java设计模式---职责链模式

职责链的本质：分离职责，动态组合

样例：

/** * 定义职责对象的接口 * */public abstract class Handler {          protected Handler successor;           /**           * 设置下一个处理请求对象           * @param successor           */         public void setSuccessor(Handler successor) {                    this.successor = successor;         }         /**          * 处理聚餐费用的申请          * @param user 申请人          * @param fee 申请的费用          * @return          */        public abstract String handlerFeeRequest(String user, double fee);}

/** * 部门经理审批 * */public class DepManager extends Handler {          @Override          public String handlerFeeRequest(String user, double fee) {                      String str = "";                      if(fee < 1000) {                                 if("Joe".equals(user)) {                                        str = "Department manager agreed " + user + "'s request, the fee is $" + fee;                                 } else {                                        str = "Department manager didn't agree " + user + "'s request.";                                 }                                 return str;                    }                    // more than $1000, next to others.                    if(this.successor != null) {                              return successor.handlerFeeRequest(user, fee);                    }                    return str;         }}/** * 项目经理审批 * */public class ProjectManager extends Handler {          @Override          public String handlerFeeRequest(String user, double fee) {                    String str = "";                      if(fee < 500) {                               if("Joe".equals(user)) {                                      str = "Project manager agreed " + user + "'s request, the fee is $" + fee;                                }  else {                                      str = "Project manager didn't agree " + user + "'s request.";                                }                                return str;                    }                    // more than $500, next to others.                   if(this.successor != null) {                            return successor.handlerFeeRequest(user, fee);                   }                   return str;         }}/** * 总经理审批 * */public class GeneralManager extends Handler {          @Override          public String handlerFeeRequest(String user, double fee) {                    String str = "";                      if(fee >= 1000) {                              if("Joe".equals(user)) {                                         str = "General manager agreed " + user + "'s request, the fee is $" + fee;                              } else {                                         str = "General manager didn't agree " + user + "'s request.";                              }                              return str;                   }                   // next to others.                   if(this.successor != null) {                             return successor.handlerFeeRequest(user, fee);                   }                   return str;          }}

public class Client {           public static void main(String[] args) {                      Handler h1 = new ProjectManager();                      Handler h2 = new DepManager();                      Handler h3 = new GeneralManager();                        h2.setSuccessor(h3);                      h1.setSuccessor(h2);                        String ret1 = h1.handlerFeeRequest("Joe", 300);                      System.out.println(ret1);                      String ret2 = h1.handlerFeeRequest("Yoyo", 300);                      System.out.println(ret2);                        String ret3 = h1.handlerFeeRequest("Joe", 800);                      System.out.println(ret3);                      String ret4 = h1.handlerFeeRequest("Yoyo", 800);                      System.out.println(ret4);                        String ret5 = h1.handlerFeeRequest("Joe", 1300);                      System.out.println(ret5);                      String ret6 = h1.handlerFeeRequest("Yoyo", 1300);                      System.out.println(ret6);          }}