)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:306)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:108)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:558)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:379)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:259)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:281)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
at erpJavaFiles.Employee.addEmployee(Employee.java:118)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java开发者_开发知识库:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.el.parser.AstValue.invoke(AstValue.java:262)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
... 23 more
Here,
} finally {
pstmt.close();
conn.close();
}
you aren't checking if they are null before you close them. If an exception is been thrown upon connecting, they will stay null. Fix it as follows:
} finally {
if (pstmt != null) pstmt.close();
if (conn != null) conn.close();
}
There are no other potential causes for a NPE in the addEmployee() method. I see that you've an e.printStackTrace() call in the catch block. Read this one for the real cause of the problem. I guess that it's a ClassNotFoundException on the JDBC driver class, because you forgot to put the JDBC driver in /WEB-INF/lib folder of the webapp.
加载中,请稍侯......
精彩评论