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notes/设计模式.md

@@ -584,7 +584,109 @@ abc
 
 ### 意图
 
-避免将请求的发送者附加到其接收者，从而使其它对象也可以处理请求；将请求以对象的方式发送到链上直到请求被处理完毕。
+使多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系。将这些对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它为止。
+
+### 类图
+
+- Handler：定义处理请求的接口，并且实现后继链（successor）
+
+<div align="center"> <img src="../pics//691f11eb-31a7-46be-9de1-61f433c4b3c7.png"/> </div><br>
+
+### 实现
+
+```java
+public abstract class Handler {
+    protected Handler successor;
+
+    public Handler(Handler successor) {
+        this.successor = successor;
+    }
+
+    protected abstract void handleRequest(Request request);
+}
+```
+
+```java
+public class ConcreteHandler1 extends Handler {
+    public ConcreteHandler1(Handler successor) {
+        super(successor);
+    }
+
+    @Override
+    protected void handleRequest(Request request) {
+        if (request.getType() == RequestType.type1) {
+            System.out.println(request.getName() + " is handle by ConcreteHandler1");
+            return;
+        }
+        if (successor != null) {
+            successor.handleRequest(request);
+        }
+    }
+}
+```
+
+```java
+public class ConcreteHandler2 extends Handler{
+    public ConcreteHandler2(Handler successor) {
+        super(successor);
+    }
+
+    @Override
+    protected void handleRequest(Request request) {
+        if (request.getType() == RequestType.type2) {
+            System.out.println(request.getName() + " is handle by ConcreteHandler2");
+            return;
+        }
+        if (successor != null) {
+            successor.handleRequest(request);
+        }
+    }
+}
+```
+
+```java
+public class Request {
+    private RequestType type;
+    private String name;
+
+    public Request(RequestType type, String name) {
+        this.type = type;
+        this.name = name;
+    }
+
+    public RequestType getType() {
+        return type;
+    }
+
+    public String getName() {
+        return name;
+    }
+}
+```
+
+```java
+public enum RequestType {
+    type1, type2
+}
+```
+
+```java
+public class Client {
+    public static void main(String[] args) {
+        Handler handler1 = new ConcreteHandler1(null);
+        Handler handler2 = new ConcreteHandler2(handler1);
+        Request request1 = new Request(RequestType.type1, "request1");
+        handler2.handleRequest(request1);
+        Request request2 = new Request(RequestType.type2, "request2");
+        handler2.handleRequest(request2);
+    }
+}
+```
+
+```html
+request1 is handle by ConcreteHandler1
+request2 is handle by ConcreteHandler2
+```
 
 ### JDK