Httpclient与RestTemplate的比较（比httpClient更优雅的Restful URL访问）

一、HttpClient

（一）HttpClient 客户端

1、HttpClient 是 apache 的开源，需要引入两个包：httpclient-4.2.4.jar 和 httpcore-4.2.2.jar。

/**
* HttpClien 的客户端访问
*/
private void httpClientVisit() {

String clientResponse = "";
try {

HttpClient client = new DefaultHttpClient();
HttpPost request = new HttpPost(mUrl);

//不是表单数据提交，这边使用 StringEntity 即可
//UrlEncodedFormEntity等都是 HttpEntity 接口的实现类
StringEntity entity = new StringEntity(mRequestXml, "UTF-8");//编码
entity.setContentType("text/xml");
request.setEntity(entity);
// 发送请求
HttpResponse response = client.execute(request);

org.apache.http.HttpEntity httpEntity = response.getEntity();

if (httpEntity != null) {
// EntityUtils.toString 如果不指定编码，EntityUtils默认会使用ISO_8859_1进行编码
clientResponse = EntityUtils.toString(httpEntity, "UTF-8");// 记得设置编码或者如下
// clientResponse = new String(EntityUtils.toString(httpEntity).getBytes("ISO_8859_1"), "UTF-8");
}

if (clientResponse == null || "".equals(clientResponse)) {
System.err.println("clientResponse is null or empty.");

}

System.out.println(clientResponse);

} catch (Exception e) {
e.printStackTrace();
}

}

（二）HttpClient 详解

1、Post方式访问

/**
* post方式提交表单（模拟用户登录请求）
*/
public void postForm() {

String url = "http://localhost:8080/Java_WS_Server/rest/surpolicy/sendXml";

// 创建默认的httpClient实例.
HttpClient client = new DefaultHttpClient();
// 创建httppost
HttpPost httppost = new HttpPost(url);
// 创建参数队列
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
formparams.add(new BasicNameValuePair("username", "admin"));
formparams.add(new BasicNameValuePair("password", "123456"));
UrlEncodedFormEntity uefEntity;
try {
uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8"); //编码
httppost.setEntity(uefEntity);
System.out.println("executing request " + httppost.getURI());
HttpResponse response = client.execute(httppost);
Header[] headers = response.getAllHeaders();
for(int i=0; i<headers.length; i++){
System.out.println(headers[i].getName());
}

try {
HttpEntity entity = response.getEntity();
if (entity != null) {
System.out.println("--------------------------------------");
System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));  //编码
System.out.println("--------------------------------------");
}
} finally {

}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e1) {
e1.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {

}
}

　　2、Get方式访问

/**
* 发送 get请求
*/
public void get() {
try {
HttpClient client = new DefaultHttpClient();
// 创建httpget.
HttpGet httpget = new HttpGet("http://www.baidu.com/");
System.out.println("executing request " + httpget.getURI());
// 执行get请求.
HttpResponse response = client.execute(httpget);
try {
// 获取响应实体
HttpEntity entity = response.getEntity();
System.out.println("--------------------------------------");
// 打印响应状态
System.out.println(response.getStatusLine());
if (entity != null) {
// 打印响应内容长度
System.out.println("Response content length: " + entity.getContentLength());
// 打印响应内容
System.out.println("Response content: " + EntityUtils.toString(entity));
}
System.out.println("------------------------------------");
} finally {
}
} catch (ClientProtocolException e) {
e.printStackTrace();
}  catch (IOException e) {
e.printStackTrace();
} finally {}
}

　　

3、乱码问题：

1）利用：UrlEncodedFormEntity等 entity 容器，实现发送内容的编码：

UrlEncodedFormEntity uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8"); //编码

StringEntity entity = new StringEntity(mRequestXml, "UTF-8");//编码

2、EntityUtils.toString()方法的转码，实现返回内容的编码：

EntityUtils.toString 如果不指定编码，EntityUtils默认会使用ISO_8859_1进行编码

clientResponse = EntityUtils.toString(httpEntity, "UTF-8");// 记得设置编码或者如下

clientResponse = new String(EntityUtils.toString(httpEntity).getBytes("ISO_8859_1"), "UTF-8");

二、RestTemplate

（一）RestTemplate 客户端

1、RestTemplate 是Spring的封装，需要spring的包 spring-web-3.0.7.RELEASE.jar

2、客户端代码：

/**
* RestTemplate 客户端访问
*/
private void RestTemplateVisit() {
String returnXml = ""; // 核心返回结果报文字符串

try {

//复杂构造函数的使用
SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
requestFactory.setConnectTimeout(1000);// 设置超时
requestFactory.setReadTimeout(1000);

//利用复杂构造器可以实现超时设置，内部实际实现为 HttpClient
RestTemplate restTemplate = new RestTemplate(requestFactory);

//设置HTTP请求头信息，实现编码等
HttpHeaders requestHeaders = new HttpHeaders();
// requestHeaders.set("Accept", "text/");
requestHeaders.set("Accept-Charset", "utf-8");
requestHeaders.set("Content-type", "text/xml; charset=utf-8");// 设置编码

//利用容器实现数据封装，发送
HttpEntity<String> entity = new HttpEntity<String>(mRequestXml, requestHeaders);
returnXml = restTemplate.postForObject(mUrl, entity, String.class);

// 转码原因：RestTemplate默认是使用org.springframework.http.converter.StringHttpMessageConverter来解析
// StringHttpMessageConverter 默认用的 ISO-8859-1来编码的
returnXml = new String(returnXml.getBytes("ISO-8859-1"), "utf-8");

} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}

System.out.println("restTemplate客户端访问返回： \n" + returnXml);
}

　　具体的参考这个博客：
http://blog.csdn.net/u012228718/article/details/42028951