设计模式在RESTful当中的应用

第一部分 设计模式概述

企业开发中,除了功能性需求(Functional Requirement)之外,非功能性需求(Non Functional Requirement)也同样重要。在非功能性需求中描述了项目的诸多系统性质量(Systemic Quality)。这些质量包括了灵活性、可维护性、可扩展性。大师编写的代码,质量往往比较高。很多新手在编写项目的同时,bug定位难、经常返工,归根结底在于:不注重设计。

如果新手与大师之间必然要有一道分水岭,那么这一道分水岭,唯系统设计这一个能力,就足以说明问题了。然而 系统设计能力,又应该怎样去提升呢?实际上不论任何行业,学习技能的诀窍不外乎三点: 守、破、离,也就是: 模仿、突破、开拓。那么首先要做的,就是模仿。

所谓设计,我们要模仿的,是前辈们在系统设计时,为我们总结好的经验;以及前辈们在系统设计时,遇到问题后,如何利用模式解决这些问题的。也就是——设计模式。

什么叫设计呢?设计的英文——Design。

  • 在旅游之前,需要规划好出行路线;需要准备好常用药;需要打包好换洗衣服、洗漱化妆用品。

  • 开始一天的工作之前,列好今日工作任务清单

  • 演讲之前,写好草稿

  • ...

以上的这些,都叫做设计。

那么程序员们所说的设计,又是什么呢?这里的设计,即OOD(Object-Oriented Design)——面向对象设计。也就是在实际地编写代码之前,先要规划好思路,不管你的思路到底有没有落到图纸上,哪怕只是打一个腹稿,这也叫做设计!

注: OOD与之对应的又有OOA(Object-Oriented Analysis)——面向对象分析,以及OOP(Object-Oriented Programming)——面向对象编程。它们之间的顺序是: 先分析;再设计;最后编码

什么又叫模式呢?模式的英文——Pattern

  • 当篮球运动员带着篮球,到达了三分线的位置时,为了能够让篮球投到篮框里,手指、手臂将使用多大的力量——这已经形成了他自己的模式
  • 厨师在在做菜时,要先煮米饭,再炒菜;要先把菜、肉、各类食材调料准备好,再热锅放油
  • ...

这些都是生活以及工作、学习中,你去解决某些问题时,所形成的模式。

那么如何一句话概括:什么是模式?模式就是: 通用问题的通用解决方案

RESTful接口,想必大部分的Java程序员都接触过。当我们使用大篇幅的if - else解决问题时、当我们大段大段地复制粘贴我们的代码时,我们有没有思考过,是否可以更优雅地解决这些问题呢?

本篇文章,将籍由常见的RESTful接口,为大家讲解三个设计模式:

  1. 装饰器模式
  2. 策略模式
  3. 简单工厂模式

第二部分 搭建开发环境

本篇使用的项目,将采用Maven + Spring Boot来搭建,其中maven配置文件及Spring Boot启动类如下

  • pom.xml


    4.0.0

    com.itheima
    sample
    1.0-SNAPSHOT

    
        org.springframework.boot
        spring-boot-starter-parent
        2.1.5.RELEASE
    

    
        
            org.springframework.boot
            spring-boot-starter-web
        

        
            org.springframework.boot
            spring-boot-starter-aop
        
    

    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            
        
    

  • Application.java
package com.itheima;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@EnableAutoConfiguration
@ComponentScan
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

第三部分 装饰器模式

1 version 0.1

需求

比如一个系统里有三个接口:

  • /user/login

    登录

  • /user/signout

    注册

  • /user/forget

    忘记密码

对客户端调用后的响应信息来说,不论调用的是哪个方法,系统中都会有两个通用的字段:

  • code

    响应码。

    • 方法执行正确,即为0

    • 方法执行如果出错,即非0值。

    • 客户端在接收到响应码之后,如果是0,走常规流程;如果非0,走异常流程。

  • msg

    响应信息

    • 每个响应码对应一条响应信息。一般情况下是英文。

    • 客户端可以利用国际化技术,将英文转换成中文

    • 响应信息便于客户端调试

设计

基于以上的信息,大部分程序员们的设计将会是这样的:

  1. 在每个ResponseBody里面,都写上两条属性:codemsg
  2. 在每个接口方法里面,手动填充code,及msg

类图

设计模式在RESTful当中的应用_第1张图片
figure_1.png

代码

  • UserController.java
package com.itheima.controller;

import com.itheima.response.ForgetPasswordResp;
import com.itheima.response.LoginResp;
import com.itheima.response.SignoutResp;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping(path = "/user")
public class UserController {

