struts2的结构图：
代码实现：
组织结构：
主要代码：
package cn.itcast.config; import org.apache.log4j.Logger;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader; import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map; /**
* Created by zhen on 2017-08-04.
* 读取struts.xml配置信息
*/
public class ConfigurationManager {
private static final Logger logger = Logger.getLogger(ConfigurationManager.class); //读取Interceptor
public static List<String> getInterceptors(){
List<String> interceptors = null;
SAXReader saxReader = new SAXReader();
InputStream inputStream = ConfigurationManager.class.getResourceAsStream("/struts.xml");
Document document = null;
try {
document = saxReader.read(inputStream);
} catch (DocumentException e) {
logger.error(e.getMessage());
throw new RuntimeException("配置文件解析异常" ,e);
}
String xpath = "//interceptor";
List<Element> list = document.selectNodes(xpath);
if(list != null && list.size() > 0){
interceptors = new ArrayList<String>();
for(Element ele: list){
String className = ele.attributeValue("class");
interceptors.add(className);
}
}
return interceptors;
} //读取Constant
public static String getConstant(String name){
String value = null;
SAXReader saxReader = new SAXReader();
InputStream is = ConfigurationManager.class.getResourceAsStream("/struts.xml");
Document document = null;
try {
document = saxReader.read(is);
} catch (DocumentException e) {
logger.error(e.getMessage());
throw new RuntimeException("配置文件解析异常" ,e);
}
String xPath = "//constant[@name='" + name + "']";
List<Element> ele = document.selectNodes(xPath);
if(ele != null && ele.size() > 0){
value = ele.get(0).attributeValue("value");
}
return value;
} //读取Action
public static Map<String, ActionConfig> getActions(){
Map<String, ActionConfig> actions = null;
SAXReader saxReader = new SAXReader();
InputStream is = ConfigurationManager.class.getResourceAsStream("/struts.xml");
Document document = null;
try {
document = saxReader.read(is);
} catch (DocumentException e) {
logger.error(e.getMessage());
throw new RuntimeException("配置文件解析异常" ,e);
}
String xPath = "//action";
List<Element> list = document.selectNodes(xPath);
if(list != null && list.size() > 0){
actions = new HashMap<String, ActionConfig>();
for(Element element : list){
ActionConfig actionConfig = new ActionConfig();
String name = element.attributeValue("name");
String method = element.attributeValue("method");
String className = element.attributeValue("class");
Map<String, String> results = null;
List<Element> resultElements = element.elements("result");
if(resultElements != null && resultElements.size() > 0){
results = new HashMap();
for(Element ele: resultElements){
String resultName = ele.attributeValue("name");
String resultValue = ele.getTextTrim();
results.put(resultName, resultValue);
}
}
actionConfig.setName(name);
actionConfig.setMethod(method == null || method.trim().equals("") ? "execute" : method.trim());
actionConfig.setClassName(className);
actionConfig.setResults(results);
actions.put(name, actionConfig);
}
}
return actions;
} }
package cn.itcast.invocation; import cn.itcast.config.ActionConfig;
import cn.itcast.context.ActionContext;
import cn.itcast.interceptor.Interceptor;
import org.apache.log4j.Logger; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List; /**
* Created by zhen on 2017-08-06.
