最近读starting struts2 online，里面有一节Move CRUD Operations into the same Action，提供了Move CRUD Operations into the same Action大概的sample，于是进行了补充，记录下来，以备使用。
一、思路
在这本书里，lan roughley提到在结合preparable和ModenDriven拦截器实现Move CRUD Operations into the same Action，采用通配符的方式为所有的crud只写一个action配置，当然，这也要求相关文件的命名和目录组织的时候要遵循一定的要求，示例如下：
<action name="*/*" method="{2}"class="com.infoq.actions.{1}Action">
<result type="redirect">/{1}/view.action</result>
<result name="view">/{1}/view.jsp</result>
<result name="input">/{1}/edit.jsp</result>
<result name="home">/{1}/home.jsp</result>
</action>
采用这种方式后，所有的action的url都将是 “/{model}/{method}.action”的形式，从层次上看也比较的合理，更重要的是可以大幅度减少action配置的copy and paste
二、实现方式
具体工作的原理我就不多重复了，主要使用preparable和ModenDriven的拦截器，可以参考starting struts2 online，上面解释得非常清楚，只是我在具体实现的时候，方向采用"*/*" 的形式似乎不行，不得以改成了"*_*"了，哈哈，要是能改成"^_^"就更好了
注：在struts.xml中增加<constant name="struts.enable.SlashesInActionNames" value="true" />，可以使用"*/*"的方式
下面贴出具体的实现例子，同样了为了简化，在service层面上采取ArrayList模拟的数据库，下面贴代码：
Action 配置文件
因为要用preparable和modendriven，所以需要paramsPrepareParamsStack拦截器栈,下面会专门解释paramsPrepareParamsStack
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<package name="person" namespace="/person"
extends="struts-default">
<default-interceptor-ref name="paramsPrepareParamsStack" />
<!-- D?3¨¦person/add.action¦Ì¨¨url?¨¢11 -->
<action name="*_*" method="{2}"
class="com.work.action.person.{1}Action">
<result name="input">/pages/{1}/edit.jsp</result>
<result type="redirect">ListPersons.action</result>
</action>
<action name="ListPersons" class="com.work.action.person.ListPersons">
<result>/pages/Person/view.jsp</result>
</action>
<!-- Add actions here -->
</package>
</struts> PersonAction.java
package com.work.action.person;
import com.opensymphony.xwork2.ModelDriven;
import com.opensymphony.xwork2.Preparable;
import com.work.action.BaseSupport;
import com.work.model.Person;
import com.work.service.PersonService;
import com.work.service.PersonServiceImpl;
public class PersonAction extends BaseSupport implements ModelDriven<Person>,
Preparable 
{
private static final long serialVersionUID = 8115088127593809818L;
// 定义了作为model的person，因为使用了modeldriven，所以jsp中form的值会直接setter到person中
private Person person;
// id 用来保存用户的id，通过paramsPrepareParamsStack中的第一个param拦截器注入到action
private String id;
private PersonService service = new PersonServiceImpl();
public void prepare() throws Exception {
System.out.println(id);
if (id == null || id.length() == 0)
person = new Person();
else
person = service.find(id);
}
/** *//**
* delete
*/
public String delete() throws Exception {
log.info("delete the person");
service.deletePerson(id);
return SUCCESS;
}
/** *//**
* edit
*/
public String edit() {
return "input";
}
/** *//**
* add and update
*
* @return
* @throws Exception
*/
public String update() throws Exception {
if (id == null || id.length() == 0) {
log.info("add the person");
service.addPerson(person);
} else {
log.info("update the person");
service.updatePerson(person);
}
return SUCCESS;
}
/** *//**
* ??
*
* @return
*/
public String view() {
return SUCCESS;
}
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
public PersonService getService() {
return service;
}
public void setService(PersonService service) {
this.service = service;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public Person getModel() {
return person;
}
}
PersonListAction.java ：
package com.work.action.person;
import java.util.List;
import com.work.action.BaseSupport;
import com.work.model.Person;
import com.work.service.PersonService;
public class PersonListAction extends BaseSupport {
private static final long serialVersionUID = 1810482163716677456L;
private List<Person> people;
private PersonService service=new PersonServiceImpl(); ;
public String execute() throws Exception {
log.info("list persons");
people = service.getAllPersons();
return SUCCESS;
}
public List<Person> getPeople() {
return people;
}
public void setPeople(List<Person> people) {
this.people = people;
}
public PersonService getService() {
return service;
}
public void setService(PersonService service) {
this.service = service;
}
}
paramsPrepareParamsStack
这里需要说一下关键的paramsPrepareParamsStack拦截器，其中params拦截器出现了两次，第一次位于servletConfig和prepare之前，更在modelDriven之前，因此会将http://localhost:8080/diseaseMS/person/Person_edit.action?id=202中的参数id注入到action中，而不是model中，之后prepare将根据这个id，从服务层提取model。
下面是paramsPrepareParamsStack的英文注释：
An example of the params-prepare-params trick. This stack is exactly the same as the defaultStack, except that it includes one extra interceptor before the prepare interceptor:the params interceptor.