    // 忘记密码接口
    @RequestMapping(path = "/forget_password", method = RequestMethod.POST)
    @ResponseBody
    public ForgetPasswordResp forgetPassword() {
        ForgetPasswordResp result = new ForgetPasswordResp();

        // 业务处理
        // if (用户名不存在) {
        //     result.code = 2230;
        //     result.msg = "user not found";
        //     return result;
        // } else if (...) {
        //     ...
        //     return result;
        // }
        // ...

        result.code = 0;
        result.msg = "success";

        return result;
    }

    // 登录接口
    @RequestMapping(path = "/login", method = RequestMethod.POST)
    @ResponseBody
    public LoginResp login() {
        LoginResp result = new LoginResp();

        // 业务处理
        // if (用户名不存在) {
        //     result.code = 2230;
        //     result.msg = "user not found";
        //     return result;
        // } else if (...) {
        //     ...
        //     return result;
        // }
        // ...

        result.code = 0;
        result.msg = "success";

        return result;
    }

    // 注册接口
    @RequestMapping(path = "/signout", method = RequestMethod.POST)
    @ResponseBody
    public SignoutResp signout() {
        SignoutResp result = new SignoutResp();

        // 业务处理
        // if (用户名不存在) {
        //     result.code = 2230;
        //     result.msg = "user not found";
        //     return result;
        // } else if (...) {
        //     ...
        //     return result;
        // }
        // ...

        result.code = 0;
        result.msg = "success";

        return result;
    }
}
  • ForgetPasswordResp.java
package com.itheima.response;

// 除了msg和code之外,无需向客户端响应任何信息
// 客户端如果接收到了code=0,则默认为接收到了重置密码的邮件
public class ForgetPasswordResp {
    public String msg;
    public int code;

    public ForgetPasswordResp() {
    }

    public ForgetPasswordResp(String msg, int code) {
        this.msg = msg;
        this.code = code;
    }

    @Override
    public String toString() {
        return "ForgetPasswordResp{" +
                "msg='" + msg + '\'' +
                ", code=" + code +
                '}';
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }
}
  • LoginResp.java
package com.itheima.response;

public class LoginResp {
    public String token;
    public String msg;
    public int code;

    public LoginResp() {
    }

    public LoginResp(String token, String msg, int code) {
        this.token = token;
        this.msg = msg;
        this.code = code;
    }

    @Override
    public String toString() {
        return "LoginResp{" +
                "token='" + token + '\'' +
                ", msg='" + msg + '\'' +
                ", code=" + code +
                '}';
    }

    public String getToken() {
        return token;
    }

    public void setToken(String token) {
        this.token = token;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }
}
  • SignoutResp.java
package com.itheima.response;

public class SignoutResp {
    public String token;
    public String msg;
    public int code;

    public SignoutResp() {
    }

    public SignoutResp(String token, String msg, int code) {
        this.token = token;
        this.msg = msg;
        this.code = code;
    }

    @Override
    public String toString() {
        return "SignoutResp{" +
                "token='" + token + '\'' +
                ", msg='" + msg + '\'' +
                ", code=" + code +
                '}';
    }

    public String getToken() {
        return token;
    }

    public void setToken(String token) {
        this.token = token;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }
}

问题

接口约束如果想换成:

  • code为200是正常值
  • msg所对应的信息换成了"operate success"

所有的接口函数都得重新改一遍

2 version 0.2

解决方案

  • 当接口函数没有任何的异常抛出时,即默认为成功。利用Spring切面,对所有的正常返回施加干预
  • codemsg抽离出来,封装成ResponseCommon
  • 所有的Response,复用ResponseCommon。在组合复用与继承复用两个选项中,选择组合复用
  • 使用了组合复用后,会破坏数据结构,利用jackson中的JsonUnwrapped缓解

类图

设计模式在RESTful当中的应用_第2张图片
figure_2.png

代码

  • UserController.java
package com.itheima.controller;

import com.itheima.response.ForgetPasswordResp;
import com.itheima.response.LoginResp;
import com.itheima.response.SignoutResp;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping(path = "/user")
public class UserController {

    @RequestMapping(path = "/forget_password", method = RequestMethod.POST)
    @ResponseBody
    public ForgetPasswordResp forgetPassword() {
        ForgetPasswordResp result = new ForgetPasswordResp();

        // 业务处理

        // 将以下代码删除
        // result.code = 0;
        // result.msg = "success";

        return result;
    }

    @RequestMapping(path = "/login", method = RequestMethod.POST)
    @ResponseBody
    public LoginResp login() {
        LoginResp result = new LoginResp();

