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，
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spring security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、HTTP header，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：
private String createRedictUrl(HttpServletRequest request, String routeUrl, String prefix) {
String queryString = request.getQueryString();
return routeUrl + 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。
private RequestEntity createRequestEntity(HttpServletRequest request, String url) throws URISyntaxException, IOException {
String method = request.getMethod();
HttpMethod httpMethod = HttpMethod.resolve(method);
MultiValueMap<String, String> headers = parseRequestHeader(request);
byte[] body = parseRequestBody(request);
return new RequestEntity<>(body, headers, httpMethod, new URI(url));
}
private byte[] parseRequestBody(HttpServletRequest request) throws IOException {
InputStream inputStream = request.getInputStream();
return StreamUtils.copyToByteArray(inputStream);
}
private MultiValueMap<String, String> parseRequestHeader(HttpServletRequest request) {
HttpHeaders headers = new HttpHeaders();
List<String> headerNames = Collections.list(request.getHeaderNames());
for (String headerName : headerNames) {
List<String> headerValues = Collections.list(request.getHeaders(headerName));
for (String headerValue : headerValues) {
headers.add(headerName, headerValue);
}
}
return headers;
}
透明转发
最后用RestTemplate来实现请求：
private ResponseEntity<String> route(RequestEntity requestEntity) {
RestTemplate restTemplate = new RestTemplate();
return restTemplate.exchange(requestEntity, String.class);
}
全部代码
以下是轻量级转发全部代码：
import org.springframework.http.*;
import org.springframework.stereotype.Service;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StreamUtils;
import org.springframework.web.client.RestTemplate;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.Collections;
import java.util.List;
@Service
public class RoutingDelegate {
public ResponseEntity<String> redirect(HttpServletRequest request, HttpServletResponse response,String routeUrl, String prefix) {
try {
// build up the redirect URL
String redirectUrl = createRedictUrl(request,routeUrl, prefix);
RequestEntity requestEntity = createRequestEntity(request, redirectUrl);
return route(requestEntity);
} catch (Exception e) {
return new ResponseEntity("REDIRECT ERROR", HttpStatus.INTERNAL_SERVER_ERROR);
}
}
private String createRedictUrl(HttpServletRequest request, String routeUrl, String prefix) {
String queryString = request.getQueryString();
return routeUrl + request.getRequestURI().replace(prefix, "") +
(queryString != null ? "?" + queryString : "");
}
private RequestEntity createRequestEntity(HttpServletRequest request, String url) throws URISyntaxException, IOException {
String method = request.getMethod();
HttpMethod httpMethod = HttpMethod.resolve(method);
MultiValueMap<String, String> headers = parseRequestHeader(request);
byte[] body = parseRequestBody(request);
return new RequestEntity<>(body, headers, httpMethod, new URI(url));
}
private ResponseEntity<String> route(RequestEntity requestEntity) {
RestTemplate restTemplate = new RestTemplate();
return restTemplate.exchange(requestEntity, String.class);
}
private byte[] parseRequestBody(HttpServletRequest request) throws IOException {
InputStream inputStream = request.getInputStream();
return StreamUtils.copyToByteArray(inputStream);
}
private MultiValueMap<String, String> parseRequestHeader(HttpServletRequest request) {
HttpHeaders headers = new HttpHeaders();
List<String> headerNames = Collections.list(request.getHeaderNames());
for (String headerName : headerNames) {
List<String> headerValues = Collections.list(request.getHeaders(headerName));
for (String headerValue : headerValues) {
headers.add(headerName, headerValue);
}
}
return headers;
}
}
Spring 集成
Spring Controller,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"
})
public class GraphDBController {
@Autowired
GraphProperties graphProperties;
public final static String DELEGATE_PREFIX = "/graphdb";
@Autowired
private RoutingDelegate routingDelegate;
@RequestMapping(value = "/**", method = {RequestMethod.GET, RequestMethod.POST, RequestMethod.PUT, RequestMethod.DELETE}, produces = MediaType.TEXT_PLAIN_VALUE)
public ResponseEntity catchAll(HttpServletRequest request, HttpServletResponse response) {
return routingDelegate.redirect(request, response, graphProperties.getGraphServer(), DELEGATE_PREFIX);
}
}
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