责任链模式-Chain of Responsibility, 例1
在这种模式中，通常每个接收者都包含对另一个接收者的引用。如果一个对象不能处理该请求，那么它会把相同的请求传给下一个接收者，依此类推。
Trouble类
本类是:待责任链来处理的问题Trouble类.
本例子较简单, Trouble只有一个int型作为待处理的编号.
public class Trouble {
private int number;
public Trouble(int number) {
this.number = number;
}
public int getNumber() {
return number;
}
public String toString() {
return "[Trouble " + number + "]";
}
}Support抽象类
Support类是责任链中的节点抽象出来的统一定义.
public abstract class Support {
private String name;
private Support next;
public Support(String name) {
this.name = name;
}
public Support setNext(Support next) {
this.next = next;
return next;
}
protected abstract boolean solve(Trouble trouble);
protected void done(Trouble trouble) { // 解决
System.out.println(trouble + " is resolved by " + this + ".");
}
protected void fail(Trouble trouble) { // 未解决
System.out.println(trouble + " cannot be resolved.");
}
public void execute(Trouble trouble) {
if (solve(trouble)) {
done(trouble);
} else if (next != null) {
next.execute(trouble);
} else {
fail(trouble);
}
}
public String toString() {
return "[" + name + "]";
}
}ZeroSupport类
本类专门用于处理trouble编号为0的
/**
* 本类专门用于处理trouble为0的情况
*/
public class ZeroSupport extends Support {
public ZeroSupport(String name) {
super(name);
} @Override
protected boolean solve(Trouble trouble) {
if (trouble.getNumber() == 0) {
return true;
} else {
return false;
}
}
}
LimitSupport类
只要Trouble的编号小于本类的成员变量limit的值, 那么LimitSupport类的实例就可以处理这个Trouble
/**
* 本类专门用于处理trouble值小于limit的情况
*/
public class LimitSupport extends Support {
private int limit; public LimitSupport(String name, int limit) {
super(name);
this.limit = limit;
} @Override
protected boolean solve(Trouble trouble) {
if (trouble.getNumber() < limit) {
return true;
} else {
return false;
}
}
}
OddSupport类
只要Trouble的编号是奇数, 那么OddSupport类的实例就可以处理这个Trouble.
/**
* 本类专门用于处理trouble为奇数的情况
*/
public class OddSupport extends Support { public OddSupport(String name) {
super(name);
} @Override
protected boolean solve(Trouble trouble) {
if (trouble.getNumber() % 2 == 1) {
return true;
} else {
return false;
}
}
}
Main
用于测试运行
public class Main {
public static void main(String[] args) {
Support charlie = new ZeroSupport("Charlie");
Support bob = new LimitSupport("Bob", 100);
Support diana = new LimitSupport("Diana", 200);
Support elmo = new OddSupport("Elmo");
Support fred = new LimitSupport("Fred", 300);
// 形成职责链
charlie.setNext(bob).setNext(diana).setNext(elmo).setNext(fred);
// 制造各种问题, 并让这个责任链来处理
for (int i = 0; i < 500; i += 33) {
charlie.execute(new Trouble(i));
}
}
}