        // 业务处理

        // 将以下代码删除
        // result.code = 0;
        // result.msg = "success";

        return result;
    }

    @RequestMapping(path = "/signout", method = RequestMethod.POST)
    @ResponseBody
    public SignoutResp signout() {
        SignoutResp result = new SignoutResp();

        // 业务处理

        // 将以下代码删除
        // result.code = 0;
        // result.msg = "success";
        
        return result;
    }
}
  • ForgetPasswordResp.java
package com.itheima.response;

// 除了msg和code之外,无需向客户端响应任何信息
// 客户端如果接收到了code=0,则默认为接收到了重置密码的邮件
public class ForgetPasswordResp {
    public ResponseCommon responseCommon;

    public ForgetPasswordResp() {
    }

    public ForgetPasswordResp(ResponseCommon responseCommon) {
        this.responseCommon = responseCommon;
    }

    @Override
    public String toString() {
        return "ForgetPasswordResp{" +
                "responseCommon=" + responseCommon +
                '}';
    }

    public ResponseCommon getResponseCommon() {
        return responseCommon;
    }

    public void setResponseCommon(ResponseCommon responseCommon) {
        this.responseCommon = responseCommon;
    }
}
  • LoginResp.java
package com.itheima.response;

public class LoginResp {
    public String token;
    public ResponseCommon responseCommon;

    public LoginResp() {
    }

    public LoginResp(String token, ResponseCommon responseCommon) {
        this.token = token;
        this.responseCommon = responseCommon;
    }

    @Override
    public String toString() {
        return "LoginResp{" +
                "token='" + token + '\'' +
                ", responseCommon=" + responseCommon +
                '}';
    }

    public String getToken() {
        return token;
    }

    public void setToken(String token) {
        this.token = token;
    }

    public ResponseCommon getResponseCommon() {
        return responseCommon;
    }

    public void setResponseCommon(ResponseCommon responseCommon) {
        this.responseCommon = responseCommon;
    }
}
  • SignoutResp.java
package com.itheima.response;

public class SignoutResp {
    public String token;
    public ResponseCommon respnoseCommon;

    public SignoutResp() {
    }

    public SignoutResp(String token, ResponseCommon respnoseCommon) {
        this.token = token;
        this.respnoseCommon = respnoseCommon;
    }

    @Override
    public String toString() {
        return "SignoutResp{" +
                "token='" + token + '\'' +
                ", respnoseCommon=" + respnoseCommon +
                '}';
    }

    public String getToken() {
        return token;
    }

    public void setToken(String token) {
        this.token = token;
    }

    public ResponseCommon getRespnoseCommon() {
        return respnoseCommon;
    }

    public void setRespnoseCommon(ResponseCommon respnoseCommon) {
        this.respnoseCommon = respnoseCommon;
    }
}
  • ResponseCommon.java
package com.itheima.response;

public class ResponseCommon {
    private String msg;
    private int code;

    public ResponseCommon() {
    }

    public ResponseCommon(String msg, int code) {
        this.msg = msg;
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }
}
  • ResponseCommoneAssembler.java
package com.itheima.config;

import java.lang.reflect.Field;

import com.itheima.response.ResponseCommon;
import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.util.ReflectionUtils;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

@ControllerAdvice
public class ResponseCommonAssembler implements ResponseBodyAdvice {

    @Override
    public boolean supports(MethodParameter returnType, Class> converterType) {
        if (returnType.getMethod().getReturnType().equals(void.class)) {
            return true;
        }

        Field[] fields = returnType.getMethod().getReturnType().getDeclaredFields();
        for (Field fieldItem : fields) {
            if (fieldItem.getType().equals(ResponseCommon.class)) {
                return true;
            }
        }

        return false;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,
                                  Class> selectedConverterType, ServerHttpRequest request,
                                  ServerHttpResponse response) {
        Field[] fields = returnType.getMethod().getReturnType().getDeclaredFields();
        for (Field fieldItem : fields) {
            if (fieldItem.getType().equals(ResponseCommon.class)) {
                fieldItem.setAccessible(true);
                ResponseCommon responseCommon = (ResponseCommon) ReflectionUtils.getField(fieldItem, body);
                if (responseCommon == null) {
                    responseCommon = new ResponseCommon();
                    ReflectionUtils.setField(fieldItem, body, responseCommon);
                }
                if (responseCommon.getCode() == 0) {
                    responseCommon.setMsg("success");
                }
            }
        }

        return body;
    }
}
 
 

问题

回过头再查看一下ForgetPasswordResp.java,除了一个responseCommon属性之外,再无其它;对于UserController.java中的forgetPassword接口方法,也无需处理其他的业务。非要给它安排一个ForgetPasswordResp响应体,是不是多此一举?

