package mychat;
import java.sql.*;
import java.io.*;
import javax.servlet.*;
import java.util.*;
import javax.servlet.http.*;public class GetServlet extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
String xml = null;
String rnd = request.getParameter("rnd");
DB myDB=new DB();
String sql = "select * from tb_userinfo where UserNumber in( select FriendNumber from tb_friends where UserNumber='11111')";
try {
ResultSet rs = myDB.executeQuery(sql);//数据结果
StringBuffer buf = new StringBuffer();
buf.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
buf.append("<userlist>");
while (rs.next())
{
buf.append("<userinfo>");
buf.append("<username>" + rs.getString("UserName") +"</username>");
buf.append("<usernumber>" + rs.getString("UserNumber") + "</usernumber>");
buf.append("<userstate>" + rs.getString("UserState") + "</userstate>");
buf.append("</userinfo>");
} buf.append("</userlist>");
xml=buf.toString();
response.setContentType("text/xml;charset=UTF-8");
//设置返回数据类型为xml格式,编码为utf8
java.io.PrintWriter out = response.getWriter();
System.out.println(xml);
out.print(xml);
}
catch (SQLException e) {
e.printStackTrace();
}
myDB.close();
}public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
doPost(request, response);
}}exception java.lang.NullPointerException
mychat.GetServlet.doGet(GetServlet.java:24)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)原本运行的好好的,后来突然就出现这个错误了,不知道为什么啊~源程序什么都没有改动的。
高手来帮帮忙啊~
import java.sql.*;
import java.io.*;
import javax.servlet.*;
import java.util.*;
import javax.servlet.http.*;public class GetServlet extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
String xml = null;
String rnd = request.getParameter("rnd");
DB myDB=new DB();
String sql = "select * from tb_userinfo where UserNumber in( select FriendNumber from tb_friends where UserNumber='11111')";
try {
ResultSet rs = myDB.executeQuery(sql);//数据结果
StringBuffer buf = new StringBuffer();
buf.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
buf.append("<userlist>");
while (rs.next())
{
buf.append("<userinfo>");
buf.append("<username>" + rs.getString("UserName") +"</username>");
buf.append("<usernumber>" + rs.getString("UserNumber") + "</usernumber>");
buf.append("<userstate>" + rs.getString("UserState") + "</userstate>");
buf.append("</userinfo>");
} buf.append("</userlist>");
xml=buf.toString();
response.setContentType("text/xml;charset=UTF-8");
//设置返回数据类型为xml格式,编码为utf8
java.io.PrintWriter out = response.getWriter();
System.out.println(xml);
out.print(xml);
}
catch (SQLException e) {
e.printStackTrace();
}
myDB.close();
}public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
doPost(request, response);
}}exception java.lang.NullPointerException
mychat.GetServlet.doGet(GetServlet.java:24)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)原本运行的好好的,后来突然就出现这个错误了,不知道为什么啊~源程序什么都没有改动的。
高手来帮帮忙啊~
mychat.GetServlet.doGet(GetServlet.java:24)
是空指针异常,是否你的doGet方法有问题呀?也查一下你的数据库的结果集是否为空。