spring boot实现超轻量级网关的方法(反向代理、转发)
在我们的rest服务中，需要暴露一个中间件的接口给用户，但是需要经过rest服务的认证，这是典型的网关使用场景。可以引入网关组件来搞定，但是引入zuul等中间件会增加系统复杂性，这里实现一个超轻量级的网关，只实现请求转发，认证等由rest服务的springsecurity来搞定。
如何进行请求转发呢？熟悉网络请求的同学应该很清楚，请求无非就是请求方式、HTTPheader，以及请求body，我们将这些信息取出来，透传给转发的url即可。
举例：
/graphdb/**转发到Graph_Server/**
获取转发目的地址：
privateStringcreateRedictUrl(HttpServletRequestrequest,StringrouteUrl,Stringprefix){
StringqueryString=request.getQueryString();
returnrouteUrl+request.getRequestURI().replace(prefix,"")+
(queryString!=null?"?"+queryString:"");
}
解析请求头和内容
然后从request中提取出header、body等内容，构造一个RequestEntity，后续可以用RestTemplate来请求。
privateRequestEntitycreateRequestEntity(HttpServletRequestrequest,Stringurl)throwsURISyntaxException,IOException{
Stringmethod=request.getMethod();
HttpMethodhttpMethod=HttpMethod.resolve(method);
MultiValueMapheaders=parseRequestHeader(request);
byte[]body=parseRequestBody(request);
returnnewRequestEntity<>(body,headers,httpMethod,newURI(url));
}
privatebyte[]parseRequestBody(HttpServletRequestrequest)throwsIOException{
InputStreaminputStream=request.getInputStream();
returnStreamUtils.copyToByteArray(inputStream);
}
privateMultiValueMapparseRequestHeader(HttpServletRequestrequest){
HttpHeadersheaders=newHttpHeaders();
ListheaderNames=Collections.list(request.getHeaderNames());
for(StringheaderName:headerNames){
ListheaderValues=Collections.list(request.getHeaders(headerName));
for(StringheaderValue:headerValues){
headers.add(headerName,headerValue);
}
}
returnheaders;
}
透明转发
最后用RestTemplate来实现请求：
privateResponseEntityroute(RequestEntityrequestEntity){ RestTemplaterestTemplate=newRestTemplate(); returnrestTemplate.exchange(requestEntity,String.class); }
全部代码
以下是轻量级转发全部代码：
importorg.springframework.http.*;
importorg.springframework.stereotype.Service;
importorg.springframework.util.MultiValueMap;
importorg.springframework.util.StreamUtils;
importorg.springframework.web.client.RestTemplate;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
importjava.io.IOException;
importjava.io.InputStream;
importjava.net.URI;
importjava.net.URISyntaxException;
importjava.util.Collections;
importjava.util.List;
@Service
publicclassRoutingDelegate{
publicResponseEntityredirect(HttpServletRequestrequest,HttpServletResponseresponse,StringrouteUrl,Stringprefix){
try{
//builduptheredirectURL
StringredirectUrl=createRedictUrl(request,routeUrl,prefix);
RequestEntityrequestEntity=createRequestEntity(request,redirectUrl);
returnroute(requestEntity);
}catch(Exceptione){
returnnewResponseEntity("REDIRECTERROR",HttpStatus.INTERNAL_SERVER_ERROR);
}
}
privateStringcreateRedictUrl(HttpServletRequestrequest,StringrouteUrl,Stringprefix){
StringqueryString=request.getQueryString();
returnrouteUrl+request.getRequestURI().replace(prefix,"")+
(queryString!=null?"?"+queryString:"");
}
privateRequestEntitycreateRequestEntity(HttpServletRequestrequest,Stringurl)throwsURISyntaxException,IOException{
Stringmethod=request.getMethod();
HttpMethodhttpMethod=HttpMethod.resolve(method);
MultiValueMapheaders=parseRequestHeader(request);
byte[]body=parseRequestBody(request);
returnnewRequestEntity<>(body,headers,httpMethod,newURI(url));
}
privateResponseEntityroute(RequestEntityrequestEntity){
RestTemplaterestTemplate=newRestTemplate();
returnrestTemplate.exchange(requestEntity,String.class);
}
privatebyte[]parseRequestBody(HttpServletRequestrequest)throwsIOException{
InputStreaminputStream=request.getInputStream();
returnStreamUtils.copyToByteArray(inputStream);
}
privateMultiValueMapparseRequestHeader(HttpServletRequestrequest){
HttpHeadersheaders=newHttpHeaders();
ListheaderNames=Collections.list(request.getHeaderNames());
for(StringheaderName:headerNames){
ListheaderValues=Collections.list(request.getHeaders(headerName));
for(StringheaderValue:headerValues){
headers.add(headerName,headerValue);
}
}
returnheaders;
}
}
Spring集成
SpringController,RequestMapping里把GET\POST\PUT\DELETE支持的请求带上，就能实现转发了。
@RestController
@RequestMapping(GraphDBController.DELEGATE_PREFIX)
@Api(value="GraphDB",tags={
"graphdb-Api"
})
publicclassGraphDBController{
@Autowired
GraphPropertiesgraphProperties;
publicfinalstaticStringDELEGATE_PREFIX="/graphdb";
@Autowired
privateRoutingDelegateroutingDelegate;
@RequestMapping(value="/**",method={RequestMethod.GET,RequestMethod.POST,RequestMethod.PUT,RequestMethod.DELETE},produces=MediaType.TEXT_PLAIN_VALUE)
publicResponseEntitycatchAll(HttpServletRequestrequest,HttpServletResponseresponse){
returnroutingDelegate.redirect(request,response,graphProperties.getGraphServer(),DELEGATE_PREFIX);
}
}
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