3 version 0.3

按正常的套路,把方法的返回值改成void就可以了。但是在ResponseCommonAssembler中,我们响应体所有的属性,找到ResponseCommon字段,再将0success填充进去。把响应体改成了void之后,就没有ResponseCommon字段了,怎么玩?

解决方案

ResponseCommonAssembler中,添加"函数返回类型是否为void"的条件判断,直接创建一个新的ResponseCommon对象,将code填充为0,将msg填充为"success",并将这个对象直接返回。

代码

  • UserController.java
package com.itheima.controller;

import com.itheima.response.ForgetPasswordResp;
import com.itheima.response.LoginResp;
import com.itheima.response.SignoutResp;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping(path = "/user")
public class UserController {

    @RequestMapping(path = "/forget_password", method = RequestMethod.POST)
    @ResponseBody
    public void forgetPassword() {

        // 业务处理

        // 将以下代码删除
        // result.code = 0;
        // result.msg = "success";
    }

    @RequestMapping(path = "/login", method = RequestMethod.POST)
    @ResponseBody
    public LoginResp login() {
        LoginResp result = new LoginResp();

        // 业务处理

        // 将以下代码删除
        // result.code = 0;
        // result.msg = "success";

        return result;
    }

    @RequestMapping(path = "/signout", method = RequestMethod.POST)
    @ResponseBody
    public SignoutResp signout() {
        SignoutResp result = new SignoutResp();

        // 业务处理

        // 将以下代码删除
        // result.code = 0;
        // result.msg = "success";

        return result;
    }
}
  • ResponseCommonAssembler.java
package com.itheima.config;

import java.lang.reflect.Field;

import com.itheima.response.ResponseCommon;
import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.util.ReflectionUtils;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

@ControllerAdvice
public class ResponseCommonAssembler implements ResponseBodyAdvice {

    @Override
    public boolean supports(MethodParameter returnType, Class> converterType) {
        if (returnType.getMethod().getReturnType().equals(void.class)) {
            return true;
        }

        Field[] fields = returnType.getMethod().getReturnType().getDeclaredFields();
        for (Field fieldItem : fields) {
            if (fieldItem.getType().equals(ResponseCommon.class)) {
                return true;
            }
        }

        return false;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,
                                  Class> selectedConverterType, ServerHttpRequest request,
                                  ServerHttpResponse response) {
        if (returnType.getMethod().getReturnType().equals(void.class)) {
            ResponseCommon responseCommon = new ResponseCommon();
            responseCommon.setMsg("success");
            return responseCommon;
        }

        Field[] fields = returnType.getMethod().getReturnType().getDeclaredFields();
        for (Field fieldItem : fields) {
            if (fieldItem.getType().equals(ResponseCommon.class)) {
                fieldItem.setAccessible(true);
                ResponseCommon responseCommon = (ResponseCommon) ReflectionUtils.getField(fieldItem, body);
                if (responseCommon == null) {
                    responseCommon = new ResponseCommon();
                    ReflectionUtils.setField(fieldItem, body, responseCommon);
                }
                if (responseCommon.getCode() == 0) {
                    responseCommon.setMsg("success");
                }
            }
        }

        return body;
    }
}
 
 

4 version 1.0

现在的问题是,我们并不能保证,客户端的每一次请求,都会得到一个成功的响应。那么当用户请求出问题时,又该如何解决呢?

解决方案

  • 异常,并不是系统或者框架才能够使用的。当用户请求后,参数填写错误用户名不存在等错误亦可使用异常机制处理。

  • 依然利用Spring切面,对所有的异常返回施加干预

代码

  • GlobalExceptionHandler.java
package com.itheima.config;

import com.itheima.exception.ExceptionCommon;
import com.itheima.response.ResponseCommon;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;

/**
 * 异常拦截器
 *
 */
@ControllerAdvice
public class GlobalExceptionHandler {
    private final static Logger logger = LoggerFactory.getLogger(GlobalExceptionHandler.class);

