开始是一个登录界面,每次点击登录进入的下一个界面会如下所示的东西。中间一段是我的代码。出现这种现象的原因是什么,望高手指点下。初学jsp还有很多的盲点
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: An exception occurred processing JSP page /Untitled-4.jsp at line 1512: String name=request.getParameter("name");
13: String password=request.getParameter("password");
14: //判断用户名和密码是否正确
15: if(name.equals("jiaoshi") && password.equals("123")){
16: %>
17: <!--jsp:forward指令完成转发动作-->
18: <jsp:forward page="Untitled-5.jsp">
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:519)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:428)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
root cause java.lang.NullPointerException
org.apache.jsp.Untitled_002d4_jsp._jspService(Untitled_002d4_jsp.java:69)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:386)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.32 logs.
--------------------------------------------------------------------------------Apache Tomcat/6.0.32
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: An exception occurred processing JSP page /Untitled-4.jsp at line 1512: String name=request.getParameter("name");
13: String password=request.getParameter("password");
14: //判断用户名和密码是否正确
15: if(name.equals("jiaoshi") && password.equals("123")){
16: %>
17: <!--jsp:forward指令完成转发动作-->
18: <jsp:forward page="Untitled-5.jsp">
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:519)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:428)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
root cause java.lang.NullPointerException
org.apache.jsp.Untitled_002d4_jsp._jspService(Untitled_002d4_jsp.java:69)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:386)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.32 logs.
--------------------------------------------------------------------------------Apache Tomcat/6.0.32
java.lang.NullPointerException
空指针错误
JAVA所有的引用,都可以认为是指针
// 如果 name==null 或者 password==null, 调用 name.equals 或者 password.equals 就会出现空指针异常
if(name.equals("jiaoshi") && password.equals("123")){
// ...
}// 建议改为
if("jiaoshi".equals(name) && "123".equals(password)) {
// ...
}