struts2中ActionSupport类具有验证表单的功能，可以将一些错误信息显示在jsp页面上。
ActionSupport的父类是Object，实现了六个接口，分别是：Action，LocalProvider，TextProvider，Validateble，ValidateAware，Serializable。
由于ActionSupport类实现了Action接口，可以确定ActionSupport拥有Action的5个常量值，在此基础上ActionSupport对功能进行了许多拓展，如具有验证功能。
我们先找一下validateble接口，点开Web App libraries 下的 xwork-core jar包
双击之后把源代码添加进去：
代码如下：
/*
* Copyright 2002-2006,2009 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 com.opensymphony.xwork2.inject.Container;
import com.opensymphony.xwork2.inject.Inject;
import com.opensymphony.xwork2.util.ValueStack;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.ResourceBundle;
/**
* Provides a default implementation for the most common actions.
* See the documentation for all the interfaces this class implements for more detailed information.
*/
public class ActionSupport implements Action, Validateable, ValidationAware, TextProvider, LocaleProvider, Serializable {
protected static Logger LOG = LoggerFactory.getLogger(ActionSupport.class);
private final ValidationAwareSupport validationAware = new ValidationAwareSupport();
private transient TextProvider textProvider;
private Container container;
public void setActionErrors(Collection<String> errorMessages) {
validationAware.setActionErrors(errorMessages);
}
public Collection<String> getActionErrors() {
return validationAware.getActionErrors();
}
public void setActionMessages(Collection<String> messages) {
validationAware.setActionMessages(messages);
}
public Collection<String> getActionMessages() {
return validationAware.getActionMessages();
}
/**
* @deprecated Use {@link #getActionErrors()}.
*/
@Deprecated
public Collection<String> getErrorMessages() {
return getActionErrors();
}
/**
* @deprecated Use {@link #getFieldErrors()}.
*/
@Deprecated
public Map<String, List<String>> getErrors() {
return getFieldErrors();
}
public void setFieldErrors(Map<String, List<String>> errorMap) {
validationAware.setFieldErrors(errorMap);
}
public Map<String, List<String>> getFieldErrors() {
return validationAware.getFieldErrors();
}
public Locale getLocale() {
ActionContext ctx = ActionContext.getContext();
if (ctx != null) {
return ctx.getLocale();
} else {
if (LOG.isDebugEnabled()) {
LOG.debug("Action context not initialized");
}
return null;
}
}
public boolean hasKey(String key) {
return getTextProvider().hasKey(key);
}
public String getText(String aTextName) {
return getTextProvider().getText(aTextName);
}
public String getText(String aTextName, String defaultValue) {
return getTextProvider().getText(aTextName, defaultValue);
}
public String getText(String aTextName, String defaultValue, String obj) {
return getTextProvider().getText(aTextName, defaultValue, obj);
}
public String getText(String aTextName, List<?> args) {
return getTextProvider().getText(aTextName, args);
}
public String getText(String key, String[] args) {
return getTextProvider().getText(key, args);
}
public String getText(String aTextName, String defaultValue, List<?> args) {
return getTextProvider().getText(aTextName, defaultValue, args);
}
public String getText(String key, String defaultValue, String[] args) {
return getTextProvider().getText(key, defaultValue, args);
}
public String getText(String key, String defaultValue, List<?> args, ValueStack stack) {
return getTextProvider().getText(key, defaultValue, args, stack);
}
public String getText(String key, String defaultValue, String[] args, ValueStack stack) {
return getTextProvider().getText(key, defaultValue, args, stack);
}
/**
* Dedicated method to support I10N and conversion errors
*
* @param key message which contains formatting string
* @param expr that should be formatted
* @return formatted expr with format specified by key
*/
public String getFormatted(String key, String expr) {
Map<String, Object> conversionErrors = ActionContext.getContext().getConversionErrors();
if (conversionErrors.containsKey(expr)) {
String[] vals = (String[]) conversionErrors.get(expr);
return vals[0];
} else {
final ValueStack valueStack = ActionContext.getContext().getValueStack();
final Object val = valueStack.findValue(expr);
return getText(key, Arrays.asList(val));
}
}
public ResourceBundle getTexts() {
return getTextProvider().getTexts();
}
public ResourceBundle getTexts(String aBundleName) {
return getTextProvider().getTexts(aBundleName);
}
public void addActionError(String anErrorMessage) {
validationAware.addActionError(anErrorMessage);
}
public void addActionMessage(String aMessage) {
validationAware.addActionMessage(aMessage);
}
public void addFieldError(String fieldName, String errorMessage) {
validationAware.addFieldError(fieldName, errorMessage);
}
public String input() throws Exception {
return INPUT;
}
public String doDefault() throws Exception {
return SUCCESS;
}
/**
* A default implementation that does nothing an returns "success".
