最近讀starting struts2 online，里面有一節(jié)Move CRUD Operations into the same Action,，提供了Move CRUD Operations into the same Action大概的sample,，于是進(jìn)行了補(bǔ)充，記錄下來,，以備使用,。
一、思路
在這本書里,，lan roughley提到在結(jié)合preparable和ModenDriven攔截器實(shí)現(xiàn)Move CRUD Operations into the same Action,，采用通配符的方式為所有的crud只寫一個action配置，當(dāng)然,，這也要求相關(guān)文件的命名和目錄組織的時候要遵循一定的要求,，示例如下：
<action name="**" 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"*
public String delete() throws Exception {
log.info("delete the person");
service.deletePerson(id);
return SUCCESS;
}
public String edit() {
return "input";
}
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;
}
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
這里需要說一下關(guān)鍵的paramsPrepareParamsStack攔截器,，其中params攔截器出現(xiàn)了兩次,，第一次位于servletConfig和prepare之前，更在modelDriven之前,，因此會將http://localhost:8080/diseaseMS/person/Person_edit.action?id=202中的參數(shù)id注入到action中,，而不是model中，之后prepare將根據(jù)這個id,，從服務(wù)層提取model,。
下面是paramsPrepareParamsStack的英文注釋：
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>
PersonServiceImpl.java
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 {
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，就只貼部分了：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}">刪除</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,、總結(jié)
優(yōu)點(diǎn)：適用與crud比較的應(yīng)用程序,，大幅減少action的配置信息
其他：
1,、也可以不實(shí)現(xiàn)modeldriven接口，只不過要在jsp中加上model.properity
2,、這種方式在某種程度上透露了action中的方法名稱給客戶端,，是否會帶來安全性的問題
使用場景:
如果action針對每次請求都要執(zhí)行一些相同的業(yè)務(wù)邏輯， 那么可以實(shí)現(xiàn)Preparable接口,， 將預(yù)處理業(yè)務(wù)邏輯寫在prepare()方法里
Preparable 接口定義:
public interface Preparable {
void prepare() throws Exception;
}
prepare何時被執(zhí)行:
prepare方法由PrepareInterceptor攔截器調(diào)用執(zhí)行
com.opensymphony.xwork2.interceptor.PrepareInterceptor
public String doIntercept(ActionInvocation invocation) throws Exception {
Object action = invocation.getAction();
if (action instanceof Preparable) {
try {
String[] prefixes;
if (firstCallPrepareDo) {
prefixes = new String[] {ALT_PREPARE_PREFIX, PREPARE_PREFIX};
} else {
prefixes = new String[] {PREPARE_PREFIX, ALT_PREPARE_PREFIX};
}
PrefixMethodInvocationUtil.invokePrefixMethod(invocation, prefixes);
}
catch (InvocationTargetException e) {
// just in case there's an exception while doing reflection,
// we still want prepare() to be able to get called.
LOG.warn("an exception occured while trying to execute prefixed method", e);
}
catch (IllegalAccessException e) {
// just in case there's an exception while doing reflection,
// we still want prepare() to be able to get called.
LOG.warn("an exception occured while trying to execute prefixed method", e);
} catch (Exception e) {
// just in case there's an exception while doing reflection,
// we still want prepare() to be able to get called.
LOG.warn("an exception occured while trying to execute prefixed method", e);
}
// 必須執(zhí)行或初始化的一些業(yè)務(wù)操作 action prepare()方法
if (alwaysInvokePrepare) {
((Preparable) action).prepare();
}
}
return invocation.invoke();
}
使用方法:
使用basicStack攔截器棧
<action name="list" class="org.apache.struts2.showcase.action.SkillAction" method="list">
<result>/empmanager/listSkills.jsp</result>
<interceptor-ref name="basicStack" /> <!-- 使用basicStack攔截器棧, 該攔截器棧在 struts-default.xml 已配置, 包括了prepare -->
</action>
(注: struts-default.xml 里定義的 basicStack攔截器棧
<!-- Basic stack -->
<interceptor-stack name="basicStack">
<interceptor-ref name="exception"/>
<interceptor-ref name="servletConfig"/>
<interceptor-ref name="prepare"/>
<interceptor-ref name="checkbox"/>
<interceptor-ref name="multiselect"/>
<interceptor-ref name="actionMappingParams"/>
<interceptor-ref name="params">
<param name="excludeParams">dojo\..*,^struts\..*</param>
</interceptor-ref>
<interceptor-ref name="conversionError"/>
</interceptor-stack>
)
或者直接指定prepare攔截器
<action name="list" class="org.apache.struts2.showcase.action.SkillAction" method="list">
<result>/empmanager/listSkills.jsp</result>
<interceptor-ref name="prepare" /> <!-- 直接指定prepare攔截器 -->
</action>
