关于struts2中prepare接口实现数据准备

之前做过不少的项目，所有的action只实现了一个execute()方法，也用到过Preparable接口，并没注意到它的具体用法。随着项目的需求的增加，按照以前的方法，每一个功能都需要一个action，这样势必会造成action类的大规模膨胀。所以决定采取action!method的形式，这样在一个action中可以包含很多方法，减少了action类的数量，也便于维护。

把crud方法放在一个action类中，就必定会涉及到一些数据准备的事情，所以用Preparable接口就再合适不过了，实现这个接口的 prepare()方法，这个方法会在action类的所有方法执行前执行，另外我们也可以按照它的规则来写一些其它形式的prepare方法，例如 aciton中有一个方法叫input(),那么我们可以实现一个prepareInput方法，这样在input()执行前，会执行 prepareInput()方法。

好了，言归正传，我们有这样的一个action:

Java代码

package ht.gisoa.action;
import ht.gisoa.model.Sysconfig;
import ht.gisoa.service.SysconfigManager;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import com.opensymphony.webwork.ServletActionContext;
import com.opensymphony.webwork.interceptor.ServletRequestAware;
import com.opensymphony.webwork.interceptor.SessionAware;
import com.opensymphony.xwork.ActionSupport;
import com.opensymphony.xwork.ModelDriven;
import com.opensymphony.xwork.Preparable;
import com.thoughtworks.xstream.XStream;
public class SystemConfigAction extends ActionSupport implements Preparable,SessionAware,ServletRequestAware,ModelDriven{
/**
*
*/
private Map session ;
private HttpServletRequest request;
private NamedParameterJdbcTemplate namedParameterJdbcTemplate = null ;
private Double hignSpeed = 0.0 ;
private Double midSpeed = 0.0 ;
private Double lowSpeed = 0.0 ;
private static final long serialVersionUID = 1L;
private SysconfigManager sysconfigManager = null ;
private Long id ;
private Sysconfig entity;
public void setId(Long id) {
this .id = id;
}
public String editSpeed() throws Exception{
Map<String,Sysconfig> configs = sysconfigManager.getSpeedConfig() ;
ServletActionContext.getRequest().setAttribute("configs" , configs);
return this .SUCCESS;
}
public String input() throws Exception{
return "input" ;
}
public String list(){
List<Sysconfig> speedCollection = sysconfigManager.getSpeedList();
ServletActionContext.getRequest().setAttribute("speedCollection" , speedCollection);
return "list" ;
}
public String save() throws Exception{
sysconfigManager.mergy(entity);
return "reload" ;
}
public String delete() throws Exception{
sysconfigManager.delete(id);
return "reload" ;
}
public SysconfigManager getSysconfigManager() {
return sysconfigManager;
}
public void setSysconfigManager(SysconfigManager sysconfigManager) {
this .sysconfigManager = sysconfigManager;
}
public Double getHignSpeed() {
return hignSpeed;
}
public void setHignSpeed(Double hignSpeed) {
this .hignSpeed = hignSpeed;
}
public Double getMidSpeed() {
return midSpeed;
}
public void setMidSpeed(Double midSpeed) {
this .midSpeed = midSpeed;
}
public Double getLowSpeed() {
return lowSpeed;
}
public void setLowSpeed(Double lowSpeed) {
this .lowSpeed = lowSpeed;
}
public void setSession(Map session) {
this .session = session;
}
public void setServletRequest(HttpServletRequest request) {
this .request = request;
}
public void prepare() throws Exception {
}
public void prepareModel() throws Exception {
if (id== null ){
System.out.println("id=null" );
entity = new Sysconfig();
entity.setKeyType(1L);
}else {
System.out.println("id==" +id);
entity = sysconfigManager.get(id);
}
}
public void prepareInput() throws Exception{
prepareModel();
}
public void prepareSave() throws Exception {
prepareModel();
}
public Object getModel() {
return entity;
}
}