* <p/>
* Subclasses should override this method to provide their business logic.
* <p/>
* See also {@link com.opensymphony.xwork2.Action#execute()}.
*
* @return returns {@link #SUCCESS}
* @throws Exception can be thrown by subclasses.
*/
public String execute() throws Exception {
return SUCCESS;
}
public boolean hasActionErrors() {
return validationAware.hasActionErrors();
}
public boolean hasActionMessages() {
return validationAware.hasActionMessages();
}
public boolean hasErrors() {
return validationAware.hasErrors();
}
public boolean hasFieldErrors() {
return validationAware.hasFieldErrors();
}
/**
* Clears field errors. Useful for Continuations and other situations
* where you might want to clear parts of the state on the same action.
*/
public void clearFieldErrors() {
validationAware.clearFieldErrors();
}
/**
* Clears action errors. Useful for Continuations and other situations
* where you might want to clear parts of the state on the same action.
*/
public void clearActionErrors() {
validationAware.clearActionErrors();
}
/**
* Clears messages. Useful for Continuations and other situations
* where you might want to clear parts of the state on the same action.
*/
public void clearMessages() {
validationAware.clearMessages();
}
/**
* Clears all errors. Useful for Continuations and other situations
* where you might want to clear parts of the state on the same action.
*/
public void clearErrors() {
validationAware.clearErrors();
}
/**
* Clears all errors and messages. Useful for Continuations and other situations
* where you might want to clear parts of the state on the same action.
*/
public void clearErrorsAndMessages() {
validationAware.clearErrorsAndMessages();
}
/**
* A default implementation that validates nothing.
* Subclasses should override this method to provide validations.
*/
public void validate() {
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
/**
* <!-- START SNIPPET: pause-method -->
* Stops the action invocation immediately (by throwing a PauseException) and causes the action invocation to return
* the specified result, such as {@link #SUCCESS}, {@link #INPUT}, etc.
* <p/>
* <p/>
* The next time this action is invoked (and using the same continuation ID), the method will resume immediately
* after where this method was called, with the entire call stack in the execute method restored.
* <p/>
* <p/>
* Note: this method can <b>only</b> be called within the {@link #execute()} method.
* <!-- END SNIPPET: pause-method -->
*
* @param result the result to return - the same type of return value in the {@link #execute()} method.
