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Struts的动态表单的应用
发表于：2007-07-04来源：作者：点击数：
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这篇文章以实例代码来阐述Dynaforms在struts1.1种的引用??译者注 如果你使用过struts先前的版本，你就会注意到你需要花费大量的时候来写ActionForm类文件，而这些类文件对于struts都是非常关键的（它充当“View”的一部分），通常它的结构就是beanproperties
这篇文章以实例代码来阐述Dynaforms在struts1.1种的引用??译者注 如果你使用过struts先前的版本，你就会注意到你需要花费大量的时候来写ActionForm类文件，而这些类文件对于struts都是非常关键的（它充当“View”的一部分），通常它的结构就是bean properties在加上一个validate方法（有时还有reset方法）。
随着struts1.1版本的推出，开发员有了另外一种方法来完成前面的任务：使用DynaBeans。DynaBeans动态生成Java Beans。这就意味着我们可以通过配置（通常利用xml）
来生成formbean而不是在formbean中硬编码。
为了了解DynaBeans（struts中为Dynaforms）是如何工做的，让我们看一个简单的表单，字段有：name，address，telephone等，下面的代码为通常的写法（没有使用Dynaforms）。
article1.CustomerForm
package article1;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionErrors;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionError;
import javax.servlet.http.HttpServletRequest;
public class CustomerForm extends ActionForm {
protected boolean nullOrBlank (String str) {
return ((str == null) || (str.length() == 0));
}
public ActionErrors validate(ActionMapping mapping,
HttpServletRequest request) {
ActionErrors errors = new ActionErrors();
if (nullOrBlank(lastName)) {
errors.add("lastName",
new ActionError("article1.lastName.missing"));
}
if (nullOrBlank(firstName)) {
errors.add("firstName",
new ActionError("article1.firstName.missing"));
}
if (nullOrBlank(street)) {
errors.add("street",
new ActionError("article1.street.missing"));
}
if (nullOrBlank(city)) {
errors.add("city",
new ActionError("article1.city.missing"));
}
if (nullOrBlank(state)) {
errors.add("state",
new ActionError("article1.state.missing"));
}
if (nullOrBlank(postalCode)) {
errors.add("postalCode",
new ActionError("article1.postalCode.missing"));
}
if (nullOrBlank(phone)) {
errors.add("phone",
new ActionError("article1.phone.missing"));
}
return errors;
}
private String lastName;
private String firstName;
private String street;
private String city;
private String state;
private String postalCode;
private String phone;
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public String getPostalCode() {
return postalCode;
}
public void setPostalCode(String postalCode) {
this.postalCode = postalCode;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
}
看到上边的写法（这么长一段代码[虽然大多的工具都可以自动生成set和get方法]感想如何？如果要为每一个表单配备一个formbean，那么将是一件多了令人痛苦的事情??译者注），你知道了它是一个标准的JavaBean，只是多了一个validate方法，validate方法确保client断的输入都是合法的。
相应的jsp页面同样也是很简单的，如下：
customer.jsp
<%@ taglib uri="/WEB-INF/c.tld" prefix="c" %>
<%@ taglib prefix="fmt" uri="/WEB-INF/fmt.tld" %>
<%@ taglib uri="/WEB-INF/struts-tiles.tld" prefix="tiles" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<head>
<title>Example of a standard Customer form</title>
</head>
<h1>Example of a standard Customer form</h1>
<html:form action="/addCustomer">
Last Name: <html:text property="lastName"/>
<html:errors property="lastName" /><br>
First Name: <html:text property="firstName"/>
<html:errors property="firstName" /><br>
Street Addr: <html:text property="street"/>
<html:errors property="street" /><br>
City: <html:text property="city"/>
<html:errors property="city" /><br>
State: <html:text property="state" maxlength="2" size="2" />
<html:errors property="state" /><br>
Postal Code: <html:text property="postalCode" maxlength="5"
size="5" />
<html:errors property="postalCode" /><br>
Telephone: <html:text property="phone" maxlength="11" size="11" />
<html:errors property="phone" /><br>
<html:submit/>
</html:form>
相应的action也没有复杂的业务代码，只是将从client端传过来的值打印到控制台。
article1.AddCustomerAction
package article1;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionForm;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import java.io.IOException;
public class AddCustomerAction extends Action {
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException{
CustomerForm custForm = (CustomerForm) form;
System.out.println("lastName = "
+ custForm.getLastName());
System.out.println("firstName = "
+ custForm.getFirstName());
System.out.println("street = " + custForm.getStreet());
System.out.println("city = " + custForm.getCity());
System.out.println("state = " + custForm.getState());
System.out.println("postalCode = "
+ custForm.getPostalCode());
System.out.println("phone = " + custForm.getPhone());
return mapping.findForward("suclearcase/" target="_blank" >ccess");
}
}
下面看看struts-config.xml的配置，struts利用该配置文件将上述文件联系到一起来协同完成任务。
<struts-config>
<form-beans>
<form-bean name="customerForm" type="jdj.article1.Customer" />
</form-beans>
<action-mappings>
<action path="/addCustomer" type="article1.AddCustomerAction"
name="customerForm" scope="request"
input="/addCustomer.jsp">
<forward name="success" path="/addCustomerSucceeded.jsp"
redirect="false" />
</action>
</action-mappings>
