Struts2MVC底層的簡單實現

一直想寫Struts2的底層實現，醞釀了兩個星期，今天把它實現。

首先，我們在運用的時候都會使用action，實現跳轉，下面我們寫一個UserAction:

public class UserAction {    public String toAddUser(){        return "success";    }                                                                                                                                                                                                                                                           public String addUser(){        return "adduser";    }}

我們在使用Struts2的時候，一個很重要的設定檔是：struts.xml，因此我們需要讀取它，知道他裡面的內容，java解析xml我寫過了一篇文章，可以去看看。

下面我們寫一個設定檔：

<?xml version="1.0" encoding="UTF-8"?><struts>   <package name="user" namespace="/user" >       <action name="userAction" class="actions.UserAction" >          <result name="success">/success.jsp</result>          <result name="adduser">/addUser.jsp</result>       </action>   </package></struts>

之後我們就需要去讀取這個設定檔，但是之前我們需要我們需要建立幾個實體類去儲存這些元素，由外到內排列：

1.package的實體類

import java.util.List;public class PackageEntity {                                                                                                                                                                                                              private String name;    private String namespace;    private List<ActionEntity> actions;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getNamespace() {        return namespace;    }    public void setNamespace(String namespace) {        this.namespace = namespace;    }    public List<ActionEntity> getActions() {        return actions;    }    public void setActions(List<ActionEntity> actions) {        this.actions = actions;    }}

private List<ActionEntity> actions;是吧action實體類的內容放到package中。

2.action的實體類

import java.util.List;public class ActionEntity {    private String name;    private String classname;    private List<ResultEntity> results;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getClassname() {        return classname;    }    public void setClassname(String classname) {        this.classname = classname;    }    public List<ResultEntity> getResults() {        return results;    }    public void setResults(List<ResultEntity> results) {        this.results = results;    }}

private List<ResultEntity> results;是把result的實體類放到action中。

3.result的實體類

public class ResultEntity {    private String name;    private String page;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getPage() {        return page;    }    public void setPage(String page) {        this.page = page;    }}

page是指後面的jsp。

經過兩個list就把設定檔中所有的元素集中到package中，便於下面的跳轉。

下面寫一個配置的工具類：

public class ConfigUtils {//new一個package的對象，便於調用元素    public static  PackageEntity pe=new PackageEntity();                                                                                                                                                                                                                                                                                           public static void config(){         SAXReader reader=new SAXReader();         try {             //讀取struts.xml            Document doc=reader.read(Thread.currentThread().getContextClassLoader().getResourceAsStream("struts.xml"));            //讀取根項目            Element root=doc.getRootElement();          //得到根項目下的節點元素            Element packageElement=root.element("package");            List<ActionEntity> actions=new ArrayList<ActionEntity>();            pe.setName(packageElement.attributeValue("name"));            pe.setNamespace(packageElement.attributeValue("namespace"));          //得到根項目下的節點元素            List<Element> listActions=packageElement.elements("action");            for(Element actionElement:listActions){                ActionEntity ae=new ActionEntity();                //得到子節點                ae.setName(actionElement.attributeValue("name"));                ae.setClassname(actionElement.attributeValue("class"));                //得到根項目下的節點元素                List<Element> resultElements=actionElement.elements("result");                List<ResultEntity>  results=new ArrayList<ResultEntity>();                for(Element resultEle:resultElements){                    ResultEntity re=new ResultEntity();                    //得到子節點                    re.setName(resultEle.attributeValue("name"));                    re.setPage(resultEle.getText());                    results.add(re);                }                ae.setResults(results);                actions.add(ae);            }            pe.setActions(actions);                                                                                                                                                            } catch (DocumentException e) {            e.printStackTrace();        }    }}

寫一個index.jsp，為了寫跳轉連結進行驗證：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>     <title>首頁</title>  </head>                                                                                                                                   <body>      <a href="<%=path%>/user/userAction!toAddUser.action">跳轉</a>      <br/>      <a href="<%=path%>/user/userAction!addUser.action">添加使用者</a>  </body></html>

跳轉是跳到到success.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>   <title>My JSP 'success.jsp' starting page</title>  </head>                                                                                                                               <body>    This is my JSP page. <br>    成功了  </body></html>

添加使用者是跳到adduser.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>     <title>My JSP 'addUser.jsp' starting page</title>  </head>                                                                                                                        <body>    This is my JSP page. <br>    添加使用者了  </body></html>

寫好了jsp之後我們就要過濾這些串連，進行跳轉，寫一個struts2的過濾器：

public class StrutsFilter implements Filter {    @Override    public void destroy() {                                                                                                                      }    @Override    public void doFilter(ServletRequest req, ServletResponse res,            FilterChain chain) throws IOException, ServletException {        HttpServletRequest request=(HttpServletRequest)req;        String path=request.getServletPath();        System.out.println(path);        String[] pathArr=path.split("/");        String namespace=pathArr[1];        String actionString=pathArr[2];        String actionname=actionString.split("!")[0];        String methodname=actionString.split("!")[1].split("\\.")[0];        System.out.println(actionname+":"+methodname);        PackageEntity pe=ConfigUtils.pe;        List<ActionEntity> actions=pe.getActions();        ActionEntity doAction=null;        for(ActionEntity ae:actions){            if(ae.getName().equals(actionname)){                doAction=ae;                break;            }        }                                                                                                                          try {            Class actioncls=Class.forName(doAction.getClassname());            Object actionObj=actioncls.newInstance();            Class cls=actionObj.getClass();            Method actionMethod=cls.getDeclaredMethod(methodname);    String resultValue=(String)actionMethod.invoke(actionObj,null);            List<ResultEntity> results=doAction.getResults();            ResultEntity re=null;            for(ResultEntity result:results){                if(resultValue.equals(result.getName())){                    re=result;                    break;                }            }     request.getRequestDispatcher(re.getPage()).forward(request, res);        } catch (Exception e) {            e.printStackTrace();        }    }    @Override    public void init(FilterConfig filterConfig) throws ServletException {         ConfigUtils.config();        }}

下面建立一個web的過濾器測試一下：

import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class TestFilter implements Filter {    @Override    public void destroy() {    }    @Override    public void doFilter(ServletRequest req, ServletResponse res,            FilterChain chain) throws IOException, ServletException {         HttpServletRequest request=(HttpServletRequest)req;        HttpServletResponse response=(HttpServletResponse)res;         request.getRequestDispatcher("/success.jsp").forward(request,response);     }    @Overridepublic void init(FilterConfig filterConfig) throws ServletException {    }}

建立一個web的servlet測試一下：

import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class TestServlet extends HttpServlet {public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{request.getRequestDispatcher("/success.jsp").forward(request, response);    }}

別忘了把解析xml的包導進去。

希望對你們理解架構有協助！！！

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