1、HttpClient介绍

	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 HttpComponents 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。HttpClient已经应用在很多的项目中，并支持HTTPS协议。

	HttpClient 不是浏览器，它是一个客户端 HTTP 协议传输类库。HttpClient 被用来发送和接受 HTTP 消息。HttpClient 不会处理 HTTP 消息的内容，不会进行 javascript 解析，不会关心 content type，如果没有明确设置，HttpClient 也不会对请求进行格式化、重定向 url，或者其他任何和 HTTP 消息传输相关的功能。

2、HttpClientUtils

（1）引入依赖

        <httpclient.version>4.5.12</httpclient.version>
                <!-- apache httpclient组件 -->
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>${httpclient.version}</version>
        </dependency>

（2）返回实体

package cn.edu.bjut.entity;

import java.io.Serializable;

/**
 * @author zheng
 */
public class HttpClientResult implements Serializable {
    private static final long serialVersionUID = 1L;

    /**
     * 响应状态码
     */
    private int code;

    /**
     * 响应数据
     */
    private String content;

    public HttpClientResult(int code, String content) {
        this.code = code;
        this.content = content;
    }

    public HttpClientResult(int code) {
        this.code = code;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    @Override
    public String toString() {
        return "HttpClientResult{" +
                "code=" + code +
                ", content='" + content + '\'' +
                '}';
    }
}

（3）工具类

package cn.edu.bjut.utils;

import cn.edu.bjut.entity.HttpClientResult;
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.*;
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;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.*;

/**
 * @author zheng
 */
public class HttpClientUtils {

    /**
     * 编码格式。发送编码格式统一用UTF-8
     */
    private static final String ENCODING = "UTF-8";

    /**
     * 设置连接超时时间，单位毫秒。
     */
    private static final int CONNECT_TIMEOUT = 6000;

    /**
     * 请求获取数据的超时时间(即响应时间)，单位毫秒。
     */
    private static final int SOCKET_TIMEOUT = 6000;

    /**
     * 发送get请求；不带请求头和请求参数
     *
     * @param url 请求地址
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doGet(String url) throws Exception {
        return doGet(url, null, null);
    }

    /**
     * 发送get请求；带请求参数
     *
     * @param url    请求地址
     * @param params 请求参数集合
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doGet(String url, Map<String, String> params) throws Exception {
        return doGet(url, null, params);
    }

    /**
     * 发送get请求；带请求头和请求参数
     *
     * @param url     请求地址
     * @param headers 请求头集合
     * @param params  请求参数集合
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doGet(String url, Map<String, String> headers, Map<String, String> params) throws Exception {
        // 创建httpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        // 创建访问的地址
        URIBuilder uriBuilder = new URIBuilder(url);
        if (params != null) {
            Set<Map.Entry<String, String>> entrySet = params.entrySet();
            for (Map.Entry<String, String> entry : entrySet) {
                uriBuilder.setParameter(entry.getKey(), entry.getValue());
            }
        }

        // 创建http对象
        HttpGet httpGet = new HttpGet(uriBuilder.build());
        /**
         * setConnectTimeout：设置连接超时时间，单位毫秒
         * setConnectionRequestTimeout：设置从connect Manager(连接池)获取Connection
         * setSocketTimeout：请求获取数据的超时时间(即响应时间)，单位毫秒
         */
        RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(CONNECT_TIMEOUT).setSocketTimeout(SOCKET_TIMEOUT).build();
        httpGet.setConfig(requestConfig);

        // 设置请求头
        packageHeader(headers, httpGet);

        // 创建httpResponse对象
        CloseableHttpResponse httpResponse = null;

        try {
            // 执行请求并获得响应结果
            return getHttpClientResult(httpResponse, httpClient, httpGet);
        } finally {
            // 释放资源
            release(httpResponse, httpClient);
        }
    }

    /**
     * 发送post请求；不带请求头和请求参数
     *
     * @param url 请求地址
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doPost(String url) throws Exception {
        return doPost(url, null, null);
    }

    /**
     * 发送post请求；带请求参数
     *
     * @param url    请求地址
     * @param params 参数集合
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doPost(String url, Map<String, String> params) throws Exception {
        return doPost(url, null, params);
    }

