Struts的动态表单的应用

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Struts的动态表单的应用

原文连接:http://www.developer.com/java/web/article.php/2214681

By James M. Turner

 

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("success");

    }

}

 

 

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。

 

下图添加customer空表单图片

 

如果什么也没有填就提交了,将会出现下图的反馈信息:

 

如果你所有输入的信息都合法,那么在控制台你可以看到如下类似的信息:

 

lastName = Bush

firstName = George

street = 1600 Pennsylvania Avenue NW

city = Washington

state = DC

postalCode = 20500

phone = 2024561414

 

 

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 [email protected].

 

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