MyEclipseのストラットを使用してDerbyデータベースに接続できません

Question

私はstrutsとMyEclipse IDEを初めて使用しています。
私はユーザ名とパスワードを取り、MyEclipseのデフォルトのデータベースすなわちダービーに保管しようとするとログインアプリケーションを開発しました。
しかし、Derby DBとの接続に失敗し、ログインの詳細を保存できません。
私のプロジェクトのlibフォルダにderby jarファイルを置き、DerbyデータベースのAPPフォルダテーブルの下に「ログイン」テーブルを作成しました

私を助けてください。

LoginFormBean.java

package info.strutspkg; 

import javelin.servlet.http.HttpServletRequest; 

import org.apache.struts.action.ActionErrors; 
import org.apache.struts.action.ActionForm; 
import org.apache.struts.action.ActionMapping; 
import org.apache.struts.action.ActionMessage; 

public class LoginFormBean extends ActionForm { 

private String username = null; 
private String password = null; 

public ActionErrors validate(ActionMapping mapping, 
     HttpServletRequest request) { 

    ActionErrors actionErrors = new ActionErrors(); 

    if(username == null || username.length() < 1) { 
     actionErrors.add("userName", new ActionMessage("error.username")); 
    } 
    try { 
    if(password == null || password.length()<1) { 
     actionErrors.add("password", new ActionMessage("error.password")); 
    } 
    }catch(Exception e) { 
     e.printStackTrace(); 
    } 
    return actionErrors ; 
} 

public void setUsername(String username) 
{ 
    this.username = username; 
} 
public String getUsername() 
{ 
    return username; 
} 
public void setPassword(String password) 
{ 
    this.password = password; 
} 
public String getPassword() 
{ 
    return password; 
} 
} 

LoginActionClass.java

package info.strutspkg; 


import java.sql.Connection; 

import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 

import login.logindao.Logindao; 

import org.apache.struts.action.*; 

public class LoginActionClass extends Action{ 

    public ActionForward execute(ActionMapping mapping,ActionForm form,HttpServletRequest request,HttpServletResponse response)throws Exception 
    { 
     Connection con=null; 
      String key=null; 
    try{ 

     LoginFormBean lf = (LoginFormBean)form; 
     String uname = lf.getUsername(); 
     String pwd = lf.getPassword(); 


     Logindao dao=new Logindao(); 

     int i=dao.insert(uname,pwd); 

     if(i>0){ 
     key="success"; 
     } 
     else 
     { 
     key="failure"; 
     } 
     } 
     catch(Exception e){ 
     e.printStackTrace(); 

     } 
    return mapping.findForward(key); 
    } 
    } 

Logindao.java

package login.logindao; 

import java.sql.Connection; 
import java.sql.PreparedStatement; 
import java.sql.SQLException; 

import db.dbconnection.DBConnect; 

public class Logindao { 

    public int insert(String uname,String pwd){ 
      int r=0; 
      PreparedStatement ps = null; 
      //get connection object from DBConnection class 
      Connection conn = DBConnect.createConnection(); 
      System.out.println("Connection"+conn); 

      try{ 
      //use PreparedStatement to insert the values of username and password 
      ps=conn.prepareStatement("insert into login(username,password) values(?,?)"); 
      ps.setString(1, uname); 
      ps.setString(2, pwd); 
      r = ps.executeUpdate(); 
      } 
      catch(SQLException ex) { 
      try { 
      ps.close(); 
      conn.close(); 
      } catch (SQLException e) { 
      e.printStackTrace(); 
      } 
      System.err.println("SQLException: " + ex.getMessage()); 
      } 
      return r; 

     } 

} 

DBConnect.java

package db.dbconnection; 

import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.Statement; 

public class DBConnect { 

     public static Connection createConnection(){ 

    Connection conn = null; 
    String url = "jdbc:derby://localhost:1527/myeclipse/derby;create=true"; 
    String userName="lalitha"; 
    String password="lalitha"; 
    String tableName = "login"; 


     try 
      { 
       Class.forName("org.apache.derby.jdbc.ClientDriver").newInstance(); 
       //Get a connection 
       conn = DriverManager.getConnection(url,userName,password); 
      } 
      catch (Exception except) 
      { 
       except.printStackTrace(); 
      } 
      return conn; 
     } 
     } 

のStackTrace：

**Connectionorg.apache.derby.client.net.NetConnection40@161401f 
java.lang.NullPointerException 
    at login.logindao.Logindao.insert(Logindao.java:27) 
    at info.strutspkg.LoginActionClass.execute(LoginActionClass.java:28) 
    at org.apache.struts.chain.commands.servlet.ExecuteAction.execute(ExecuteAction.java:58) 
    at org.apache.struts.chain.commands.AbstractExecuteAction.execute(AbstractExecuteAction.java:67) 
    at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51) 
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190) 
    at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:304) 
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190) 
    at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283) 
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913) 
    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:810) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) 
    at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:81) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178) 
    at org.jboss.web.tomcat.security.CustomPrincipalValve.invoke(CustomPrincipalValve.java:39) 
    at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:153) 
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:59) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148) 
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856) 
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:744) 
    at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527) 
    at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112) 
    at java.lang.Thread.run(Thread.java:662) 
WARN [ActionMapping] Unable to find 'null' forward. 

Answer 1

それは、データベースの作成が例外をキャッチしたときに機能createConnection()はNULLを返しますので、あなたは、NullPointerExceptionが取得：

Connection conn = null; 
    try 
     { 
      ... 
     } 
     catch (Exception except) 
     { 
      except.printStackTrace(); 
     } 
     //conn is null 
     return conn; 

except.printStackTrace();の出力はhあなたはその特定のエラーを見つけることができます。

データベースの設定で何かをしなければならないと思いますが、あなたはその理論を裏付けるために十分な情報を提供していません。