传统的mvc，view的生成其实是在服务器端生成的，或者页面跳转实在服务器端操纵的。
前后端分离，前后端之间的所有交互都是数据。前端自己实现路由，前端需要展示的数据则由后端提供。
之前做过车联网的一个项目。客户端有Android，iOS，PC客户端，浏览器等，使用的是Restful。当时刚毕业，知道这种模式强大，但却不知道这就是前后端分离的一个案例。如下图
rest简介
REST是一种交互方式，Restful则是符合rest原则的风格框架
无状态。每次请求不受上一次或者下一次请求影响
面向资源。这里的资源即数据，事实上，狭义的讲，就是一个URI。
如果一个架构复核REST原则，那么它就是一个Restful框架
共6中请求：PUT DELETE GET POST HEAD OPTIONS
如果URI相同，但是请求方式不同，那么处理的方法也不同
用uri定位资源，用http method定义操作
实现REST架构
1.前端统一返回json数据格式
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{
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success : true,
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message:'',
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code:'',
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data : {}
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}
2.后端统一对应的返回实体
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import org.apache.ibatis.exceptions.TooManyResultsException;
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import java.sql.SQLException;
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/**
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* 增删改时返回前端的判断实体
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* @author Lihhz 2017-03-15
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*
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*/
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public class ResponseState {
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/**错误信息*/
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protected String message;
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/**错误编码*/
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protected short code;
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/**是否成功*/
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protected boolean success;
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/**返回数据*/
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protected Object data;
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public ResponseState() {
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this.code = 0;
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this.success = true;
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this.data = null;
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}
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public ResponseState(String message) {
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this.message = message;
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}
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public ResponseState(short code, String message) {
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this.code = code;
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this.message = message;
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}
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public ResponseState(boolean success, String message) {
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this.success = success;
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this.message = message;
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}
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public ResponseState(short code, boolean success, String message) {
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this.code = code;
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this.success = success;
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this.message = message;
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}
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public ResponseState(Exception ex) {
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this.code = -1;
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this.success = false;
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if (ex.getMessage() == null) {
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this.message = "参数不正确或不完整";
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} else if (ex.getCause() instanceof SQLException)
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this.message = "服务器异常：执行数据库语句错误";
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else if(ex.getCause() instanceof TooManyResultsException)
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this.message = "应该查询出一条结果,但查询出多条结果.";
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else
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setMessage(ex.getMessage());
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}
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public String getMessage() {
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return this.message;
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}
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public void setMessage(String message) {
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if (message != null)
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message = message.replace("\"", "'").replace('\r', '\0');
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this.message = message;
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}
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public short getCode() {
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return this.code;
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}
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public void setCode(short code) {
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this.code = code;
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}
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public boolean getSuccess() {
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return this.success;
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}
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public void setSuccess(boolean success) {
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this.success = success;
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}
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public Object getData() {
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return this.data;
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}
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public void setData(Object data) {
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this.data = data;
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}
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public String toString() {
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StringBuffer sbJson = new StringBuffer("{\"code\":");
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sbJson.append(this.code).append(",\"message\":\"").append(this.message)
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.append("\",").append("\"success\":").append(this.success)
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.append("}");
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return sbJson.toString();
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}
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}
3.数据格式转换
前端的json如何转化为后端的entity，后端的entity又如何转前端json
在spring mvc中提供一种转换方式
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@ResponseBody
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@RequestMapping(value = "/query", method = RequestMethod.POST)
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public PageVO query(HttpServletRequest request) {
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……
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}
其中RequestBody负责前端数据转后端，而ResponseBody则反之。如果使用@RestController而不是@Controller则不需要在方法上使用ResponseBody。下边是RestController的源码
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/*
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* Copyright 2002-2014 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.web.bind.annotation;
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import java.lang.annotation.Documented;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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import org.springframework.stereotype.Controller;
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/**
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* A convenience annotation that is itself annotated with {@link Controller @Controller}
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* and {@link ResponseBody @ResponseBody}.
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* <p>
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* Types that carry this annotation are treated as controllers where
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* {@link RequestMapping @RequestMapping} methods assume
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* {@link ResponseBody @ResponseBody} semantics by default.
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*
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* @author Rossen Stoyanchev
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* @author Sam Brannen
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* @since 4.0
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*/
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@Target(ElementType.TYPE)
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@Retention(RetentionPolicy.RUNTIME)
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@Documented
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@Controller
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@ResponseBody
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public @interface RestController {
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/**
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* The value may indicate a suggestion for a logical component name,
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* to be turned into a Spring bean in case of an autodetected component.
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* @return the suggested component name, if any
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* @since 4.0.1
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*/
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String value() default "";
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}
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在spring中配置jackson进行json的序列化操作
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<bean id="dateFormat" class="java.text.SimpleDateFormat">
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<constructor-arg value="yyyy-MM-dd HH:mm:ss" />
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</bean>
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<!-- 也可以自定义ObjectMapper继承自org.codehaus.jackson.map.ObjectMapper,做一些特殊处理。-->
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<bean id="objectMapper" class="org.codehaus.jackson.map.ObjectMapper">
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<property name="dateFormat" ref="dateFormat" />
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</bean>
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<!-- 注册RequestMappingHandlerMapping 和RequestMappingHandlerAdapter 两个bean。-->
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<mvc:annotation-driven>
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<mvc:message-converters>
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<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
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<property name="objectMapper" ref="objectMapper">
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</property>
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</bean>
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</mvc:message-converters>
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</mvc:annotation-driven>
至此，一个简单的Restful风格的框架就搭建起来了。还有安全验证，异常处理，跨域等问题需要处理。