这里要注意，要在spring中配置该action的作用域为prototype,否则，不同的方法之间会出现数据混乱的情况：

Xml代码

< bean id = "systemconfig"
class = "ht.gisoa.action.SystemConfigAction" scope = "prototype" >
< property name = "sysconfigManager" >
< ref bean = "SysconfigManager" />
</ property >
</ bean >

sysconfig_input.jsp代码如下：

Jsp代码

<%@ page language= "java" pageEncoding= "UTF-8" isELIgnored= "false" %>
<%@ taglib uri="http://java.sun.com/jstl/core_rt" prefix= "c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd" >
<html>
<head>
<meta http-equiv="Content-Type" content= "text/html; charset=UTF-8" >
</head>
<body>
<div id="msg" >
${msg}
</div>
<c:choose><c:when test="${ param.id == null}" >创建</c:when><c:otherwise>修改</c:otherwise></c:choose>设置
<div id="main" >
<form action="systemconfig!save.action" >
<input type="text" name= "model.keyName" value= "${model.keyName}" /><br>
<input type="text" name= "model.keyValue" value= "${model.keyValue}" /><br>
<input type="hidden" name= "model.id" value= "${model.id}" /><br>
<input type="hidden" name= "model.keyType" value= "1" /><br>
<input type="submit" value= "修改" />
</form>
</div>
<c:remove var="msg" scope= "session" />
</body>
</html>

我们编辑完信息，提交后，会执行action中的save方法，按道理，表单提交后，会将action中的model填充好数据，但是save方法之前又会执行prepareSave方法，从数据库里获取一次数据，这样不就把之前填充好的数据冲掉了吗？仔细想想也确实是这样的.

     那么该如何解决这种矛盾呢，立即使出google大法，查了一下关于interceptor的资料，有这样的一个 interceptor：paramsPrepareParamsStack，paramsPrepareParamsStack主要解决了 ModelDriven和Preparable的配合问题，从字面上理解来说，这个stack的拦截器调用的顺序为：首先params，然后 prepare，接下来modelDriven，最后再params。Struts 2.0的设计上要求modelDriven在params之前调用，而业务中prepare要负责准备model，准备model又需要参数，这就需要在 prepare之前运行params拦截器设置相关参数，这个也就是创建paramsPrepareParamsStack的原因。流程如下：
   1. params拦截器首先给action中的相关参数赋值，如id
   2. prepare拦截器执行prepare方法，prepare方法中会根据参数，如id，去调用业务逻辑，设置model对象
   3. modelDriven拦截器将model对象压入value stack，这里的model对象就是在prepare中创建的
   4. params拦截器再将参数赋值给model对象
   5. action的业务逻辑执行

我的xwork.xml中相关配置如下：

Xml代码

< action name = "systemconfig" class = "systemconfig" >
< result name = "list" type = "dispatcher" >
< param name = "location" > syscfg_speed_list.jsp </ param >
</ result >
< result name = "reload" type = "redirect" >
< param name = "location" > systemconfig!list.action </ param >
</ result >
< result name = "input" type = "dispatcher" >
< param name = "location" > syscfg_speed_input.jsp </ param >
</ result >
< interceptor-ref name = "paramsPrepareParamsStack" />
< interceptor-ref name = "modelParamsStack" > </ interceptor-ref >
</ action >

通过paramsPrepareParamsStack可以让流程更明确，代码更简洁，也更利于大家的交流。

好了，言归正传，我们有这样的一个action:

Java代码

package ht.gisoa.action;
import ht.gisoa.model.Sysconfig;
import ht.gisoa.service.SysconfigManager;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import com.opensymphony.webwork.ServletActionContext;
import com.opensymphony.webwork.interceptor.ServletRequestAware;
import com.opensymphony.webwork.interceptor.SessionAware;
import com.opensymphony.xwork.ActionSupport;
import com.opensymphony.xwork.ModelDriven;
import com.opensymphony.xwork.Preparable;
import com.thoughtworks.xstream.XStream;
public class SystemConfigAction extends ActionSupport implements Preparable,SessionAware,ServletRequestAware,ModelDriven{
/**
*
*/
private Map session ;
private HttpServletRequest request;
private NamedParameterJdbcTemplate namedParameterJdbcTemplate = null ;
private Double hignSpeed = 0.0 ;
private Double midSpeed = 0.0 ;
private Double lowSpeed = 0.0 ;
private static final long serialVersionUID = 1L;
private SysconfigManager sysconfigManager = null ;
private Long id ;
private Sysconfig entity;
public void setId(Long id) {
this .id = id;
}
public String editSpeed() throws Exception{
Map<String,Sysconfig> configs = sysconfigManager.getSpeedConfig() ;
ServletActionContext.getRequest().setAttribute("configs" , configs);
return this .SUCCESS;
}
public String input() throws Exception{
return "input" ;
}
public String list(){
List<Sysconfig> speedCollection = sysconfigManager.getSpeedList();
ServletActionContext.getRequest().setAttribute("speedCollection" , speedCollection);
return "list" ;
}
public String save() throws Exception{
sysconfigManager.mergy(entity);
return "reload" ;
}
public String delete() throws Exception{
sysconfigManager.delete(id);
return "reload" ;
}
public SysconfigManager getSysconfigManager() {
return sysconfigManager;
}
public void setSysconfigManager(SysconfigManager sysconfigManager) {
this .sysconfigManager = sysconfigManager;
}
public Double getHignSpeed() {
return hignSpeed;
}
public void setHignSpeed(Double hignSpeed) {
this .hignSpeed = hignSpeed;
}
public Double getMidSpeed() {
return midSpeed;
}
public void setMidSpeed(Double midSpeed) {
this .midSpeed = midSpeed;
}
public Double getLowSpeed() {
return lowSpeed;
}
public void setLowSpeed(Double lowSpeed) {
this .lowSpeed = lowSpeed;
}
public void setSession(Map session) {
this .session = session;
}
public void setServletRequest(HttpServletRequest request) {
this .request = request;
}
public void prepare() throws Exception {
}
public void prepareModel() throws Exception {
if (id== null ){
System.out.println("id=null" );
entity = new Sysconfig();
entity.setKeyType(1L);
}else {
System.out.println("id==" +id);
entity = sysconfigManager.get(id);
}
}
public void prepareInput() throws Exception{
prepareModel();
}
public void prepareSave() throws Exception {
prepareModel();
}
public Object getModel() {
return entity;
}
}

这里要注意，要在spring中配置该action的作用域为prototype,否则，不同的方法之间会出现数据混乱的情况：

Xml代码

< bean id = "systemconfig"
class = "ht.gisoa.action.SystemConfigAction" scope = "prototype" >
< property name = "sysconfigManager" >
< ref bean = "SysconfigManager" />
</ property >
</ bean >

sysconfig_input.jsp代码如下：

Jsp代码

<%@ page language= "java" pageEncoding= "UTF-8" isELIgnored= "false" %>
<%@ taglib uri="http://java.sun.com/jstl/core_rt" prefix= "c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd" >
<html>
<head>
<meta http-equiv="Content-Type" content= "text/html; charset=UTF-8" >
</head>
<body>
<div id="msg" >
${msg}
</div>
<c:choose><c:when test="${ param.id == null}" >创建</c:when><c:otherwise>修改</c:otherwise></c:choose>设置
<div id="main" >
<form action="systemconfig!save.action" >
<input type="text" name= "model.keyName" value= "${model.keyName}" /><br>
<input type="text" name= "model.keyValue" value= "${model.keyValue}" /><br>
<input type="hidden" name= "model.id" value= "${model.id}" /><br>
<input type="hidden" name= "model.keyType" value= "1" /><br>
<input type="submit" value= "修改" />
</form>
</div>
<c:remove var="msg" scope= "session" />
</body>
</html>

我的xwork.xml中相关配置如下：

Xml代码

< action name = "systemconfig" class = "systemconfig" >
< result name = "list" type = "dispatcher" >
< param name = "location" > syscfg_speed_list.jsp </ param >
</ result >
< result name = "reload" type = "redirect" >
< param name = "location" > systemconfig!list.action </ param >
</ result >
< result name = "input" type = "dispatcher" >
< param name = "location" > syscfg_speed_input.jsp </ param >
</ result >
< interceptor-ref name = "paramsPrepareParamsStack" />
< interceptor-ref name = "modelParamsStack" > </ interceptor-ref >
</ action >

通过paramsPrepareParamsStack可以让流程更明确，代码更简洁，也更利于大家的交流。

关于struts2中prepare接口实现数据准备

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