Spring框架学习[Spring HTTP调用器实现远程调用] - JAVA

ld not access HTTP invoker remote service at [" + getServiceUrl() + "]", ex); } } }

通过上面对HttpInvokerClientInterceptor拦截器的源码分析，我们可以看出，拦截器将客户端对远程调用的HTTP请求封装成了MethodInvocation对象，拦截器的在调用远程调用的代理对象时，又将方法调用封装成了RemoteInvocation远程调用，RemoteInvocation数据对象中封装了调用的具体信息，如方法名、方法参数以及参数类型等。

真正执行远程调用的是HTTP调用请求执行器SimpleHttpInvokerRequestExecutor，下面我们继续分析SimpleHttpInvokerRequestExecutor远程调用的具体过程。

5.SimpleHttpInvokerRequestExecutor远程调用：

SimpleHttpInvokerRequestExecutor封装了基于HTTP协议的远程调用过程，具体源码如下：

[java] view plaincopyprint

public class SimpleHttpInvokerRequestExecutor extends AbstractHttpInvokerRequestExecutor { //HTTP调用请求执行器真正进行远程调用的方法，该方法有其父类//AbstractHttpInvokerRequestExecutor的executeRequest方法调用
protected RemoteInvocationResult doExecuteRequest( HttpInvokerClientConfiguration config, ByteArrayOutputStream baos)
throws IOException, ClassNotFoundException { //打开一个标准的J2SE HttpURLConnection
HttpURLConnection con = openConnection(config); //准备连接
prepareConnection(con, baos.size()); //远程调用被封装成了RemoteInvocation对象，它通过序列化被写到对应的//HttpURLConnection中
writeRequestBody(config, con, baos); //获取远程调用的结果，校验返回的结果
validateResponse(config, con); InputStream responseBody = readResponseBody(config, con);
//将远程调用结果转换成RemoteInvocationResult返回 return readRemoteInvocationResult(responseBody, config.getCodebaseUrl());
} //打开一个HttpURLConnection
protected HttpURLConnection openConnection(HttpInvokerClientConfiguration config) throws IOException { //getServiceUrl()方法获取配置的远程调用URL，打开一个URL连接
URLConnection con = new URL(config.getServiceUrl()).openConnection(); if (!(con instanceof HttpURLConnection)) {
throw new IOException("Service URL [" + config.getServiceUrl() + "] is not an HTTP URL"); }
return (HttpURLConnection) con; }
//准备HTTP请求连接 protected void prepareConnection(HttpURLConnection con, int contentLength) throws IOException {
con.setDoOutput(true); //HTTP调用器只支持POST请求方法
con.setRequestMethod(HTTP_METHOD_POST); //设置HTTP请求头内容类型，设置为：application/x-java-serialized-object
con.setRequestProperty(HTTP_HEADER_CONTENT_TYPE, getContentType()); //设置HTTP请求头内容长度
con.setRequestProperty(HTTP_HEADER_CONTENT_LENGTH, Integer.toString(contentLength)); LocaleContext locale = LocaleContextHolder.getLocaleContext();
//设置HTTP请求的Locale if (locale != null) {
con.setRequestProperty(HTTP_HEADER_ACCEPT_LANGUAGE, StringUtils.toLanguageTag(locale.getLocale())); }
//设置HTTP请求压缩方式 if (isAcceptGzipEncoding()) {
con.setRequestProperty(HTTP_HEADER_ACCEPT_ENCODING, ENCODING_GZIP); }
} //把序列化对象输出到HTTP请求体中
protected void writeRequestBody( HttpInvokerClientConfiguration config, HttpURLConnection con, ByteArrayOutputStream baos)
throws IOException { baos.writeTo(con.getOutputStream());
} //校验远程调用的HTTP响应
protected void validateResponse(HttpInvokerClientConfiguration config, HttpURLConnection con) throws IOException {
//如果HTTP响应状态码大于等于300，则证明调用发生错误 if (con.getResponseCode() >= 300) {
throw new IOException( "Did not receive successful HTTP response: status code = " + con.getResponseCode() +
", status message = [" + con.getResponseMessage() + "]"); }
} //提取远程调用结果的HTTP响应信息
protected InputStream readResponseBody(HttpInvokerClientConfiguration config, HttpURLConnection con) throws IOException {
//如果响应信息是

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