Question

Struts2的Action使用validate（）方法，提示空指针错误！

我建有Tuser.java、
package com.struts2.pojo;

public class Tuser {
private int id;
private String name;
private String password;
private String ds;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
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;
}
public void setDs(String ds) {
this.ds = ds;
}
public String getDs() {
return ds;
}
}

但是：LoginAction.java
public class LoginAction extends ActionSupport {

/**
*
*/
private static final long serialVersionUID = 1L;
private TuserService tuserService;
private Tuser tuser;

public TuserService getTuserService() {
return tuserService;
}
public void setTuserService(TuserService tuserService) {
this.tuserService = tuserService;
}
public Tuser getTuser() {
return tuser;
}
public void setTuser(Tuser tuser) {
this.tuser = tuser;
}

public String execute() throws Exception {

if("hello".equals(this.tuser.getName().trim())&&"word".equals(this.tuser.getPassword().trim())){
return SUCCESS;
}
else{
this.addFieldError("name", "用户名或者密码错误！");
return ERROR;
}
}

public void validate(){

if(this.tuser.getName() == null||"".equals(this.tuser.getName().trim())){
this.addFieldError("name", "请输入用户名");
}

if(this.tuser.getPassword() == null ||"".equals(this.tuser.getPassword().trim())){
this.addFieldError("password", "请输入密码");
}

}

}

运行时，MyEclipse不报错误，只是网页显示如下错误：

exception

java.lang.NullPointerException
com.struts.action.LoginAction.validate(LoginAction.java:46)
com.opensymphony.xwork2.validator.ValidationInterceptor.doBeforeInvocat
。。。。。。。。。。。。。。。。。。。。。。。。。

取不到值，范例是在Action写Tuser的getter和setter方法，我是import进来的！有问题吗?

Answer 1

对，是你的tuser对象没有实例化；所以tuser.getName() 时，报异常！

Answer 2

tuser没有初始化

Answer 3

在你的jsp表单里：比如说你要提交name要写成 <s:textfield name="tuser.name" size="20"/>