SSH结构的Form中代码写法问题。

SSH结构中的一个bean的代码(JbxxXzsm.java),分别对应数据库中的每个字段
public class JbxxXzsm implements java.io.Serializable {private String xzsmmc;
...
public String getXzsmmc() {
return this.xzsmmc;
}
public void setXzsmmc(String xzsmmc) {
this.xzsmmc = xzsmmc;
}
......JbxxXzsmForm，Form中的代码：
   private JbxxXzsm xzsm;    public JbxxXzsm getXzsm() {
        return xzsm;
    }    public void setXzsm(JbxxXzsm xzsm) {
        this.xzsm = xzsm;
    }

    public XzsmForm()
    {
        super();
        xzsm = new JbxxXzsm();
    }然后在Action中,xzsmForm.getXzsm()就直接取得Form中(对应jsp页面中文本框之类表单元素)的值了
        XzsmForm xzsmForm = (XzsmForm) form;
       JbxxXzsm xzsm = xzsmForm.getXzsm();请问JbxxXzsmForm中的代码是怎么工作的?为什么不象bean中一样用set,get封装页面每个文本框之类的表单元素?

解决方案 »

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LZ看看源码吧理解可能更深些
package org.apache.struts.action;
import org.apache.struts.upload.MultipartRequestHandler;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import java.io.Serializable;
public abstract class ActionForm implements Serializable {
 // ----------------------------------------------------- Instance Variables
 /**
 * The servlet instance to which we are attached.
 */
 protected transient ActionServlet servlet = null;
 /**
 * The MultipartRequestHandler for this form, can be
 * <code>null</code>.
 */
 protected transient MultipartRequestHandler multipartRequestHandler;
 /**
 * Return the servlet instance to which we are attached.
 *
 * @return The servlet instance to which we are attached.
 */
 protected ActionServlet getServlet() {
 return (this.servlet);
 }
 /**
 * Return the controller servlet instance to which we are attached. as
 * an <code>ActionServletWrapper</code>.
 *
 * @return An instance of {@link ActionServletWrapper}
 * @see ActionServletWrapper
 * @since Struts 1.0.1
 */
 public ActionServletWrapper getServletWrapper() {
 return new ActionServletWrapper(getServlet());
 }
 /**
 * Return the <code>MultipartRequestHandler</code> for this form The
 * reasoning behind this is to give form bean developers control over the
 * lifecycle of their multipart requests through the use of the
 * <code>finish</code> and/or <code>rollback</code> methods of
 * <code>MultipartRequestHandler</code>. This method will return
 * <code>null</code> if this form's enctype is not "multipart/form-data".
 * *
 * @return The {@link org.apache.struts.upload.MultipartRequestHandler}
 * for this form.
 * @see org.apache.struts.upload.MultipartRequestHandler
 */
 public MultipartRequestHandler getMultipartRequestHandler() {
 return multipartRequestHandler;
 }
 /**
 * Set the servlet instance to which we are attached (if
 * <code>servlet</code> is non-null).
 *
 * @param servlet The new controller servlet, if any
 */
 public void setServlet(ActionServlet servlet) {
 this.servlet = servlet;
 // :FIXME: Should this be releasing resources?
 }
 /**
 * Set the Handler provided for use in dealing with file uploads.
 *
 * @param multipartRequestHandler The Handler to use for fileuploads.
 */
 public void setMultipartRequestHandler(
 MultipartRequestHandler multipartRequestHandler) {
 this.multipartRequestHandler = multipartRequestHandler;
 }
 // --------------------------------------------------------- Public Methods
 /**
 * >Can be used to reset all bean properties to their default state.
 * This method is called before the properties are repopulated by the
 * controller.
 *
 * The default implementation attempts to forward to the HTTP version
 * of this method.
 *
 * @param mapping The mapping used to select this instance
 * @param request The servlet request we are processing
 */
 public void reset(ActionMapping mapping, ServletRequest request) {
 try {
 reset(mapping, (HttpServletRequest) request);
 } catch (ClassCastException e) {
 ; // FIXME: Why would this ever happen except a null
 }
 }
 /**
 * Can be used to reset bean properties to their default state, as
 * needed. This method is called before the properties are repopulated by
 * the controller.
 *
 * The default implementation does nothing. In practice, the only
 * properties that need to be reset are those which represent checkboxes
 * on a session-scoped form. Otherwise, properties can be given initial
 * values where the field is declared. 
 *
 * If the form is stored in session-scope so that values can be
 * collected over multiple requests (a "wizard"), you must be very careful
 * of which properties, if any, are reset. As mentioned, session-scope
 * checkboxes must be reset to false for any page where this property is
 * set. This is because the client does not submit a checkbox value when
 * it is clear (false). If a session-scoped checkbox is not proactively
 * reset, it can never be set to false.
 *
 * This method is not the appropriate place to
 * initialize form value for an "update" type page (this should be done in
 * a setup Action). You mainly need to worry about setting checkbox values
 * to false; most of the time you can leave this method unimplemented.
 * 
 *
 * @param mapping The mapping used to select this instance
 * @param request The servlet request we are processing
 */
 public void reset(ActionMapping mapping, HttpServletRequest request) {
 // Default implementation does nothing
 }
 /**
 * Can be used to validate the properties that have been set for this
 * non-HTTP request, and return an <code>ActionErrors</code> object that
 * encapsulates any validation errors that have been found. If no errors
 * are found, return <code>null</code> or an <code>ActionErrors</code>
 * object with no recorded error messages.
 *
 * The default implementation attempts to forward to the HTTP version
