設計模式之責任鏈模式(Chain of Responsibility Pattern)
阿新 • • 發佈：2018-12-18
- 責任鏈模式定義
責任鏈的重點是在“鏈”上，由一條鏈去處理相似的請求在鏈中決定誰來處理這個請求，並返回相應的結果。其定義為：Avoid coupling the sender of a request to its receiver by giving more than one project a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it. 使多個物件都有機會處理請求，從而避免了請求的傳送者和接收者之間的耦合關係。將這些物件連成一條鏈，並沿著這條鏈傳遞改請求，直到有物件處理它為止。 - 責任鏈模式通用類圖
- 責任鏈模式通用程式碼
首先是抽象處理者，①定義一個請求的處理方法handlerMessage。②定義一個鏈的編排方法。③定義具體的請求者必須實現的方法。
public abstract class Handler { private Handler nextHandler; @SuppressWarnings("unlikely-arg-type") public final Response hanleMessage(Request request) { Response response = null; if (this.getHandlerLevel().equals(request.getRequestLevel())) { response = this.echo(request); } else { if(this.nextHandler != null) { response = this.nextHandler.hanleMessage(request); }else { } } return response; } public void setNext(Handler _handler) { this.nextHandler = _handler; } protected abstract Level getHandlerLevel(); protected abstract Response echo(Request request); }
public class Level {
}
public class Request {
public Level getRequestLevel() {
return null;
}
}
public class Response {
}
具體的處理者1
public class ConcreteHandler1 extends Handler { @Override protected Level getHandlerLevel() { // TODO Auto-generated method stub return null; } @Override protected Response echo(Request request) { // TODO Auto-generated method stub return null; } }
具體的處理者2
public class ConcreteHandler2 extends Handler{
@Override
protected Level getHandlerLevel() {
// TODO Auto-generated method stub
return null;
}
@Override
protected Response echo(Request request) {
// TODO Auto-generated method stub
return null;
}
}
具體的處理者3
public class ConcreteHandler3 extends Handler{
@Override
protected Level getHandlerLevel() {
// TODO Auto-generated method stub
return null;
}
@Override
protected Response echo(Request request) {
// TODO Auto-generated method stub
return null;
}
}
呼叫類
public class Client {
public static void main(String[] args) {
// 宣告處理節點
Handler h1 = new ConcreteHandler1();
Handler h2 = new ConcreteHandler2();
Handler h3 = new ConcreteHandler3();
// 處理順序
h1.setNext(h2);
h1.setNext(h3);
// 返回結果
Response response = h1.hanleMessage(new Request());
}
}
- 責任鏈模式例項類圖
其實責任鏈模式在我們工作中還是比較常見的，比如提交請假申請的流程就可以看做一個責任鏈模式，首先老大給批准，接下來經理批准，最後總監批准，這個過程就是一個鏈。
- 責任鏈模式例項程式碼
首先是抽象處理者
public abstract class Handler {
/**
* 持有下一個處理請求的物件
*/
protected Handler successor = null;
/**
* 取值方法
*/
public Handler getSuccessor() {
return successor;
}
/**
* 設定下一個處理請求的物件
*/
public void setSuccessor(Handler successor) {
this.successor = successor;
}
/**
* @return 成功或失敗的具體通知
*/
public abstract String handleRequest(String user, int dayNum);
}
接下來分別是TeamLeader，Manager和GeneralManager
public class TeamLeader extends Handler {
@Override
public String handleRequest(String user, int dayNum) {
String str = "";
// TL許可權比較小
if (dayNum < 3) {
if ("張三".equals(user)) {
str = "成功：TL同意【" + user + "】請假" + dayNum + "天";
} else {
// 其他人一律不同意
str = "其他人一律不同意";
}
} else {
// 請假超過三天的
if (getSuccessor() != null) {
return getSuccessor().handleRequest(user, dayNum);
}
}
return str;
}
}
public class Manager extends Handler{
@Override
public String handleRequest(String user, int dayNum) {
String str = "";
// 經理許可權相對較大
if (dayNum < 5) {
if ("張三".equals(user)) {
str = "成功：經理同意【" + user + "】請假" + dayNum + "天";
} else {
// 其他人一律不同意
str = "其他人一律不同意";
}
} else {
// 請假超過五天的
if (getSuccessor() != null) {
return getSuccessor().handleRequest(user, dayNum);
}
}
return str;
}
}
public class GeneralManager extends Handler {
@Override
public String handleRequest(String user, int dayNum) {
String str = "";
// 總監許可權最大
if (dayNum < 10) {
if ("張三".equals(user)) {
str = "成功：總監同意【" + user + "】請假" + dayNum + "天";
} else {
// 其他人一律不同意
str = "其他人一律不同意";
}
} else {
// 如果還有後繼的處理物件，繼續傳遞
if (getSuccessor() != null) {
return getSuccessor().handleRequest(user, dayNum);
}
}
return str;
}
}
呼叫類
public class Client {
public static void main(String[] args) {
Handler h1 = new TeamLeader();
Handler h2 = new Manager();
Handler h3 = new GeneralManager();
//開始測試
String test1 = h1.handleRequest("張三", 2);
System.out.println("test1 = " + test1);
String test2 = h3.handleRequest("李四", 2);
System.out.println("test2 = " + test2);
System.out.println("---------------------------------------");
String test3 = h2.handleRequest("張三", 4);
System.out.println("test3 = " + test3);
String test4 = h3.handleRequest("李四", 4);
System.out.println("test4 = " + test4);
System.out.println("---------------------------------------");
String test5 = h3.handleRequest("張三", 7);
System.out.println("test5 = " + test5);
String test6 = h3.handleRequest("李四", 7);
System.out.println("test6 = " + test6);
}
}
輸出結果
test1 = 成功：TL同意【張三】請假2天
test2 = 其他人一律不同意
---------------------------------------
test3 = 成功：經理同意【張三】請假4天
test4 = 其他人一律不同意
---------------------------------------
test5 = 成功：總監同意【張三】請假7天
test6 = 其他人一律不同意
參考書籍：設計模式之禪
例項程式碼放在這裡。