*/
public void pause(String result) {
}
/**
* If called first time it will create {@link com.opensymphony.xwork2.TextProviderFactory},
* inject dependency (if {@link com.opensymphony.xwork2.inject.Container} is accesible) into in,
* then will create new {@link com.opensymphony.xwork2.TextProvider} and store it in a field
* for future references and at the returns reference to that field
*
* @return reference to field with TextProvider
*/
private TextProvider getTextProvider() {
if (textProvider == null) {
TextProviderFactory tpf = new TextProviderFactory();
if (container != null) {
container.inject(tpf);
}
textProvider = tpf.createInstance(getClass(), this);
}
return textProvider;
}
@Inject
public void setContainer(Container container) {
this.container = container;
}
}
Validateable接口只有一个方法，即validate(),必须覆盖该方法来实现自定义的验证功能。
下面将实现继承自ActionSupport类的实例，是action控制层具有验证功能。
将上一节中的Login.java添加validate方法，具体代码如下：
package controller;
import com.opensymphony.xwork2.ActionSupport;
public class Login extends ActionSupport{
private String username;
public String getUsername() {
return username;
}
public void setUsername(String username) {
System.out.println("username setting");
this.username = username;
}
public void setPassword(String password) {
System.out.println("password setting");
this.password = password;
}
public String getPassword() {
return password;
}
private String password;
@Override
public void validate() {
// TODO Auto-generated method stub
super.validate();
if("".equals(this.getUsername()))
{
this.addFieldError("usernname", "用户名不能为空");
}
if("".equals(this.getPassword()))
{
this.addFieldError("password", "密码不能为空");
}
}
public String execute()
{
if(username.equals("hello")&&password.equals("struts2"))
{
return "success";
}
else
{
return "false";
}
}
}
validate方法是在execute方法之前执行的。
如果表单的内容为空，则执行this.addFieldError()方法：
this.addFieldError("usernname", "用户名不能为空");
this.addFieldError("password", "密码不能为空");
将出错的信息显示在jsp页面名称为username和password的s:textfield标签中，然后就可以查看login.jsp页面的变化：
<%@ 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> <form action="login.action" method="post" name="login"> <s:textfield name="username" label="账号"></s:textfield> <s:textfield name=password“" label="密码"></s:textfield> <br> <s:submit value="提交"></s:submit> </form> </body> </html>
在新的jsp页面中使用了struts2表单标签库，s:textfield是在浏览器显示单行文本域，而s:textfield name的属性值一定要和Login.java类中的属性名相同，这样才可以上实现自动填充，label属性是标签内的文本提示内容。
最后还需要配置struts.xml文件，并显示错误提示，等待重新输入：
<?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="login" class="controller.Login">
<result name="success">/true.jsp</result>
<result name="false">/false.jsp</result>
<result name="input">/login.jsp</result>
</action>
</package>
</struts>
其中result name=“inout”是当出现错误自动转到重新输入的状态。
我们来查看一下Action这个类：
/*
* 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;
/**
* All actions <b>may</b> implement this interface, which exposes the <code>execute()</code> method.
* <p/>
* However, as of XWork 1.1, this is <b>not</b> required and is only here to assist users. You are free to create POJOs
* that honor the same contract defined by this interface without actually implementing the interface.
*/
public interface Action {
/**
* The action execution was successful. Show result
* view to the end user.
*/
public static final String SUCCESS = "success";
/**
* The action execution was successful but do not
* show a view. This is useful for actions that are
* handling the view in another fashion like redirect.
*/
public static final String NONE = "none";
/**
* The action execution was a failure.
* Show an error view, possibly asking the
* user to retry entering data.
*/
public static final String ERROR = "error";
/**
* The action execution require more input
* in order to succeed.
* This result is typically used if a form
* handling action has been executed so as
* to provide defaults for a form. The
* form associated with the handler should be
* shown to the end user.
* <p/>
* This result is also used if the given input
* params are invalid, meaning the user
* should try providing input again.
*/
public static final String INPUT = "input";
/**
* The action could not execute, since the
* user most was not logged in. The login view
* should be shown.
*/
public static final String LOGIN = "login";
/**
* Where the logic of the action is executed.
*
* @return a string representing the logical result of the execution.
* See constants in this interface for a list of standard result values.
* @throws Exception thrown if a system level exception occurs.
* <b>Note:</b> Application level exceptions should be handled by returning
* an error value, such as <code>Action.ERROR</code>.
*/
public String execute() throws Exception;
}
可以看到在Action中定义了许多常量字符串INPUT就是其中之一，如果运行了Login.java中的validate方法，addFieldError方法就会返回到login.jsp页面，显示出错误信息。
运行一下，若不输入用户名和密码，运行结果如图所示：