    /**
     * 自定义异常
     *
     * @see com.itheima.exception.*
     * @param req
     * @param e
     * @return
     */
    @ExceptionHandler(value = ExceptionCommon.class)
    @ResponseBody
    public ResponseCommon commonExceptionHandler(HttpServletRequest req, ExceptionCommon e) {
        return e.getResponseCommon();
    }
}
  • ExceptionCommon.java
package com.itheima.exception;

import com.itheima.response.ResponseCommon;

public class ExceptionCommon extends Exception {
    private static final long serialVersionUID = 3867913775058901502L;

    private ResponseCommon responseCommon;

    public ExceptionCommon() {
        super();
    }

    public ExceptionCommon(ResponseCommon responseCommon) {
        super();
        this.responseCommon = responseCommon;
    }

    public ExceptionCommon(Integer respCode, String respMsg) {
        super();
        responseCommon = new ResponseCommon();
        responseCommon.setCode(respCode);
        responseCommon.setMsg(respMsg);
    }

    public ResponseCommon getResponseCommon() {
        return responseCommon;
    }

    public void setResponseCommon(ResponseCommon responseCommon) {
        this.responseCommon = responseCommon;
    }
}
  • UserController.java
package com.itheima.controller;

import com.itheima.response.ForgetPasswordResp;
import com.itheima.response.LoginResp;
import com.itheima.response.SignoutResp;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping(path = "/user")
public class UserController {

    @RequestMapping(path = "/forget_password", method = RequestMethod.POST)
    @ResponseBody
    public void forgetPassword() throws ExceptionCommon {

        // 异常校验,如果校验失败,则抛出异常

        // 业务处理
    }

    @RequestMapping(path = "/login", method = RequestMethod.POST)
    @ResponseBody
    public LoginResp login() throws ExceptionCommon {
        LoginResp result = new LoginResp();

        // 异常校验,如果校验失败,则抛出异常

        // 业务处理

        return result;
    }

    @RequestMapping(path = "/signout", method = RequestMethod.POST)
    @ResponseBody
    public SignoutResp signout() throws ExceptionCommon {
        SignoutResp result = new SignoutResp();

        // 异常校验,如果校验失败,则抛出异常

        // 业务处理

        return result;
    }
}

5 装饰器模式

科普一下装饰器模式吧

动态地给一个对象添加一些额外的职责。——《设计模式 - 可复用面向对象软件的基础》

第四部分 策略模式 & 简单工厂

1 version 0.1

需求

  • 制作一个企业通讯录,用户可以对通讯录信息进行增删改查

设计

想必大部分的程序员在设计功能的时候,直接把增删改查做成四个接口方法了。设计得再稍微复杂一点,可以批量增、批量删、批量改。

查询功能,用户提交的请求数据,只需要带一个token过来就可以了。所以暂只考虑增、删、改功能

类图

设计模式在RESTful当中的应用_第3张图片
figure_3.png

代码

  • ManageController.java
package com.itheima.controller;

import com.itheima.exception.ExceptionCommon;
import com.itheima.request.Contact;
import com.itheima.request.ContactModifyRequest;
import com.itheima.validation.LogicValidation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping(path = "/manage")
public class ManageController {
    @Autowired
    private UserMapper userMapper;

    @Autowired
    private ContactMapper contactMapper;

    @ResponseBody
    @RequestMapping(path = "/contact_add", method = RequestMethod.POST)
    public void contactAdd(@RequestBody ContactModifyRequest model) throws ExceptionCommon {
        User user = userMapper.queryByToken(model.getUserToken());

        // 判断用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserNotNull(user);

        // 判断用户是管理员,若不是管理员,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserIsManager(user);

        for (Contact contact : model.getContacts()) {
            // 判断被添加的用户不存在,若已存在,则抛异常(由LogicValidation负责抛异常)
            LogicValidation.validateContactContactIsNull(contact);
            contactMapper.addContact(contact);
        }
    }

    @ResponseBody
    @RequestMapping(path = "/contact_del", method = RequestMethod.POST)
    public void contactDel(@RequestBody ContactModifyRequest model) throws ExceptionCommon {
        User user = userMapper.queryByToken(model.getUserToken());

        // 判断用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserNotNull(user);

        // 判断用户是管理员,若不是管理员,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserIsManager(user);

        for (Contact contact : model.getContacts()) {
            // 判断被添加的用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
            LogicValidation.validateContactContactNotNull(contact);
            contactMapper.delContact(contact);
        }
    }

    @ResponseBody
    @RequestMapping(path = "/contact_mod", method = RequestMethod.POST)
    public void contactMod(@RequestBody ContactModifyRequest model) throws ExceptionCommon {
        User user = userMapper.queryByToken(model.getUserToken());

        // 判断用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserNotNull(user);

