JsonRpc源码--处理http请求源码刨析

从jsonRpc接入http请求直至开始业务逻辑处理总体层级如下：

JsonServiceExporter->handleRequest-> handle -> handleRequest0 ->handleRequest -> handleJsonNodeRequest -> handleObject -> methodInvoke

google的jsonrpc4j通过实现springframework中的httpRequestHandler来对请求进行处理；源码如下：

package com.googlecode.jsonrpc4j.spring;import com.googlecode.jsonrpc4j.JsonRpcServer;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.HttpRequestHandler;class JsonServiceExporter extends AbstractJsonServiceExporter implements HttpRequestHandler {private JsonRpcServer jsonRpcServer;JsonServiceExporter() {}protected void exportService() {this.jsonRpcServer = this.getJsonRpcServer();}public void handleRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.jsonRpcServer.handle(request, response);response.getOutputStream().flush();}
}

进入handle可以看到在此层会对捕获http请求中出现的所有异常，并进行异常处理，回显jsonrpc中自定义的错误代码以及结构；源码如下：


/*** Handles a servlet request.** @param request  the {@link HttpServletRequest}* @param response the {@link HttpServletResponse}* @throws IOException on error*/
public void handle(HttpServletRequest request, HttpServletResponse response) throws IOException {logger.debug("Handling HttpServletRequest {}", request);response.setContentType(contentType);OutputStream output = response.getOutputStream();InputStream input = getRequestStream(request);int result = ErrorResolver.JsonError.PARSE_ERROR.code;int contentLength = 0;ByteArrayOutputStream byteOutput = new ByteArrayOutputStream();try {String acceptEncoding = request.getHeader(ACCEPT_ENCODING);result = handleRequest0(input, output, acceptEncoding, response, byteOutput);contentLength = byteOutput.size();} catch (Throwable t) {if (StreamEndedException.class.isInstance(t)) {logger.debug("Bad request: empty contents!");} else {logger.error(t.getMessage(), t);}}int httpStatusCode = httpStatusCodeProvider == null ? DefaultHttpStatusCodeProvider.INSTANCE.getHttpStatusCode(result): httpStatusCodeProvider.getHttpStatusCode(result);response.setStatus(httpStatusCode);response.setContentLength(contentLength);byteOutput.writeTo(output);output.flush();
}

进入handleRequest0 ->handleRequest -> handleJsonNodeRequest,这一步从输入流中读取对应的请求并归属为jsonrpc请求、处理对应请求，并返回结果代码；源码如下：

/*** Handles a single request from the given {@link InputStream},* that is to say that a single {@link JsonNode} is read from* the stream and treated as a JSON-RPC request.  All responses* are written to the given {@link OutputStream}.** @param input  the {@link InputStream}* @param output the {@link OutputStream}* @return the error code, or {@code 0} if none* @throws IOException on error*/
public int handleRequest(final InputStream input, final OutputStream output) throws IOException {final ReadContext readContext = ReadContext.getReadContext(input, mapper);try {readContext.assertReadable();final JsonNode jsonNode = readContext.nextValue();for (JsonRpcInterceptor interceptor : interceptorList) {interceptor.preHandleJson(jsonNode);}JsonResponse jsonResponse = handleJsonNodeRequest(jsonNode);writeAndFlushValue(output, jsonResponse.getResponse());if (jsonResponse.getExceptionToRethrow() != null) {throw jsonResponse.getExceptionToRethrow();}return jsonResponse.getCode();} catch (JsonParseException | JsonMappingException e) {JsonResponse responseError = createResponseError(VERSION, NULL, JsonError.PARSE_ERROR);writeAndFlushValue(output, responseError.getResponse());return responseError.getCode();}
}

进入handleJsonNodeRequest,这里会对请求体中的json对象进行判别并进行对应处理；源码如下：

/*** Handles the given {@link JsonNode} and creates {@link JsonResponse}** @param node the {@link JsonNode}* @return the {@link JsonResponse} instance*/
protected JsonResponse handleJsonNodeRequest(final JsonNode node)throws JsonParseException, JsonMappingException {if (node.isArray()) {return handleArray((ArrayNode) node);}if (node.isObject()) {return handleObject((ObjectNode) node);}return createResponseError(VERSION, NULL, JsonError.INVALID_REQUEST);
}
REQUEST);}

这里以handleObject为例，进来后其实就是对json的结构进行验证并调用对应方法；部分解析我会写道下面源码里边；

/*** Handles the given {@link ObjectNode} and creates {@link JsonResponse}** @param node   the {@link JsonNode}* @return the {@link JsonResponse} instance*/private JsonResponse handleObject(final ObjectNode node)throws JsonParseException, JsonMappingException {logger.debug("Request: {}", node);// 验证请求中是否存在"jsonRpc" 以及 "method"if (!isValidRequest(node)) {return createResponseError(VERSION, NULL, JsonError.INVALID_REQUEST);}// 获取对应请求idObject id = parseId(node.get(ID));// 验证参数是否为空String jsonRpc = hasNonNullData(node, JSONRPC) ? node.get(JSONRPC).asText() : VERSION;if (!hasNonNullData(node, METHOD)) {return createResponseError(jsonRpc, id, JsonError.METHOD_NOT_FOUND);}// 获取方法路径信息final String fullMethodName = node.get(METHOD).asText();final String partialMethodName = getMethodName(fullMethodName);final String serviceName = getServiceName(fullMethodName);Set<Method> methods = findCandidateMethods(getHandlerInterfaces(serviceName), partialMethodName);if (methods.isEmpty()) {return createResponseError(jsonRpc, id, JsonError.METHOD_NOT_FOUND);}// 验证方法参数是否齐全AMethodWithItsArgs methodArgs = findBestMethodByParamsNode(methods, node.get(PARAMS));if (methodArgs == null) {return createResponseError(jsonRpc, id, JsonError.METHOD_PARAMS_INVALID);}try (InvokeListenerHandler handler = new InvokeListenerHandler(methodArgs, invocationListener)) {try {// 若设置预处理拦截器则会在此处拦截请求if (this.requestInterceptor != null) {this.requestInterceptor.interceptRequest(node);}// serviceName 其实就是我们通过@JsonRpcService设置的层级，在程序启动时会自动加载到内存当中Object target = getHandler(serviceName);// interceptors preHandlefor (JsonRpcInterceptor interceptor : interceptorList) {interceptor.preHandle(target, methodArgs.method, methodArgs.arguments);}// invocation 做内部方法调用执行业务逻辑JsonNode result = invoke(target, methodArgs.method, methodArgs.arguments);handler.result = result;// interceptors postHandle 若设置post拦截器则会在此处拦截请求for (JsonRpcInterceptor interceptor : interceptorList) {interceptor.postHandle(target, methodArgs.method, methodArgs.arguments, result);}// 验证id不为空if (!isNotificationRequest(id)) {return createResponseSuccess(jsonRpc, id, handler.result);}return new JsonResponse(null, JsonError.OK.code);} catch (JsonParseException | JsonMappingException e) {throw e; // rethrow this, it will be handled as PARSE_ERROR later} catch (Throwable e) {handler.error = e;return handleError(id, jsonRpc, methodArgs, e);}}}

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