HttpClient工具类（使用连接池）
HttpClient工具类（使用连接池）
HttpClient简介
\(~~~~~\)HTTP 协议可能是现在 Internet 上使用得最多、最重要的协议了，越来越多的 Java 应用程序需要直接通过 HTTP 协议来访问网络资源。虽然在 JDK 的 java net包中已经提供了访问 HTTP 协议的基本功能，但是对于大部分应用程序来说，JDK 库本身提供的功能还不够丰富和灵活。HttpClient 是 Apache Jakarta Common 下的子项目，用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包，并且它支持 HTTP 协议最新的版本和建议。
\(~~~~~\)HTTP和浏览器有点像，但却不是浏览器。很多人觉得既然HttpClient是一个HTTP客户端编程工具，很多人把他当做浏览器来理解，但是其实HttpClient不是浏览器，它是一个HTTP通信库，因此它只提供一个通用浏览器应用程序所期望的功能子集，最根本的区别是HttpClient中没有用户界面，浏览器需要一个渲染引擎来显示页面，并解释用户输入，例如鼠标点击显示页面上的某处，有一个布局引擎，计算如何显示HTML页面，包括级联样式表和图像。javascript解释器运行嵌入HTML页面或从HTML页面引用的javascript代码。来自用户界面的事件被传递到javascript解释器进行处理。除此之外，还有用于插件的接口，可以处理Applet，嵌入式媒体对象（如pdf文件，Quicktime电影和Flash动画）或ActiveX控件（可以执行任何操作）。HttpClient只能以编程的方式通过其API用于传输和接受HTTP消息
HttpClient主要功能
- 实现了所有 HTTP 的方法（GET、POST、PUT、HEAD、DELETE、HEAD、OPTIONS 等）
- 支持 HTTPS 协议
- 支持代理服务器（Nginx等）等
- 支持自动（跳转）转向
简单使用
引入相关依赖
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.5</version>
</dependency>
这里提醒一点：springboot中也已经整合有HttpClient依赖，也可以另外引入依赖
单独发送Get请求
/**
* 向指定URL发送GET方法的请求
*
* @param url
* 发送请求的URL
* @param param
* 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
* @return URL 所代表远程资源的响应结果
*/
public static String sendGet(String url, String param) {
String result = "";
BufferedReader in = null;
try {
String urlNameString = url + "?" + param;
URL realUrl = new URL(urlNameString);
// 打开和URL之间的连接
URLConnection connection = realUrl.openConnection();
// 设置通用的请求属性
connection.setRequestProperty("accept", "*/*");
connection.setRequestProperty("connection", "Keep-Alive");
connection.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
// 建立实际的连接
connection.connect();
// 获取所有响应头字段
Map<String, List<String>> map = connection.getHeaderFields();
// 遍历所有的响应头字段
for (String key : map.keySet()) {
System.out.println(key + "--->" + map.get(key));
}
// 定义 BufferedReader输入流来读取URL的响应
in = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
} catch (Exception e) {
System.out.println("发送GET请求出现异常！" + e);
e.printStackTrace();
}
// 使用finally块来关闭输入流
finally {
try {
if (in != null) {
in.close();
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
return result;
}
单独发送Post请求
post请求有两种方式传参，一种是普通参数，一种是对象参数
/**
* 向指定 URL 发送POST方法的请求
*
* @param url
* 发送请求的 URL
* @param param
* 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
* @return 所代表远程资源的响应结果
*/
public static String sendPost(String url, String param) {
PrintWriter out = null;
BufferedReader in = null;
String result = "";
try {
URL realUrl = new URL(url);
// 打开和URL之间的连接
URLConnection conn = realUrl.openConnection();
// 设置通用的请求属性
conn.setRequestProperty("accept", "*/*");
conn.setRequestProperty("connection", "Keep-Alive");
conn.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
// 发送POST请求必须设置如下两行
conn.setDoOutput(true);
conn.setDoInput(true);
// 获取URLConnection对象对应的输出流
out = new PrintWriter(conn.getOutputStream());
// 发送请求参数
out.print(param);
// flush输出流的缓冲
out.flush();
// 定义BufferedReader输入流来读取URL的响应
in = new BufferedReader(
new InputStreamReader(conn.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
} catch (Exception e) {
System.out.println("发送 POST 请求出现异常！"+e);
e.printStackTrace();
}
//使用finally块来关闭输出流、输入流
finally{
try{
if(out!=null){
out.close();
}
if(in!=null){
in.close();
}
}
catch(IOException ex){
ex.printStackTrace();
}
}
return result;
}
使用HttpClient连接池，优化连接
- 这里整合在springboot :2.2.6.RELEASE 版本
package com.vx.music.http;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpRequestBase;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import java.io.*;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
public class HttpClientApiUtils {
private static PoolingHttpClientConnectionManager cm;
private static String EMPTY_STR = "";
private static String UTF_8 = "UTF-8";
private static void init() {
if (cm == null) {
cm = new PoolingHttpClientConnectionManager();
// 整个连接池最大连接数
cm.setMaxTotal(100);
// 每路由最大连接数，默认值是2
cm.setDefaultMaxPerRoute(5);
}
}
/**
* 通过连接池获取HttpClient
*
* @return
*/
private static CloseableHttpClient getHttpClient() {
init();
return HttpClients.custom().setConnectionManager(cm).build();
}
/**
* @param url
* @return
*/
public static String httpGetRequest(String url) {
HttpGet httpGet = new HttpGet(url);
return getResult(httpGet);
}
public static String httpGetRequest(String url, Map<String, Object> params) throws URISyntaxException {
