菜鸟求助啊 HTTP Status 500 - java.lang.NullPointerException

2013-06-12 02:07:07 726 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

java.lang.NullPointerException出现的几种原因及解决方案 java.lang.NullPointerException（空指针异常）是Java开发中常见错误，多因对null对象执行操作所致。常见原因包括：调用null对象的方法或属性、将null作为数组访问、null参与自动拆箱、集合未初始化就操作等。解决方案涵盖：调用前判空（如if语句、Objects.requireNonNull）、初始化对象与集合、使用Optional类规避风险、借助IDE调试定位null源头等。掌握其成因与解决办法，能有效提升代码健壮性，减少程序崩溃隐患，是Java开发者必备技能。阅读详情

2013-6-12 14:03:47 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet [jsp] in context with path [/Work] threw exception [java.lang.NullPointerException] with root cause
java.lang.NullPointerException
at org.apache.jsp.searchResult_jsp._jspService(searchResult_jsp.java:107)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
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)

求各位大大帮忙啊折腾好久了T_T

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a_9_5_2_7 2013-06-12

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今天刚遇到这个问题也是弄了好久才解决的刚开始以为是文件路径写错了, 查了半天结果是连接数据库的 connection还没有用完就关闭了,完美解决 ,仔细检查一下代码是不是什么东西没有用完就关闭了,希望对楼主有帮助;

ai276542486 2013-06-12

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哪个页面调用哪个servlet的时候出的问题呢。。

s6624773 2013-06-12

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package servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import com.DBUtil.DBCon; import com.javabean.Searchbean; import java.sql.*; public class SearchServlet extends HttpServlet { /** * Constructor of the object. */ public SearchServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); out.print(" This is "); out.print(this.getClass()); out.println(", using the GET method"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); String searchName = request.getParameter("result"); System.out.println(searchName); Searchbean sb = new Searchbean(); DBCon dbc =new DBCon(); Connection conn =dbc.getConn(); Statement stmt =dbc.getStmt(conn); ResultSet rs = dbc.getResultset(stmt, "select * from [movie] where name = '"+searchName+"'"); try { while(rs.next()){ String name= rs.getString("name"); sb.setStrname(rs.getString("name")); sb.setDirector(rs.getString("director")); sb.setActor(rs.getString("actor")); sb.setLanguage(rs.getString("language")); sb.setDictrict(rs.getString("distric")); sb.setDate(rs.getString("date")); sb.setImage(rs.getString("url")); System.out.println(name); System.out.println("数据读取成功"); session.setAttribute("sb",sb ); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } response.sendRedirect("searchResult.jsp"); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }

s6624773 2013-06-12