This is useful for when you wish to apply parameters directly to an object that you wish to load externally (such as a DAO or database or service layer), but can't load that object until at least the ID parameter has been loaded. By loadingthe parameters twice, you can retrieve the object in the prepare() method, allowing the second params interceptor toapply the values on the object.
<interceptor-stack name="paramsPrepareParamsStack">
<interceptor-ref name="exception"/>
<interceptor-ref name="alias"/>
<interceptor-ref name="params"/>
<interceptor-ref name="servletConfig"/>
<interceptor-ref name="prepare"/>
<interceptor-ref name="i18n"/>
<interceptor-ref name="chain"/>
<interceptor-ref name="modelDriven"/>
<interceptor-ref name="fileUpload"/>
<interceptor-ref name="checkbox"/>
<interceptor-ref name="staticParams"/>
<interceptor-ref name="params"/>
<interceptor-ref name="conversionError"/>
<interceptor-ref name="validation">
<param name="excludeMethods">input,back,cancel</param>
</interceptor-ref>
<interceptor-ref name="workflow">
<param name="excludeMethods">input,back,cancel</param>
</interceptor-ref>
</interceptor-stack>
package com.work.service;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import com.work.model.Person;
public class PersonServiceImpl implements PersonService {
/** *//**
* 示例程序，没有添加同步机制，多线程会有问题
*/
private List<Person> personList;
public PersonServiceImpl() {
personList = new ArrayList<Person>();
Person p1 = new Person("202", "name1", "beijing");
Person p2 = new Person("203", "name2", "beijing");
Person p3 = new Person("204", "name3", "tianjing");
personList.add(p1);
personList.add(p2);
personList.add(p3);
}
public void addPerson(Person person) {
if (person == null) {
throw new RuntimeException("add kong");
}
person.setId(getID(200));
personList.add(person);
}
public void deletePerson(String personID) {
int target = findLocation(personID);
if (target != -1)
personList.remove(target);
}
public List<Person> getAllPersons() {
return personList;
}
public void updatePerson(Person person) {
if (person == null) {
throw new RuntimeException("update kong");
}
int target = findLocation(person.getId());
personList.remove(target);
personList.add(person);
}
private int findLocation(String personID) {
int target = -1;
for (int i = 0; i < personList.size(); i++) {
if (personID.equals(personList.get(i).getId())) {
target = i;
break;
}
}
return target;
}
public Person find(String personID) {
Person person = null;
int target = findLocation(personID);
if (target != -1) {
person = personList.get(target);
}
return person;
}
private String getID(int round) {
Random rand = new Random();
int needed = rand.nextInt(round) + 1; // 1-linesum+1
return needed+"";
}
}
下面就是jsp文件了，就只贴部分了：
edit.jsp:
<s:form action="Person_update.action" >
<s:textfield label="your ID" name="id" readonly="true"/>
<s:textfield label="Please enter your name" name="name" required="true" />
<s:textfield label="Please enter your homeaddr" name="homeAddr" required="true"/>
<s:submit />
</s:form>
view.jsp
<%@ page contentType="text/html; charset=UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<title>person view</title>
</head>
<body>
<s:actionerror />
<table>
<tr>
<td>id</td>
<td>name</td>
<td>address</td>
<td></td>
<td></td>
</tr>
<s:iterator value="people">
<tr>
<td><s:property value="id" /></td>
<td><s:property value="name" /></td>
<td><s:property value="homeAddr" /></td>
<td><s:url id="update" action="Person_edit.action" >
<s:param name="id">
<s:property value="%{id}" />
</s:param>
</s:url> <s:a href="%{update}">修改</s:a>
</td>
<td><s:url id="delete" action="Person_delete.action">
<s:param name="id">
<s:property value="%{id}" />
</s:param>
</s:url> <s:a href="%{delete}">删除</s:a>
</td>
</tr>
</s:iterator>
</table>
<ul>
<li><a href="<s:url action="Person_input"/>">Create a new person</a></li>
</ul>
</body>
</html>
三、总结
优点：适用与crud比较的应用程序，大幅减少action的配置信息
其他：
1、也可以不实现modeldriven接口，只不过要在jsp中加上model.properity
2、这种方式在某种程度上透露了action中的方法名称给客户端，是否会带来安全性的问题