责任链模式-Chain of Responsibility
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。
咱们在这里换一个场景:
国王(King类), 经常会遇到各种麻烦(Trouble类), 而国王一旦遇到麻烦, 则会把麻烦交给手下去做.
国王有一天上了战场, 任务法派的顺序是这样的, 骑兵先上, 骑兵不行步兵上, 步兵不行就换贴身侍卫上.
TroubleType枚举
在这里枚举了, 国王在战场上有三种事情会分派给手下去做
public enum TroubleType {
DEFEND, ATTACK, PROTECT
} Trouble类
这里是国王分配的事情
public class Trouble {
private final TroubleType troubleType;
private final String requestDescription;
public Trouble(final TroubleType troubleType, final String requestDescription) {
this.troubleType = Objects.requireNonNull(troubleType);
this.requestDescription = Objects.requireNonNull(requestDescription);
}
public String getRequestDescription() {
return requestDescription;
}
public TroubleType getRequestType() {
return troubleType;
}
@Override
public String toString() {
return getRequestDescription();
}
}Support抽象类
国王的手下解决Trouble都会实现这个Support借口, Support借口是解决Trouble的统一定义
public abstract class Support {
private Support next;
public Support(Support next) {
this.next = next;
}
public void handleRequest(Trouble trouble) {
if (next != null) {
next.handleRequest(trouble);
}
}
protected void printHandling(Trouble trouble) {
System.out.printf("%s 执行任务: %s\n", this, trouble);
}
@Override
public abstract String toString();
}RiderSupport类
骑兵在本例子中只负责进攻
public class RiderSupport extends Support {
public RiderSupport(Support support) {
super(support);
}
@Override
public void handleRequest(Trouble trouble) {
if (trouble.getRequestType().equals(TroubleType.ATTACK)) {
printHandling(trouble);
} else {
super.handleRequest(trouble);
}
}
@Override
public String toString() {
return "Rider";
}
}SolderSupport类
步兵在本例子中只负责防守
public class SolderSupport extends Support {
public SolderSupport(Support support) {
super(support);
}
@Override
public void handleRequest(Trouble trouble) {
if (trouble.getRequestType().equals(TroubleType.DEFEND)) {
printHandling(trouble);
} else {
super.handleRequest(trouble);
}
}
@Override
public String toString() {
return "Soldier";
}
}GuardSupport类
本类负责保卫国王
public class GuardSupport extends Support {
public GuardSupport(Support next) {
super(next);
}
@Override
public void handleRequest(Trouble trouble) {
if (trouble.getRequestType().equals(TroubleType.PROTECT)) {
printHandling(trouble);
} else {
super.handleRequest(trouble);
}
}
@Override
public String toString() {
return "Guard";
}
}King类
本类负责维护责任链.
public class King {
private Support chain;
public King() {
buildChain();
}
private void buildChain() {
chain = new RiderSupport(new SolderSupport(new GuardSupport(null)));
}
public void resolve(Trouble trouble) {
chain.handleRequest(trouble);
}
}Main
运行测试
public class Main {
public static void main(String[] args) {
King king = new King();
king.resolve(new Trouble(TroubleType.DEFEND, "防御"));
king.resolve(new Trouble(TroubleType.ATTACK, "进攻"));
king.resolve(new Trouble(TroubleType.PROTECT, "保护国王"));
}
}