【问题解决】解决Angular客户端请求Rest服务跨域问题

1.问题描述：通过Origin是http://localhost:4200请求http://localhost:8081的服务，控制台报错如下，但是Response为200。客户端和服务端IP相同，但是端口不同，存在跨域问题。

XMLHttpRequest cannot load http://localhost:8081/api/v1/staffs. No ‘Access-Control-Allow-Origin‘ header is present on the requested resource. Origin ‘http://localhost:4200‘ is therefore not allowed access.

2.解决方法：在服务端/api/v1/staffs的Restful方法增加@CrossOrigin注解，比如：

@CrossOrigin(origins = "*", maxAge = 3600)
@RequestMapping(value = "/api/v1/staffs", produces = { "application/json" }, method = RequestMethod.GET)
RestResponseList<?> queryStaffs(@RequestParam(value = "limit", required = false, defaultValue = "20") int limit,
        @RequestParam(value = "offset", required = false, defaultValue = "0") int offset);

3.重新发送请求http://localhost:8081/api/v1/...，请求成功。且响应头增加了Access-Control-Allow-Credentials和Access-Control-Allow-Origin参数。@CrossOrigin注解即是给响应头增加了这两个参数解决跨域问题。

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4.在服务端POST方法同样使用注解@CrossOrigin解决跨域问题。

@CrossOrigin(origins = "*", maxAge = 3600)
@RequestMapping(value = "/api/v1/staffs", produces = { "application/json" }, method = RequestMethod.POST)
RestResponse<?> createStaff(@RequestBody RestRequest<StaffReqInfo> request);

报错如下：
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5.查看响应码415，错误原因：

"status": 415,
"error": "Unsupported Media Type",
"exception": "org.springframework.web.HttpMediaTypeNotSupportedException",
"message": "Content type ‘text/plain;charset=UTF-8‘ not supported"

6.进一步查看请求头信息，content-type为text/plain。与Response Headers的Content-Type:application/json;charset=UTF-8类型不匹配，故报错。

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7.指定请求头content-type为application/json，比如在Angular中增加Headers。发送Post请求，请求成功。

let headers = new Headers({ ‘Content-Type‘: ‘application/json‘ });
let options = new RequestOptions({ headers });

return this.http.post(this.staffCreateURL, body, options).map((response: Response) => {
    //return this.http.get(this.userLoginURL).map((response:Response)=> {
    let responseInfo = response.json();
    console.log("====请求staffCreateURL成功并返回数据start===");
    console.log(responseInfo);
    console.log("====请求staffCreateURL成功并返回数据end===");
    let staffName = responseInfo.responseInfo.staffName;
    console.log(staffName);
    return responseInfo;
})

另：也可以在HttpServletResponse对象通过setHeader("Access-Control-Allow-Origin", "*")方法增加响应头参数，解决跨域问题，即是@CrossOrigin注解方式。推荐使用注解，方便。