*/
public class ActionInvocation {
private static final Logger logger = Logger.getLogger(ActionInvocation.class);
private Iterator<Interceptor> interceptors;
private Object action;
private ActionConfig actionConfig;
private ActionContext actionContext;
private String resultUrl; public ActionContext getActionContext() {
return actionContext;
} public ActionInvocation(List<String> classNames, ActionConfig actionConfig, HttpServletRequest request, HttpServletResponse response){
//装载Interceptor链
if(classNames != null && classNames.size() > 0){
List<Interceptor> interceptorList = new ArrayList<Interceptor>();
for(String className : classNames){
try {
Interceptor interceptor = (Interceptor) Class.forName(className).newInstance();
interceptor.init();
interceptorList.add(interceptor);
} catch (Exception e) {
logger.error(e.getMessage());
throw new RuntimeException("创建Interceptor失败，Interceptor Name:" + className ,e);
}
}
interceptors = interceptorList.iterator();
} //准备action实例
this.actionConfig = actionConfig;
try {
action = Class.forName(actionConfig.getClassName()).newInstance();
} catch (Exception e) {
logger.error(e.getMessage());
throw new RuntimeException("创建Action实例失败！" + actionConfig.getClass(), e);
} //准备数据中心
actionContext = new ActionContext(request, response, action);
} public String invoke(){
if(interceptors != null && interceptors.hasNext() && resultUrl == null){
Interceptor interceptor = interceptors.next();
resultUrl = interceptor.invoke(this);
}else{
try{
Method executeMethod = Class.forName(actionConfig.getClassName()).getMethod(actionConfig.getMethod());
resultUrl = (String) executeMethod.invoke(action);
}catch(Exception ex){
logger.error(ex.getMessage());
throw new RuntimeException("您配置的action方法不存在" + actionConfig.getClassName());
}
}
return resultUrl;
}
}
package cn.itcast.filter; import cn.itcast.config.ActionConfig;
import cn.itcast.config.ConfigurationManager;
import cn.itcast.context.ActionContext;
import cn.itcast.invocation.ActionInvocation;
import org.apache.log4j.Logger;
import org.junit.Test; import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import java.util.Map; /**
* Created by zhen on 2017-08-06.
*/
public class StrutsPrepareAndExecuteFilter implements Filter {
private static final Logger logger = Logger.getLogger(StrutsPrepareAndExecuteFilter.class);
private List<String> interceptorClassNames;
private String extension;
private Map<String, ActionConfig> actionConfigs; public void init(FilterConfig filterConfig) throws ServletException {
//装载配置信息
interceptorClassNames = ConfigurationManager.getInterceptors();
extension = ConfigurationManager.getConstant("struts.action.extension");
actionConfigs = ConfigurationManager.getActions();
} public static void main(String[] args){
Logger logger = Logger.getLogger(StrutsPrepareAndExecuteFilter.class);
} public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
//执行
HttpServletRequest request = (HttpServletRequest) servletRequest;
HttpServletResponse response = (HttpServletResponse) servletResponse; String urlPath = request.getRequestURI();
if(!urlPath.endsWith(extension)){
filterChain.doFilter(request, response);
return;
}
String actionName = urlPath.substring(urlPath.lastIndexOf("/") + 1).replace("." + extension, "");
ActionConfig actionConfig = actionConfigs.get(actionName);
if(actionConfig == null){
throw new RuntimeException("找不到对应的action！" + actionName);
}
ActionInvocation actionInvocation = new ActionInvocation(interceptorClassNames, actionConfig, request, response);
String result = actionInvocation.invoke();
String dispatcherPath = actionConfig.getResults().get(result);
if(dispatcherPath == null || "".equals(dispatcherPath)){
throw new RuntimeException("找不到对应的返回路径！");
}
request.getRequestDispatcher(dispatcherPath).forward(request, response);
ActionContext.tl.remove();
} public void destroy() { }
}
写后感想：
struts2模拟 1、关注点分离思想。类似java中的解耦合，插拔。将功能拆分成各个拦截器实现。拦截器运行过程中拼接出想要的功能。
2、MVC思想。 filter-C Action-M jsp_url-V 需要掌握知识：
XML解析，Xpath表达式（dom4j）
Servlet技术
java内省（BeanUtils）
ThreadLocal线程本地化类
递归调用 需要补充的知识：
dom4j解析
xpath语法
获取资源文件路径 理解：
对于值栈的模拟不要拘泥于数组，也可以使用现有的类进行封装，比如使用ArrayList模拟。
经常递归调用使用的局部变量可以放在循环外或者说是方法外。
项目路径：
https://github.com/gzdx/MyStruts2.git