java web从零单排第七期《struts2》用ActionSupport类验证提交表单

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;@Overridepublic void validate() {// TODO Auto-generated method stubsuper.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：