Spring MVC 解决跨域问题&以及对@RequestBody的理解

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Spring MVC 解决跨域问题&以及对@RequestBody的理解

本来想学习一下@RequestBody这个注解，但发请求时出现跨域问题，所以就先来看一下跨域该怎么办。

CORS

首先因为最近在做一个前后端分离的项目，分开就意味着可能不在一个域中，所以不可避免的遇到CORS的问题。试过几个方法：

Spring MVC 4.2.5以后新增的支持跨域的注解@CrossOrigin，如果是老项目的话升级spring库可能会有些兼容的问题，不知为什么这个注解没有升效;
用反向代理，这个一定好使的;

还有就是我现在使用的，手动增加一个Filter，在Response中增加对跨域的支持，这种方式对老浏览器可能会有问题。

CORSFilter.java

public class CORSFilter implements Filter {public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {    HttpServletResponse response = (HttpServletResponse) res;    response.setHeader("Access-Control-Allow-Origin", "*");    response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");    response.setHeader("Access-Control-Max-Age", "3600");    response.addHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");    chain.doFilter(req, res);}public void init(FilterConfig filterConfig) {}public void destroy() {}}

web.xml

<filter>    <filter-name>cors</filter-name>    <filter-class>xxxx.CORSFilter</filter-class></filter><filter-mapping>    <filter-name>cors</filter-name>    <url-pattern>/*</url-pattern></filter-mapping>

如此即可解决跨域问题。

`@RequestBody`

下面说说@RequestBody这个注解。因为一直觉得传简单对象直接不用注解也可以自动组装，就以为spring可以为我们组装所有类型的对象。但今天测试过，原来象Map,List或复合对象都必需使用这个注解才可以正确组装，以下是我的测试代码：
首先写个测试的Controller:

RequestBodyController.java

import java.util.List;import java.util.Map;import javax.servlet.http.HttpServletResponse;import org.cunframework.core.common.controller.BaseController;import org.springframework.context.annotation.Scope;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.CrossOrigin;import org.springframework.web.bind.annotation.RequestBody;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.ResponseBody;import com.alibaba.fastjson.JSON;class A{    private String name;    private String value;    public String getName() {        return name;    }    public String getValue() {        return value;    }    public void setName(String name) {        this.name = name;    }    public void setValue(String value) {        this.value = value;    }}class B{    private List<A> a;    private String count;    public List<A> getA() {        return a;    }    public String getCount() {        return count;    }    public void setA(List<A> a) {        this.a = a;    }    public void setCount(String count) {        this.count = count;    }}@Scope("prototype")@Controller@RequestMapping("/rb")public class RequestBodyController extends BaseController{    @RequestMapping(value = "test1")    @ResponseBody    public Map test1(A a,HttpServletResponse response) {        try {            System.out.println(JSON.toJSONString(a));            return toSuccess();        } catch (Exception e) {            e.printStackTrace();            return toError();        }    }    @RequestMapping(value = "test2")    @ResponseBody    public Map test2(List<A> a,HttpServletResponse response) {        try {            System.out.println(JSON.toJSONString(a));            return toSuccess();        } catch (Exception e) {            e.printStackTrace();            return toError();        }    }    @RequestMapping(value = "test3")    @ResponseBody    public Map test3(@RequestBody List<A> a,HttpServletResponse response) {        try {            System.out.println(JSON.toJSONString(a));            return toSuccess();        } catch (Exception e) {            e.printStackTrace();            return toError();        }    }    @RequestMapping(value = "test4")    @ResponseBody    public Map test4(B b,HttpServletResponse response) {        try {            System.out.println(JSON.toJSONString(b));            return toSuccess();        } catch (Exception e) {            e.printStackTrace();            return toError();        }    }    @RequestMapping(value = "test5")    @ResponseBody    public Map test5(@RequestBody B b,HttpServletResponse response) {        try {            System.out.println(JSON.toJSONString(b));            return toSuccess();        } catch (Exception e) {            e.printStackTrace();            return toError();        }    }}

测试用的html文件：
test.html

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title>Document</title>    <script src="http://lib.sinaapp.com/js/jquery/1.9.1/jquery-1.9.1.min.js"></script>    <script>        function ajax(url,data,contentType){            $.ajax({                type: "POST",                contentType: contentType,                url: url,                data: data,                success: function(data){                    console.log(data);                },                error: function(XMLHttpRequest, textStatus, errorThrown) {                    alert("Error Occured!");                }            });        }        function test1(){            var data = {                name:123,                value:456            };            ajax(                "http://localhost:8080/orcs/rb/test1.do",                data,                "application/x-www-form-urlencoded"            )        }        function test2(){            var data = [                {                    name:123,                    value:456                },                {                    name:222,                    value:222                },                {                    name:333,                    value:444456                }            ];            ajax(                "http://localhost:8080/orcs/rb/test2.do",                data,                "application/x-www-form-urlencoded"            );        }        function test3(){            var data = [                {                    name:123,                    value:456                },                {                    name:222,                    value:222                },                {                    name:333,                    value:444456                }            ];            ajax(                "http://localhost:8080/orcs/rb/test3.do",                JSON.stringify(data),                "application/json"            );        }        function test4(){            var data = {                a:[{                    name:123,                    value:456                },                {                    name:222,                    value:222                },                {                    name:333,                    value:444456                }],                count:222            }            ajax(                "http://localhost:8080/orcs/rb/test4.do",                data,                "application/x-www-form-urlencoded"            );        }        function test5(){            var data = {                a:[{                    name:123,                    value:456                },                {                    name:222,                    value:222                },                {                    name:333,                    value:444456                }],                count:222            };            ajax(                "http://localhost:8080/orcs/rb/test5.do",                JSON.stringify(data),                "application/json"            );        }    </script></head><body>    <button onclick="test1()">btn1</button>    <button onclick="test2()">btn2</button>    <button onclick="test3()">btn3</button>    <button onclick="test4()">btn4</button>    <button onclick="test5()">btn5</button></body></html>

发现@RequestBody这个注解，使用时对ajax有些要求：

数据必需要用JSON.stringify(data)处理;
contentType类型必需为application/json。

而不加这个注解组装简单对象时，则：
1. 数据直接用json不必处理;
2. contentType类型默认为application/x-www-form-urlencoded即可。

因为没有深入研究，有不对的地方请指出 :)

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