        // 判断用户是管理员,若不是管理员,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserIsManager(user);

        for (Contact contact : model.getContacts()) {
            // 判断被添加的用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
            LogicValidation.validateContactContactNotNull(contact);
            contactMapper.modContact(contact);
        }
    }
}
  • Contact.java
package com.itheima.request;

public class Contact {
    private String contactId;
    private String mobile;
    private String email;
    private String avatar;
    private String birthday;
    private String birthplace;

    public Contact() {
    }

    @Override
    public String toString() {
        return "Contact{" +
                "userId='" + contactId + '\'' +
                ", mobile='" + mobile + '\'' +
                ", email='" + email + '\'' +
                ", avatar='" + avatar + '\'' +
                ", birthday='" + birthday + '\'' +
                ", birthplace='" + birthplace + '\'' +
                '}';
    }

    public String getContactId() {
        return contactId;
    }

    public void setContactId(String contactId) {
        this.contactId = contactId;
    }

    public String getMobile() {
        return mobile;
    }

    public void setMobile(String mobile) {
        this.mobile = mobile;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getAvatar() {
        return avatar;
    }

    public void setAvatar(String avatar) {
        this.avatar = avatar;
    }

    public String getBirthday() {
        return birthday;
    }

    public void setBirthday(String birthday) {
        this.birthday = birthday;
    }

    public String getBirthplace() {
        return birthplace;
    }

    public void setBirthplace(String birthplace) {
        this.birthplace = birthplace;
    }
}
  • ContactModifyRequest.java
package com.itheima.request;

import java.util.List;

public class ContactModifyRequest {
    private String token;
    private List contacts;

    public ContactModifyRequest() {
    }

    public ContactModifyRequest(String token, List contacts) {
        this.token = token;
        this.contacts = contacts;
    }

    @Override
    public String toString() {
        return "ContactModifyRequest{" +
                "token='" + token + '\'' +
                ", contacts=" + contacts +
                '}';
    }

    public String getToken() {
        return token;
    }

    public void setToken(String token) {
        this.token = token;
    }

    public List getContacts() {
        return contacts;
    }

    public void setContacts(List contacts) {
        this.contacts = contacts;
    }
}

2 version 0.2

问题

  1. 对于客户端,通讯录信息的增删改,完全可以调用同一个接口。目前让客户端调用了多个接口
  2. 对于服务端,增删改接口的大部分业务代码是重合的。完全可以合并到一起

解决方案

  • 在Contact类中,添加一个枚举值,由客户端决定:此条Contact是添加、还是修改、或者删除
  • 在ManageController中,合并增、删、改的接口方法为一个
  • 在ManageController中,遍历Contact,判断枚举是什么,进入增删改流程

设计

设计模式在RESTful当中的应用_第4张图片
figure_4.png

代码

  • Contact.java
package com.itheima.request;

public class Contact {
    private String contactId;
    private String mobile;
    private String email;
    private String avatar;
    private String birthday;
    private String birthplace;
    private String operationType;

    public Contact() {
    }

    @Override
    public String toString() {
        return "Contact{" +
                "userId='" + contactId + '\'' +
                ", mobile='" + mobile + '\'' +
                ", email='" + email + '\'' +
                ", avatar='" + avatar + '\'' +
                ", birthday='" + birthday + '\'' +
                ", birthplace='" + birthplace + '\'' +
                ", operationType='" + operationType + '\'' +
                '}';
    }

    public String getContactId() {
        return contactId;
    }

    public void setContactId(String contactId) {
        this.contactId = contactId;
    }

    public String getMobile() {
        return mobile;
    }

    public void setMobile(String mobile) {
        this.mobile = mobile;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getAvatar() {
        return avatar;
    }

    public void setAvatar(String avatar) {
        this.avatar = avatar;
    }

    public String getBirthday() {
        return birthday;
    }

    public void setBirthday(String birthday) {
        this.birthday = birthday;
    }

    public String getBirthplace() {
        return birthplace;
    }

    public void setBirthplace(String birthplace) {
        this.birthplace = birthplace;
    }

    public String getOperationType() {
        return operationType;
    }

    public void setOperationType(String operationType) {
        this.operationType = operationType;
    }
}
  • ManageController.java
package com.itheima.controller;

import com.itheima.exception.ExceptionCommon;
import com.itheima.request.Contact;
import com.itheima.request.ContactModifyRequest;
import com.itheima.validation.LogicValidation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping(path = "/manage")
public class ManageController {
    @Autowired
    private UserMapper userMapper;

    @Autowired
    private ContactMapper contactMapper;

