委派模式
一.委派模式
委派模式:负责任务的调度和分配任务,也就是当任务下来了,找人干活!
二.委派模式-示例
1.新建一IExecute接口,用于下发命令
public interface IExecute {
public void execute(String cmd);
}2.新建一员工A类实现IExecute接口-进行命令的具体实现-只会削苹果
// 该员工只会削苹果
public class EmployeeA implements IExecute {
@Override
public void execute(String cmd) {
System.out.println("员工A"+cmd);
}
}3.新建一员工B类实现IExecute接口-进行命令的具体实现-只会削梨子
// 员工B只会削梨子
public class EmployeeB implements IExecute {
@Override
public void execute(String cmd) {
System.out.println("员工B"+cmd);
}
}
4.新建一领导类实现IExecute接口-进行命令委派
public class Leader implements IExecute{
// 存储 命令-员工 之间的关系
private Map map = new HashMap<>();
public Leader() {
// 让员工A--削苹果
map.put("削苹果",new EmployeeA());
// 让员工B--削梨子
map.put("削梨子",new EmployeeB());
}
@Override
public void execute(String cmd) {
if(map.containsKey(cmd)){
// 根据命令,找到合适的员工,进行执行
map.get(cmd).execute(cmd);
}else{
System.out.println("没有找到可以["+cmd+"]的员工!--需要联系HR进行招聘");
}
}
} 5.新建一测试类
public class Test {
public static void main(String[] args) {
Leader l = new Leader();
l.execute("削苹果");
l.execute("削梨子");
l.execute("剥桔子");
}
}
6.结果
7.关系类图
三.委派模式-在Spring源码中的示例-DispatcherServlet
1.精简后的DispatcherServlet源码
package org.springframework.web.servlet;
/***/
public class DispatcherServlet extends FrameworkServlet {
/***/
private List handlerMappings;
/***/
public DispatcherServlet() {
this.setDispatchOptionsRequest(true);
}
public DispatcherServlet(WebApplicationContext webApplicationContext) {
super(webApplicationContext);
this.setDispatchOptionsRequest(true);
}
/***/
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
if (this.detectAllHandlerMappings) {
Map matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList(matchingBeans.values());
AnnotationAwareOrderComparator.sort(this.handlerMappings);
}
} else {
try {
HandlerMapping hm = (HandlerMapping)context.getBean("handlerMapping", HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
} catch (NoSuchBeanDefinitionException var3) {
;
}
}
if (this.handlerMappings == null) {
this.handlerMappings = this.getDefaultStrategies(context, HandlerMapping.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("No HandlerMappings found in servlet '" + this.getServletName() + "': using default");
}
}
}
/***/
// 通过doDispatch进行请求的转发
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
try {
ModelAndView mv = null;
Object dispatchException = null;
try {
processedRequest = this.checkMultipart(request);
multipartRequestParsed = processedRequest != request;
// 通过getHandler去获取,请求所对应的执行链
mappedHandler = this.getHandler(processedRequest);
if (mappedHandler == null || mappedHandler.getHandler() == null) {
this.noHandlerFound(processedRequest, response);
return;
}
// 通过getHandlerAdapter获取所执行的方式
HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (this.logger.isDebugEnabled()) {
this.logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
}
if ((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {
return;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// 通过mappedHandler.getHandler()==>获取我们所执行的方法(也就是对应的@RequestMapping注解所在的方法)
// 通过HandlerAdapter匹配的对应的执行方式去执行,获得ModelAndView执行返回
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
this.applyDefaultViewName(processedRequest, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv);
} catch (Exception var20) {
dispatchException = var20;
} catch (Throwable var21) {
dispatchException = new NestedServletException("Handler dispatch failed", var21);
}
this.processDispatchResult(processedRequest, response, mappedHandler, mv, (Exception)dispatchException);
} catch (Exception var22) {
this.triggerAfterCompletion(processedRequest, response, mappedHandler, var22);
} catch (Throwable var23) {
this.triggerAfterCompletion(processedRequest, response, mappedHandler, new NestedServletException("Handler processing failed", var23));
}
} finally {
if (asyncManager.isConcurrentHandlingStarted()) {
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
} else if (multipartRequestParsed) {
this.cleanupMultipart(processedRequest);
}
}
}
/***/
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
Iterator var2 = this.handlerMappings.iterator();
HandlerExecutionChain handler;
do {
if (!var2.hasNext()) {
return null;
}
HandlerMapping hm = (HandlerMapping)var2.next();
if (this.logger.isTraceEnabled()) {
this.logger.trace("Testing handler map [" + hm + "] in DispatcherServlet with name '" + this.getServletName() + "'");
}
// 会通过请求中的路径,去匹配到(我们通过@RequestMapping注解所在的方法)
handler = hm.getHandler(request);
} while(handler == null);
return handler;
}
/***/
} 2.对与Spring源码DispatcherServlet-进行粗糙的仿写
1.新建一DispatcherServlet
public class DispatcherServlet {
private List handlerMappings;
private void initHandlerMappings() {
this.handlerMappings = new ArrayList<>();
this.handlerMappings.add(new HandlerMapping("login",new Handler("login()","loginSuccess")));
this.handlerMappings.add(new HandlerMapping("logout",new Handler("logout()","logoutSuccess")));
}
public DispatcherServlet() {
initHandlerMappings();
}
protected void doDispatch(String request){
Handler handler = this.getHandler(request);
System.out.println("执行方法["+handler.getName()+"],获得结果["+handler.getResult()+"]");
}
private Handler getHandler(String request){
Iterator var2 = this.handlerMappings.iterator();
Handler handler;
do {
if (!var2.hasNext()) {
return null;
}
HandlerMapping hm = (HandlerMapping)var2.next();
handler = hm.getHandler(request);
} while(handler == null);
return handler;
}
}
2.新建一HandlerMapping
public class HandlerMapping {
private String method;
private Handler handler;
public HandlerMapping(String method, Handler handler) {
this.method = method;
this.handler = handler;
}
public Handler getHandler(String request){
if (request.equals(this.method)){
return this.handler;
}
return null;
}
}
3.新建一handler
public class Handler {
private String name;
private String result;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getResult() {
return result;
}
public void setResult(String result) {
this.result = result;
}
public Handler(String name, String result) {
this.name = name;
this.result = result;
}
}4.新建一测试类
public class Test {
public static void main(String[] args) {
DispatcherServlet dispatcherServlet = new DispatcherServlet();
dispatcherServlet.doDispatch("login");
dispatcherServlet.doDispatch("logout");
}
}5.测试结果
6.DispatcherServlet类图
