HttpClient POST 的 UTF-8 编码问题

Apache HttpClient ( http://jakarta.apache.org/commons/httpclient/ ) 是一个纯 Java 的HTTP 协议的客户端编程工具包, 对 HTTP 协议的支持相当全面, 更多细节也可以参考IBM 网站上的这篇文章 HttpClient入门 ( http://www-128.ibm.com/developerworks/cn/opensource/os-httpclient/ ).

问题分析不过在实际使用中, 还是发现按照最基本的方式调用 HttpClient 时, 并不支持 UTF-8 编码, 在网络上找过一些文章, 也不得要领, 于是查看了 commons-httpclient-3.0.1 的一些代码, 首先在 PostMethod 中找到了 generateRequestEntity() 方法:

/** * Generates a request entity from the post parameters, if present. Calls * {@link EntityEnclosingMethod#generateRequestBody()} if parameters have not been set. * * @since 3.0 */ protected RequestEntity generateRequestEntity() { if (!this.params.isEmpty()) { // Use a ByteArrayRequestEntity instead of a StringRequestEntity. // This is to avoid potential encoding issues. Form url encoded strings // are ASCII by definition but the content type may not be. Treating the content // as bytes allows us to keep the current charset without worrying about how // this charset will effect the encoding of the form url encoded string. String content = EncodingUtil.formUrlEncode(getParameters(), getRequestCharSet()); ByteArrayRequestEntity entity = new ByteArrayRequestEntity( EncodingUtil.getAsciiBytes(content), FORM_URL_ENCODED_CONTENT_TYPE ); return entity; } else { return super.generateRequestEntity(); } }

原来使用 NameValuePair 加入的 HTTP 请求的参数最终都会转化为 RequestEntity 提交到 HTTP 服务器, 接着在 PostMethod 的父类 EntityEnclosingMethod 中找到了如下的代码:

/** * Returns the request's charset. The charset is parsed from the request entity's * content type, unless the content type header has been set manually. * * @see RequestEntity#getContentType() * * @since 3.0 */ public String getRequestCharSet() { if (getRequestHeader("Content-Type") == null) { // check the content type from request entity // We can't call getRequestEntity() since it will probably call // this method. if (this.requestEntity != null) { return getContentCharSet( new Header("Content-Type", requestEntity.getContentType())); } else { return super.getRequestCharSet(); } } else { return super.getRequestCharSet(); } }

解决方案从上面两段代码可以看出是 HttpClient 是如何依据 "Content-Type" 获得请求的编码(字符集), 而这个编码又是如何应用到提交内容的编码过程中去的. 按照这个原来, 其实我们只需要重载 getRequestCharSet() 方法, 返回我们需要的编码(字符集)名称, 就可以解决 UTF-8 或者其它非默认编码提交 POST 请求时的乱码问题了.

测试首先在 Tomcat 的 ROOT WebApp 下部署一个页面 test.jsp, 作为测试页面, 主要代码片段如下:

<%@ page contentType="text/html;charset=UTF-8"%> <%@ page session="false" %> <% request.setCharacterEncoding("UTF-8"); String val = request.getParameter("TEXT"); System.out.println(">>>> The result is " + val); %>

接着写一个测试类, 主要代码如下:

public static void main(String[] args) throws Exception, IOException { String url = "http://localhost:8080/test.jsp"; PostMethod postMethod = new UTF8PostMethod(url); //填入各个表单域的值 NameValuePair[] data = { new NameValuePair("TEXT", "中文"), }; //将表单的值放入postMethod中 postMethod.setRequestBody(data); //执行postMethod HttpClient httpClient = new HttpClient(); httpClient.executeMethod(postMethod); } //Inner class for UTF-8 support public static class UTF8PostMethod extends PostMethod{ public UTF8PostMethod(String url){ super(url); } @Override public String getRequestCharSet() { //return super.getRequestCharSet(); return "UTF-8"; } }

运行这个测试程序, 在 Tomcat 的后台输出中可以正确打印出 ">>>> The result is 中文" .