    @ResponseBody
    @RequestMapping(path = "/contact_mod", method = RequestMethod.POST)
    public void contactMod(@RequestBody ContactModifyRequest model) throws ExceptionCommon {
        User user = userMapper.queryByToken(model.getUserToken());

        // 判断用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserNotNull(user);

        // 判断用户是管理员,若不是管理员,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserIsManager(user);

        for (Contact contact : model.getContacts()) {
            if (contact.getOperationType().equals("add")) {
                // 判断被添加的用户不存在,若已存在,则抛异常(由LogicValidation负责抛异常)
                LogicValidation.validateContactContactIsNull(contact);
                contactMapper.addContact(contact);
            } else if (contact.getOperationType().equals("del")) {
                // 判断被添加的用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
                LogicValidation.validateContactContactNotNull(contact);
                contactMapper.delContact(contact);
            } else /* if (contact.getOperationType().equals("mod")) */ {
                // 判断被添加的用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
                LogicValidation.validateContactContactNotNull(contact);
                contactMapper.modContact(contact);
            }
        }
    }
}

3 version 0.3

问题

  • if - else搞得这么多,菜鸟们总是很愿意这么搞,经常会一个方法写得很长。可维护性、可读性都会很差。

解决方案

  1. 利用策略模式,将每一个条件分支封装成策略。

  2. 利用简单工厂模式,由所有策略类的父类,根据操作类别,创建具体策略。

类图

设计模式在RESTful当中的应用_第5张图片
figure_5.png

代码

  • ManageController.java
package com.itheima.controller;

import com.itheima.controller.strategy.AbstractContactModifyStrategy;
import com.itheima.exception.ExceptionCommon;
import com.itheima.request.Contact;
import com.itheima.request.ContactModifyRequest;
import com.itheima.validation.LogicValidation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping(path = "/manage")
public class ManageController {
    @Autowired
    private UserMapper userMapper;

    @Autowired
    private ContactMapper contactMapper;

    @ResponseBody
    @RequestMapping(path = "/contact_mod", method = RequestMethod.POST)
    public void contactMod(@RequestBody ContactModifyRequest model) throws ExceptionCommon {
        User user = userMapper.queryByToken(model.getUserToken());

        // 判断用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserNotNull(user);

        // 判断用户是管理员,若不是管理员,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateUserIsManager(user);

        for (Contact contact : model.getContacts()) {
            AbstractContactModifyStrategy strategy = AbstractContactModifyStrategy.strategyWithOperationType(contact.getOperationType());
            strategy.operate(contact);
        }
    }
}
  • AbstractContactModifyStrategy.java
package com.itheima.controller.strategy;

import com.itheima.request.Contact;

public abstract class AbstractContactModifyStrategy {
    public final static AbstractContactModifyStrategy strategyWithOperationType(String operationType) throws ExceptionCommon {
        if (operationType.equals("add")) {
            return new AbstractContactAddStrategy();
        } else if (operationType.equals("del")) {
            return new AbstractContactDelStrategy();
        } else /* if (operationType.equals("mod")) */ {
            return new AbstractContactModStrategy();
        }
    }

    public abstract void operate(Contact contact);
}
  • ContactAddStrategy.java
package com.itheima.controller.strategy;

import com.itheima.request.Contact;
import com.itheima.validation.LogicValidation;
import org.springframework.beans.factory.annotation.Autowired;

public class ContactAddStrategy extends AbstractContactModifyStrategy {
    @Autowired
    private ContactMapper contactMapper;

    @Override
    public void operate(Contact contact) throws ExceptionCommon {
        // 判断被添加的用户不存在,若已存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateContactContactIsNull(contact);
        contactMapper.addContact(contact);
    }
}
  • ContactDelStrategy.java
package com.itheima.controller.strategy;

import com.itheima.request.Contact;
import com.itheima.validation.LogicValidation;
import org.springframework.beans.factory.annotation.Autowired;

public class ContactDelStrategy extends AbstractContactModifyStrategy {
    @Autowired
    private ContactMapper contactMapper;

    @Override
    public void operate(Contact contact) throws ExceptionCommon {
        // 判断被添加的用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateContactContactNotNull(contact);
        contactMapper.delContact(contact);
    }
}
  • ContactModStrategy.java
package com.itheima.controller.strategy;

import com.itheima.request.Contact;
import com.itheima.validation.LogicValidation;
import org.springframework.beans.factory.annotation.Autowired;

public class ContactModStrategy extends AbstractContactModifyStrategy {
    @Autowired
    private ContactMapper contactMapper;

