java web从零单排第十二期《struts2》数据校验显示出错信息
熟悉servlet编程处理错误信息显示到JSP页面时，都会将错误信息保存到request中，然后在JSP页面中通过JSTL/EL表达式显示出来，而struts2也是使用这种方式，但是封装的更加完善。
1.在JSP页面中加入调试标签：
加入调试标签后的JSP页面register.jsp代码如下：
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri="/struts-tags" prefix="s" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<body>
<s:debug></s:debug>
<s:form action="register" method="post">
账号<s:textfield name="username" ></s:textfield>${errors.username[0]}
<br>
密码<s:textfield name="password" ></s:textfield>${errors.password[0]}
<br>
年龄<s:textfield name="age"></s:textfield>${errors.age[0]}
<br>
身高<s:textfield name="height"></s:textfield>${errors.height[0]}
<br>
<s:submit value="提交"></s:submit>
</s:form>
</body>
</html>
2.新建Register.java
package controller;
import com.opensymphony.xwork2.ActionSupport;
public class Register extends ActionSupport{
private String username;
private String password;
private Integer age;
private Double height;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Double getHeight() {
return height;
}
public void setHeight(Double height) {
this.height = height;
}
@Override
public void validate() {
// TODO Auto-generated method stub
if(!username.equals("niujiabin"))
{
this.addFieldError("username", "用户名非法，必须为niujiabin");
}
if(!password.equals("jiabinniu"))
{
this.addFieldError("password", "密码非法，必须为jiabinniu");
}
if(age==null||age>=120||age<0)
{
this.addFieldError("age", "年龄非法，必须在0-120之间");
}
if(height==null||height<0||height>3)
{
this.addFieldError("height", "身高非法，必须在0-3米之间");
}
}
@Override
public String execute() throws Exception {
// TODO Auto-generated method stub
return "register";
}
}
3.配置文件struts.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" "http://struts.apache.org/dtd/struts-2.0.dtd">
<struts>
<package name="Maybe" extends="struts-default">
<action name="register" class="controller.Register">
<result name="register">/showregister.jsp</result>
<result name="input">/register.jsp</result>
</action>
</package>
<constant name="struts.ui.theme" value="simple"></constant>
</struts>
4.运行后点击debug：
在值栈中可以看到错误信息的存在，它的存储形式为Map形式，所以在jsp页面添加EL表达式从request去出错误信息显示在jsp页面上。
5.点击提交按钮：
6.显示全局出错信息修改Register.java:
package controller;
import com.opensymphony.xwork2.ActionSupport;
public class Register extends ActionSupport{
private String username;
private String password;
private Integer age;
private Double height;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Double getHeight() {
return height;
}
public void setHeight(Double height) {
this.height = height;
}
@Override
public void validate() {
// TODO Auto-generated method stub
if(!username.equals("niujiabin"))
{
this.addActionError("用户名非法，必须为niujiabin");
}
if(!password.equals("jiabinniu"))
{
this.addActionError("密码非法，必须为jiabinniu");
}
if(age==null||age>=120||age<0)
{
this.addActionError("年龄非法，必须在0-120之间");
}
if(height==null||height<0||height>3)
{
this.addActionError("身高非法，必须在0-3米之间");
}
}
@Override
public String execute() throws Exception {
// TODO Auto-generated method stub
return "register";
}
}
调用ActionListener方法来显示错误信息。
7.修改register.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri="/struts-tags" prefix="s" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<body>
<s:actionerror/>
<br>
<s:form action="register" method="post">
账号<s:textfield name="username" ></s:textfield>
<br>
密码<s:textfield name="password" ></s:textfield>
<br>
年龄<s:textfield name="age"></s:textfield>
<br>
身高<s:textfield name="height"></s:textfield>
<br>
<s:submit value="提交"></s:submit>
</s:form>
</body>
</html>
注意：actionerror标签。
8.运行程序，点击提交按钮：
9.addFieldError和addActionError的对比
首先看一下源代码：
/*
* Copyright 2002-2007,2009 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.opensymphony.xwork2;
import java.util.Collection;
import java.util.List;
import java.util.Map;
/**
* ValidationAware classes can accept Action (class level) or field level error messages. Action level messages are kept
* in a Collection. Field level error messages are kept in a Map from String field name to a List of field error msgs.
*
* @author plightbo
*/
public interface ValidationAware {
/**
* Set the Collection of Action-level String error messages.
*
* @param errorMessages Collection of String error messages
*/
void setActionErrors(Collection<String> errorMessages);
/**
* Get the Collection of Action-level error messages for this action. Error messages should not
* be added directly here, as implementations are free to return a new Collection or an
* Unmodifiable Collection.
*
* @return Collection of String error messages
*/
Collection<String> getActionErrors();
/**
* Set the Collection of Action-level String messages (not errors).
*
* @param messages Collection of String messages (not errors).
*/
void setActionMessages(Collection<String> messages);
/**
* Get the Collection of Action-level messages for this action. Messages should not be added
* directly here, as implementations are free to return a new Collection or an Unmodifiable
* Collection.
*
* @return Collection of String messages
*/
Collection<String> getActionMessages();
/**
* Set the field error map of fieldname (String) to Collection of String error messages.
*
* @param errorMap field error map
*/
void setFieldErrors(Map<String, List<String>> errorMap);
/**
* Get the field specific errors associated with this action. Error messages should not be added
* directly here, as implementations are free to return a new Collection or an Unmodifiable
* Collection.
*
* @return Map with errors mapped from fieldname (String) to Collection of String error messages
*/
Map<String, List<String>> getFieldErrors();
/**
* Add an Action-level error message to this Action.
*
* @param anErrorMessage the error message
*/
void addActionError(String anErrorMessage);
/**
* Add an Action-level message to this Action.
*
* @param aMessage the message
*/
void addActionMessage(String aMessage);
/**
* Add an error message for a given field.
*
* @param fieldName name of field
* @param errorMessage the error message
*/
void addFieldError(String fieldName, String errorMessage);
/**
* Check whether there are any Action-level error messages.
*
* @return true if any Action-level error messages have been registered
*/
boolean hasActionErrors();
/**
* Checks whether there are any Action-level messages.
*
* @return true if any Action-level messages have been registered
*/
boolean hasActionMessages();
/**
* Checks whether there are any action errors or field errors.
* <p/>
* <b>Note</b>: that this does not have the same meaning as in WW 1.x.
*
* @return <code>(hasActionErrors() || hasFieldErrors())</code>
*/
boolean hasErrors();
/**
* Check whether there are any field errors associated with this action.
*
* @return whether there are any field errors
*/
boolean hasFieldErrors();
}
从定义中就可以看出，actionError是Collection的方式进行存储的，而fieldError是以Map进行存储的。
10.小结：
这节本身没有什么难度，通过这一节希望大家养成多看源代码的习惯，能让自己有非常的提升。