huluwa12138 2017-06-05 08:15 采纳率: 0%
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jsp项目问题????????????

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.NullPointerException
com.dao.TeacherDao.CheckLogin(TeacherDao.java:19)
com.action.GoLogin.execute(GoLogin.java:65)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:446)
com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:285)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:238)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:238)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:252)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:544)
org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.13 logs.

package com.dao;

import com.db.DBHelper;

import com.bean.TeacherBean;

import java.util.*;

import java.sql.*;

public class TeacherDao {

//验证登录
public String CheckLogin(String username, String password){
    String id = null;
    String sql="select * from Teacher where Teacher_Username='"+username+"' and Teacher_Password='"+password+"'";
    Statement stat = null;
    ResultSet rs = null;
    Connection conn = new DBHelper().getConn();
    try{
        stat = conn.createStatement();
        rs = stat.executeQuery(sql);
        while (rs.next()) {
            id = rs.getString("Teacher_ID");
        }
    }
    catch(SQLException ex){}
    return id;
}
//验证密码
public boolean CheckPassword(String id, String password){
    boolean ps = false;
    String sql="select * from Teacher where Teacher_ID='"+id+"' and Teacher_Password='"+password+"'";
    Statement stat = null;
    ResultSet rs = null;
    Connection conn = new DBHelper().getConn();
    try{
        stat = conn.createStatement();
        rs = stat.executeQuery(sql);
        while (rs.next()) {
            ps=true;
        }
    }
    catch(SQLException ex){}
    return ps;
}
//获取列表
public List<TeacherBean> GetList(String strwhere,String strorder){
    String sql="select * from Teacher";
    if(!(isInvalid(strwhere)))
    {
        sql+=" where "+strwhere;
    }
    if(!(isInvalid(strorder)))
    {
        sql+=" order by "+strorder;
    }
    Statement stat = null;
    ResultSet rs = null;
    Connection conn = new DBHelper().getConn();
    List<TeacherBean> list=new ArrayList<TeacherBean>();
    try{
        stat = conn.createStatement();
        rs = stat.executeQuery(sql);
        while(rs.next()){
            TeacherBean cnbean=new TeacherBean();
            cnbean.setTeacher_ID(rs.getInt("Teacher_ID"));
            cnbean.setTeacher_Username(rs.getString("Teacher_Username"));
            cnbean.setTeacher_Password(rs.getString("Teacher_Password"));
            cnbean.setTeacher_Name(rs.getString("Teacher_Name"));
            cnbean.setTeacher_Sex(rs.getString("Teacher_Sex"));
            cnbean.setTeacher_Tel(rs.getString("Teacher_Tel"));
            list.add(cnbean);
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        try {
            if (conn != null)
                conn.close();
            if (stat != null)
                stat.close();
            if (rs != null)
                rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    return list;
}

//获取指定ID的实体Bean
public TeacherBean GetBean(int id){
    String sql="select * from Teacher where Teacher_ID="+id;
    Statement stat = null;
    ResultSet rs = null;
    Connection conn = new DBHelper().getConn();
    TeacherBean cnbean=new TeacherBean();
    try{
        stat = conn.createStatement();
        rs = stat.executeQuery(sql);
        while(rs.next()){
            cnbean.setTeacher_ID(rs.getInt("Teacher_ID"));
            cnbean.setTeacher_Username(rs.getString("Teacher_Username"));
            cnbean.setTeacher_Password(rs.getString("Teacher_Password"));
            cnbean.setTeacher_Name(rs.getString("Teacher_Name"));
            cnbean.setTeacher_Sex(rs.getString("Teacher_Sex"));
            cnbean.setTeacher_Tel(rs.getString("Teacher_Tel"));

        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        try {
            if (conn != null)
                conn.close();
            if (stat != null)
                stat.close();
            if (rs != null)
                rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    return cnbean;
}

//添加
public void Add(TeacherBean cnbean){
    String sql="insert into Teacher (";
    sql+="Teacher_Username,Teacher_Password,Teacher_Name,Teacher_Sex,Teacher_Tel";
    sql+=") values(";
    sql+="'"+cnbean.getTeacher_Username()+"','"+cnbean.getTeacher_Password()+"','"+cnbean.getTeacher_Name()+"','"+cnbean.getTeacher_Sex()+"','"+cnbean.getTeacher_Tel()+"'";
    sql+=")";
    Statement stat = null;
    ResultSet rs = null;
    Connection conn = new DBHelper().getConn();
    try{
        stat = conn.createStatement();
        stat.executeUpdate(sql);
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        try {
            if (conn != null)
                conn.close();
            if (stat != null)
                stat.close();
            if (rs != null)
                rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}
//修改
public void Update(TeacherBean cnbean){
    String sql="update Teacher set ";
    sql+="Teacher_Username='"+cnbean.getTeacher_Username()+"',";
    sql+="Teacher_Password='"+cnbean.getTeacher_Password()+"',";
    sql+="Teacher_Name='"+cnbean.getTeacher_Name()+"',";
    sql+="Teacher_Sex='"+cnbean.getTeacher_Sex()+"',";
    sql+="Teacher_Tel='"+cnbean.getTeacher_Tel()+"'";

    sql+=" where Teacher_ID='"+cnbean.getTeacher_ID()+"'";
    Statement stat = null;
    ResultSet rs = null;
    Connection conn = new DBHelper().getConn();
    try{
        stat = conn.createStatement();
        stat.executeUpdate(sql);
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        try {
            if (conn != null)
                conn.close();
            if (stat != null)
                stat.close();
            if (rs != null)
                rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}
//删除
public void Delete(String strwhere){
    String sql="delete Teacher where ";
    sql+=strwhere;
    Statement stat = null;
    ResultSet rs = null;
    Connection conn = new DBHelper().getConn();
    try{
        stat = conn.createStatement();
        stat.executeUpdate(sql);
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        try {
            if (conn != null)
                conn.close();
            if (stat != null)
                stat.close();
            if (rs != null)
                rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}


//判断是否空值
private boolean isInvalid(String value) {
    return (value == null || value.length() == 0);
}

//测试
public static void main(String[] args) {
    System.out.println("");
}

}

  • 写回答

2条回答 默认 最新

  • 全栈极简 博客专家认证 2017-06-05 08:26
    关注

    java.lang.NullPointerException
    com.dao.TeacherDao.CheckLogin(TeacherDao.java:19)

    TeacherDao.java:19 有对象为null.

    评论

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