    @Override
    public void operate(Contact contact) throws ExceptionCommon {
        // 判断被添加的用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateContactContactNotNull(contact);
        contactMapper.modContact(contact);
    }
}

4 version 1.0

问题

  • 虽然在ManageController当中,不需要写长段的if - else条件判断了。但是依然把if - else延迟到了AbstractContactModifyStrategy当中。即: 每添加一个策略,都需要对AbstractContactModifyStrategy进行修改

解决方案

  1. 在AbstractContactModifyStrategy当中,添加一个注册方法,每个AbstractContactModifyStrategy的子类,都需要调用这一个注册方法。将具体的实现类注册到AbstractContactModifyStrategy当中。
  2. 对于每个具体的策略类,添加static静态方法。在static静态方法中,调用父类的注册方法,将自己注册进父类中
  3. static静态方法只在类加载的时候才会被调用,因为本次项目使用的是Spring-Boot,直接添加类注解@Component,当Spring扫描到此组件时,会自动加载这个类。这个类的static就会被执行了

代码

  • AbstractContactModifyStrategy.java
package com.itheima.controller.strategy;

import com.itheima.request.Contact;
import org.springframework.stereotype.Component;

import java.util.HashMap;
import java.util.Map;

@Component
public abstract class AbstractContactModifyStrategy {
    private static Map> map = new HashMap<>();

    public final static AbstractContactModifyStrategy strategyWithOperationType(String operationType) throws IllegalAccessException, InstantiationException {
        return map.get(operationType).newInstance();
    }

    public final static void registerClass(String operateType, Class clz) {
        map.put(operateType, clz);
    }

    public abstract void operate(Contact contact);
}
  • ContactAddStrategy.java
package com.itheima.controller.strategy;

import com.itheima.request.Contact;
import com.itheima.validation.LogicValidation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class ContactAddStrategy extends AbstractContactModifyStrategy {
    @Autowired
    private ContactMapper contactMapper;

    @Override
    public void operate(Contact contact) {
        // 判断被添加的用户不存在,若已存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateContactContactIsNull(contact);
        contactMapper.addContact(contact);
    }

    static {
        AbstractContactModifyStrategy.registerClass("add", ContactAddStrategy.class);
    }
}
  • ContactDelStrategy.java
package com.itheima.controller.strategy;

import com.itheima.request.Contact;
import com.itheima.validation.LogicValidation;
import org.springframework.beans.factory.annotation.Autowired;

public class ContactDelStrategy extends AbstractContactModifyStrategy {
    @Autowired
    private ContactMapper contactMapper;

    @Override
    public void operate(Contact contact) {
        // 判断被添加的用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateContactContactNotNull(contact);
        contactMapper.delContact(contact);
    }

    static {
        AbstractContactModifyStrategy.registerClass("del", ContactDelStrategy.class);
    }
}
  • ContactModStrategy.java
package com.itheima.controller.strategy;

import com.itheima.request.Contact;
import com.itheima.validation.LogicValidation;
import org.springframework.beans.factory.annotation.Autowired;

public class ContactModStrategy extends AbstractContactModifyStrategy {
    @Autowired
    private ContactMapper contactMapper;

    @Override
    public void operate(Contact contact) {
        // 判断被添加的用户已存在,若不存在,则抛异常(由LogicValidation负责抛异常)
        LogicValidation.validateContactContactNotNull(contact);
        contactMapper.modContact(contact);
    }

    static {
        AbstractContactModifyStrategy.registerClass("mod", ContactModStrategy.class);
    }
}

5 策略模式 & 工厂模式模式

  • 策略模式

定义一系列的算法,把它们一个个封装起来,并且使它们可相互替换。——《设计模式 - 可复用面向对象软件的基础》

  • 简单工厂模式

将“类实例化的操作”与“使用对象的操作”分开,让使用者不用知道具体参数就可以实例化出所需要的“产品”类,从而避免了在客户端代码中显式指定,实现了解耦。

本文中,第二部分 version 0.3,多条if - else,即使用了简单工厂,用于创建策略类。

第五部分 总结

本篇介绍了三个模式: 装饰器模式、策略模式、简单工厂模式

  • 利用装饰器模式,动态地为每一个响应体,添加了code及msg。
    • 异常时,响应体填充code为0; msg为"success"
    • 异常时,为每一个程序内部的异常,取出填充到响应体中
  • 利用策略模式,为通讯录的增、删、改,分别封装了算法。
  • 利用简单工厂模式,根据请求体中的枚举,生产了相应的策略。

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