<message-resources parameter="ApplicationResources" />
<plug-in className="org.apache.struts.validator.ValidatorPlugIn">
<set-property value="/WEB-INF/validator-rules.xml"
property="pathnames" />
struts-config.xml</plug-in></struts-config>
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts-config PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 1.1//EN"
"http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd">
<struts-config>
<form-beans>
<form-bean name="customerForm" type="article1.CustomerForm" />
</form-beans>
<action-mappings>
<action path="/addCustomer" type="article1.AddCustomerAction"
name="customerForm" scope="request" input="/customer.jsp">
<forward name="success" path="/addCustomerSucceeded.jsp"
redirect="false" />
</action>
</action-mappings>
<message-resources parameter="ApplicationResources" />
<plug-in className="org.apache.struts.validator.ValidatorPlugIn">
<set-property value="/WEB-INF/validator-rules.xml"
property="pathnames" />
</plug-in>
</struts-config>
上边通过配置，customerForm来引用CustemerForm类， “/addCustomer”action使用customerForm并且触发article1.AddCustomerAction来处理请求。
到现在为止，上边代码熟悉struts得都应该很熟悉但是，如果应用struts1.1的新特性，你将会用更少的代码来完成上述同样的功能。使用Dynaforms,我们应该更改customerForm在struts-config.xml中信息来使用org.apache.struts.action.DynaActionForm （为了便于读者比较使用前后的差别，我们将使用新的类新的jsp页面来完成同样的功能）
使用DynaActionForm，你可以利用form-property xml标签，它允许你在struts-config.xml中定义formbean的属性元素。以我们的例子来说，struts-config.xml中将是如下这个样子：
<form-bean name="dynaCustomerForm"
type="org.apache.struts.action.DynaActionForm">
<form-property name="lastName" type="java.lang.String"/>
<form-property name="firstName" type="java.lang.String"/>
<form-property type="java.lang.String" name="street"/>
<form-property name="city" type="java.lang.String"/>
<form-property name="state" type="java.lang.String"/>
<form-property name="postalCode" type="java.lang.String"/>
</form-bean>
上边的改动对于jsp页面没有任何的影响。不过你要对于原来的action进行稍微的改动应为：你现在已经不在向execute()中传递formbean（没有get set方法），所以 你应该把form转型到DynaActionForm，然后利用方法get(filename)来取得client端数据新的action代码如下：
article1.AddDynaCustomerAction
package article1;
import org.apache.struts.action.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import java.io.IOException;
public class AddDynaCustomerAction extends Action {
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException{
DynaActionForm custForm = (DynaActionForm) form;
System.out.println("lastName = " + custForm.get("lastName"));
System.out.println("firstName = " + custForm.get("firstName"));
System.out.println("street = " + custForm.get("street"));
System.out.println("city = " + custForm.get("city"));
System.out.println("state = " + custForm.get("state"));
System.out.println("postalCode = "
+ custForm.get("postalCode"));
System.out.println("phone = " + custForm.get("phone"));
return mapping.findForward("success");
}
}
从上边的代码可以看出，似乎”屏蔽“了actionform，然而我们也“丢失”了一些其他的，譬如：严整输入合法性的问题。有两种方法可以恢复校验功能：一是创建一个DynaActionForm的子类，然后在子类中实现validate()方法。如下代码：
article1.DynaCustomerForm
package article1;
import org.apache.struts.action.*;
import javax.servlet.http.HttpServletRequest;
public class DynaCustomerForm extends DynaActionForm {
protected boolean nullOrBlank (String str) {
return ((str == null) || (str.length() == 0));
}
public ActionErrors validate(ActionMapping mapping,
HttpServletRequest request) {
ActionErrors errors = new ActionErrors();
if (nullOrBlank((String)this.get("lastName"))) {
errors.add("lastName",
new ActionError("article1.lastName.missing"));
}
if (nullOrBlank((String)this.get("firstName"))) {
errors.add("firstName",
new ActionError("article1.firstName.missing"));
}
if (nullOrBlank((String)this.get("street"))) {
errors.add("street",
new ActionError("article1.street.missing"));
}
if (nullOrBlank((String)this.get("city"))) {
errors.add("city", new ActionError("article1.city.missing"));
}
if (nullOrBlank((String)this.get("state"))) {
errors.add("state",
new ActionError("article1.state.missing"));
}
if (nullOrBlank((String)this.get("postalCode"))) {
errors.add("postalCode",
new ActionError("article1.postalCode.missing"));
}
if (nullOrBlank((String)this.get("phone"))) {
errors.add("phone", new ActionError("article1.phone.missing"));
}
return errors;
}
}
如果是这样，我们就要更改struts-config.xml来使用DynaActionForm的子类，这样的效果似乎是又回到了先前的样子（为每一个表单写DynaActionForm），呵呵。。。
所以推荐的做法是使用struts1.1种的Validator Framework,这方面的内容在以后的文章中在说明。
关于作者：
James Turner is the owner and manager of Black Bear Software, LLC, which specializes in custom Java-based e-Commerce and CRM solutions delivery. He is also the author of "MySQL and JSP Web Applications: Data-Driven Programming Using Tomcat and MySQL" (ISBN: 0672323095) and is the co-author of "Struts: Kick Start" (ISBN: 0672324725), which will be published in November. He can be reached at turner@blackbear.com.
