struts初学报错

LoginAction.java:package wu.struts;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;public class LoginAction extends Action { @Override
public ActionForward execute(ActionMapping mapping, ActionForm form,

HttpServletRequest request, HttpServletResponse response)

throws Exception {

LoginForm loginForm=(LoginForm)form;


if(loginForm.getName().equals("itcast")){

return mapping.findForward("loginSuccess");

}
else{

return mapping.findForward("loginFailure");
}
}}LoginForm.java:package wu.struts;import org.apache.struts.action.ActionForm;public class LoginForm extends ActionForm {
private static final long serialVersionUID = 1L; private String name=null;

private String password=null;

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}}struts-config.xml:
<struts-config>
<form-beans>
<form-bean name="loginForm" type="wu.struts.LoginForm"/>
</form-beans>
<action-mappings>
<action path="/login" type="wu.struts.LoginAction" name="loginForm">
<forward name="loginSuccess" path="/LoginSuccess.jsp"></forward>
<forward name="loginFailure" path="/LoginFailure.jsp"></forward>
</action>
</action-mappings></struts-config>
web.xml:
<servlet>
  <servlet-name>action</servlet-name>
  <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
  <init-param>
  <param-name>config</param-name>
  <param-value>/WEB-INF/struts-config.xml</param-value>
  </init-param>
  <load-on-startup>0</load-on-startup>
  </servlet>
 
  <servlet-mapping>
  <servlet-name>action</servlet-name>
<url-pattern>*.do</url-pattern>
  </servlet-mapping>
</servlet>
Login.jsp:
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<html>
  <body>
   
<form action="<%=request.getContextPath() %>/login.do"  method= "post">
username:<input type="text" name="username"><br>
password:<input type="password" name="password"><br/>
<input type="submit" value="login">

</form>
  </body>
</html>LoginSuccess.jsp:
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<html>
  <body>
    LoginSuccess <br>
  </body>
</html>LoginFailure.jsp:
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<html>
  <body>
    LoginFailure <br>
  </body>
</html>错误信息：
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception javax.servlet.ServletException: java.lang.NullPointerException
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:286)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause java.lang.NullPointerException
wu.struts.LoginAction.execute(LoginAction.java:23)
org.apache.struts.chain.commands.servlet.ExecuteAction.execute(ExecuteAction.java:58)
org.apache.struts.chain.commands.AbstractExecuteAction.execute(AbstractExecuteAction.java:67)
org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.13 logs.

解决方案 »

  1.   

    java.lang.NullPointerException
    空指针异常  
    (LoginAction.java:23)
    23行值没得到
    struts1木用过
      

  2.   

    java.lang.NullPointerException
    wu.struts.LoginAction.execute(LoginAction.java:23)估计是你loginForm.getName()这个值为空吧。 
      

  3.   

    jsp页面的变量是否跟formbean中的name名一致，其他倒是没看出来错误
      

  4.   

    你在LoginForm里面定义的是name，而你在Login.jsp里面写的input属性name是username，这两个属性必须是一样的，后台的LoginForm才能取到值。应该这么写：//LoginForm
    private String username="";
    private String password="";
    jsp页面<form action="..." method="POST">
    <input type="text" name="username"/>
    <input type="password" name="password"/>
    <input type="submit" value="提交"/>
    </form>
      

  5.   


    对头，页面中传递的name的名称必须与actionform中 的属性的一致，不然，它木有办法进行填充..导致的结果是在action中取不到actionform，就报了空指针了。
      

  6.   

    5楼正解，form和前台页面的field必须一致