URIBuilder ub = new URIBuilder(url);
ArrayList<NameValuePair> pairs = covertParams2NVPS(params);
ub.setParameters(pairs);
HttpGet httpGet = new HttpGet(ub.build());
return getResult(httpGet);
}
public static String httpGetRequest(String url, Map<String, Object> headers, Map<String, Object> params)
throws URISyntaxException {
URIBuilder ub = new URIBuilder();
ub.setPath(url);
ArrayList<NameValuePair> pairs = covertParams2NVPS(params);
ub.setParameters(pairs);
HttpGet httpGet = new HttpGet(ub.build());
for (Map.Entry<String, Object> param : headers.entrySet()) {
httpGet.addHeader(param.getKey(), String.valueOf(param.getValue()));
}
return getResult(httpGet);
}
public static String httpPostRequest(String url) {
HttpPost httpPost = new HttpPost(url);
return getResult(httpPost);
}
public static String httpPostRequest(String url,String json) {
HttpPost httpPost = new HttpPost(url);
StringEntity entity = new StringEntity(json,"utf-8");//解决中文乱码问题
entity.setContentEncoding("UTF-8");
entity.setContentType("application/json");
httpPost.setEntity(entity);
return getResult(httpPost);
}
public static String httpPostRequest(String url, Map<String, Object> params) throws UnsupportedEncodingException {
HttpPost httpPost = new HttpPost(url);
ArrayList<NameValuePair> pairs = covertParams2NVPS(params);
httpPost.setEntity(new UrlEncodedFormEntity(pairs, UTF_8));
return getResult(httpPost);
}
public static String httpPostRequest(String url, Map<String, Object> headers, Map<String, Object> params)
throws UnsupportedEncodingException {
HttpPost httpPost = new HttpPost(url);
for (Map.Entry<String, Object> param : headers.entrySet()) {
httpPost.addHeader(param.getKey(), String.valueOf(param.getValue()));
}
ArrayList<NameValuePair> pairs = covertParams2NVPS(params);
httpPost.setEntity(new UrlEncodedFormEntity(pairs, UTF_8));
return getResult(httpPost);
}
private static ArrayList<NameValuePair> covertParams2NVPS(Map<String, Object> params) {
ArrayList<NameValuePair> pairs = new ArrayList<NameValuePair>();
for (Map.Entry<String, Object> param : params.entrySet()) {
pairs.add(new BasicNameValuePair(param.getKey(), String.valueOf(param.getValue())));
}
return pairs;
}
/**
* 处理Http请求
*/
private static String getResult(HttpRequestBase request) {
// CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpClient httpClient = getHttpClient();
try {
CloseableHttpResponse response = httpClient.execute(request);
// response.getStatusLine().getStatusCode();
HttpEntity entity = response.getEntity();
if (entity != null) {
// long len = entity.getContentLength();// -1 表示长度未知
String result = EntityUtils.toString(entity);
response.close();
// httpClient.close();
return result;
}
} catch (IOException e) {
e.printStackTrace();
}
return EMPTY_STR;
}
}
HttpClient4.X发送Get请求的参数拼接
使用httpClient发送get请求时，请求参数可以以？key=val&key1=val1的拼接到url后面。
但是请求参数较多时，这种方法比较麻烦，也不太优雅；研究了一下发现HttpClient4.X本身
是支持处理参数的。
1. 使用 URIBuilder来构建请求URI
import com.google.common.collect.Lists;
import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.HttpStatus;
import org.apache.http.NameValuePair;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
private HttpGet buildHttpGet(String url, Map<String, String> para)
throws URISyntaxException {
URIBuilder builder = new URIBuilder(url);
Set<String> set = para.keySet();
for(String key: set){
builder.setParameter(key, para.get(key));
}
HttpGet request = new HttpGet(builder.build());
RequestConfig requestConfig = RequestConfig.custom()
.setSocketTimeout(6000)
.setConnectTimeout(6000)
.setConnectionRequestTimeout(6000).build();
request.setConfig(requestConfig);
System.out.println(request.getURI().toString());
return request;
}
2. 使用 NameValuePair 来拼接URI
List<NameValuePair> params = Lists.newArrayList();
params.add(new BasicNameValuePair("cityEname", "henan"));
String str = "";
//转换为键值对
str = EntityUtils.toString(new UrlEncodedFormEntity(params, Consts.UTF_8));
System.out.println(str);
HttpGet httpGet = new HttpGet(url + "?" + str);
3. 根据 HttpGet反向获取键值对列表
HttpGet request = new HttpGet("http://example.com/?var=1&var=2");
URIBuilder newBuilder = new URIBuilder(request.getURI());
//获取键值对列表
List<NameValuePair> params = newBuilder.getQueryParams();
//转换为键值对字符串
String str = EntityUtils.toString(new UrlEncodedFormEntity(params, Consts.UTF_8));
其它
其它更多其它详细使用：
https://github.com/Arronlong/httpclientutil