 * of this method.
 *
 * @param mapping The mapping used to select this instance
 * @param request The servlet request we are processing
 * @return The set of validation errors, if validation failed; an empty
 * set or <code>null</code> if validation succeeded.
 */
 public ActionErrors validate(ActionMapping mapping, ServletRequest request) {
 try {
 return (validate(mapping, (HttpServletRequest) request));
 } catch (ClassCastException e) {
 return (null);
 }
 }
 /
 * The default implementation performs no validation and returns
 * <code>null</code>. Subclasses must override this method to provide any
 * validation they wish to perform.
 *
 * @param mapping The mapping used to select this instance
 * @param request The servlet request we are processing
 * @return The set of validation errors, if validation failed; an empty
 * set or <code>null</code> if validation succeeded.
 * @see DynaActionForm
 */
 public ActionErrors validate(ActionMapping mapping,
 HttpServletRequest request) {
 return (null);
 }
LZ看看源码吧理解可能更深些/*
* $Id: ActionForm.java 471754 2006-11-06 14:55:09Z husted $
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.struts.action;import org.apache.struts.upload.MultipartRequestHandler;import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;import java.io.Serializable;/**
* An ActionForm is a JavaBean optionally associated with
* one or more <code>ActionMappings</code>. Such a bean will have had its
* properties initialized from the corresponding request parameters before the
* corresponding <code>Action.execute</code> method is called.
*
* When the properties of this bean have been populated, but before the
* <code>execute</code> method of the <code>Action</code> is called, this
* bean's <code>validate</code> method will be called, which gives the bean a
* chance to verify that the properties submitted by the user are correct and
* valid. If this method finds problems, it returns an error messages object
* that encapsulates those problems, and the controller servlet will return
* control to the corresponding input form. Otherwise, the
* <code>validate</code> method returns <code>null</code>, indicating that
* everything is acceptable and the corresponding <code>Action.execute</code>
* method should be called.
*
* This class must be subclassed in order to be instantiated. Subclasses
* should provide property getter and setter methods for all of the bean
* properties they wish to expose, plus override any of the public or
* protected methods for which they wish to provide modified functionality.
* 
*
* Because ActionForms are JavaBeans, subclasses should also implement
* <code>Serializable</code>, as required by the JavaBean specification. Some
* containers require that an object meet all JavaBean requirements in order
* to use the introspection API upon which ActionForms rely.
*
* @version $Rev: 471754 $ $Date: 2005-11-12 08:14:24 -0500 (Sat, 12 Nov 2005)
* $
*/
public abstract class ActionForm implements Serializable {
 // ----------------------------------------------------- Instance Variables /**
 * The servlet instance to which we are attached.
 */
 protected transient ActionServlet servlet = null; /**
 * The MultipartRequestHandler for this form, can be
 * <code>null</code>.
 */
 protected transient MultipartRequestHandler multipartRequestHandler; // ------------------------------------------------------------- Properties /**
 * Return the servlet instance to which we are attached.
 *
 * @return The servlet instance to which we are attached.
 */
 protected ActionServlet getServlet() {
 return (this.servlet);
 } /**
 * Return the controller servlet instance to which we are attached. as
 * an <code>ActionServletWrapper</code>.
 *
 * @return An instance of {@link ActionServletWrapper}
 * @see ActionServletWrapper
 * @since Struts 1.0.1
 */
 public ActionServletWrapper getServletWrapper() {
 return new ActionServletWrapper(getServlet());
 } /**
 * Return the <code>MultipartRequestHandler</code> for this form The
 * reasoning behind this is to give form bean developers control over the
 * lifecycle of their multipart requests through the use of the
 * <code>finish</code> and/or <code>rollback</code> methods of
 * <code>MultipartRequestHandler</code>. This method will return
 * <code>null</code> if this form's enctype is not "multipart/form-data".
 * 
 *
 * @return The {@link org.apache.struts.upload.MultipartRequestHandler}
 * for this form.
 * @see org.apache.struts.upload.MultipartRequestHandler
 */
 public MultipartRequestHandler getMultipartRequestHandler() {
 return multipartRequestHandler;
 } /**
 * Set the servlet instance to which we are attached (if
 * <code>servlet</code> is non-null).
 *
 * @param servlet The new controller servlet, if any
 */
 public void setServlet(ActionServlet servlet) {
 this.servlet = servlet; // :FIXME: Should this be releasing resources?
 } /**
 * Set the Handler provided for use in dealing with file uploads.
 *
 * @param multipartRequestHandler The Handler to use for fileuploads.
 */
 public void setMultipartRequestHandler(
 MultipartRequestHandler multipartRequestHandler) {
 this.multipartRequestHandler = multipartRequestHandler;
 }
1、检查Action的映射，确定Action中已经配置了对ActionForm中的映射
2、根据name属性，找到FormBean的配置信息
3、检查Action的FormBean使用范围，确定在此范围下(Request,Session)是否已经有此FormBean的实例存在
4、加入当前范围下已经存在了此FormBean的实例，而是对于当前请求来说，是同一种类型的话，那么就重用
5、否则，就重新构造一个FormBean的实例(调用构造方法)并保存在一定作用范围下
6、FormBean的reset()方法被调用
7、调用对应的setter方法，对状态属性赋值
8、如果Validate的属性为true，那么就调用FormBean的Validate()方法
9、如果Validate()方法没有返回任何错误，控制器将ActionForm作为参数传给Action实例的execute()方法并执