    /**
     * 发送post请求；带请求头和请求参数
     *
     * @param url     请求地址
     * @param headers 请求头集合
     * @param params  请求参数集合
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doPost(String url, Map<String, String> headers, Map<String, String> params) throws Exception {
        // 创建httpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        // 创建http对象
        HttpPost httpPost = new HttpPost(url);
        /**
         * setConnectTimeout：设置连接超时时间，单位毫秒
         * setConnectionRequestTimeout：设置从connect Manager(连接池)获取Connection
         * setSocketTimeout：请求获取数据的超时时间(即响应时间)，单位毫秒
         */
        RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(CONNECT_TIMEOUT).setSocketTimeout(SOCKET_TIMEOUT).build();
        httpPost.setConfig(requestConfig);
        // 设置请求头
        packageHeader(headers, httpPost);

        // 封装请求参数
        packageParam(params, httpPost);

        // 创建httpResponse对象
        CloseableHttpResponse httpResponse = null;

        try {
            // 执行请求并获得响应结果
            return getHttpClientResult(httpResponse, httpClient, httpPost);
        } finally {
            // 释放资源
            release(httpResponse, httpClient);
        }
    }

    /**
     * 发送put请求；不带请求参数
     *
     * @param url 请求地址
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doPut(String url) throws Exception {
        return doPut(url);
    }

    /**
     * 发送put请求；带请求参数
     *
     * @param url    请求地址
     * @param params 参数集合
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doPut(String url, Map<String, String> params) throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpPut httpPut = new HttpPut(url);
        RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(CONNECT_TIMEOUT).setSocketTimeout(SOCKET_TIMEOUT).build();
        httpPut.setConfig(requestConfig);

        packageParam(params, httpPut);

        CloseableHttpResponse httpResponse = null;

        try {
            return getHttpClientResult(httpResponse, httpClient, httpPut);
        } finally {
            release(httpResponse, httpClient);
        }
    }

    /**
     * 发送delete请求；不带请求参数
     *
     * @param url 请求地址
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doDelete(String url) throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpDelete httpDelete = new HttpDelete(url);
        RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(CONNECT_TIMEOUT).setSocketTimeout(SOCKET_TIMEOUT).build();
        httpDelete.setConfig(requestConfig);

        CloseableHttpResponse httpResponse = null;
        try {
            return getHttpClientResult(httpResponse, httpClient, httpDelete);
        } finally {
            release(httpResponse, httpClient);
        }
    }

    /**
     * 发送delete请求；带请求参数
     *
     * @param url    请求地址
     * @param params 参数集合
     * @return 返回结果
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult doDelete(String url, Map<String, String> params) throws Exception {
        if (params == null) {
            params = new HashMap<String, String>();
        }

        params.put("_method", "delete");
        return doPost(url, params);
    }

    /**
     * 封装请求头
     *
     * @param params     参数
     * @param httpMethod 请求方式
     */
    public static void packageHeader(Map<String, String> params, HttpRequestBase httpMethod) {
        // 封装请求头
        if (params != null) {
            Set<Map.Entry<String, String>> entrySet = params.entrySet();
            for (Map.Entry<String, String> entry : entrySet) {
                // 设置到请求头到HttpRequestBase对象中
                httpMethod.setHeader(entry.getKey(), entry.getValue());
            }
        }
    }

    /**
     * 封装请求参数
     *
     * @param params     返回结果
     * @param httpMethod 请求方式
     * @throws UnsupportedEncodingException 异常抛出 未处理
     */
    public static void packageParam(Map<String, String> params, HttpEntityEnclosingRequestBase httpMethod)
            throws UnsupportedEncodingException {
        // 封装请求参数
        if (params != null) {
            List<NameValuePair> nvps = new ArrayList<NameValuePair>();
            Set<Map.Entry<String, String>> entrySet = params.entrySet();
            for (Map.Entry<String, String> entry : entrySet) {
                nvps.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
            }

            // 设置到请求的http对象中
            httpMethod.setEntity(new UrlEncodedFormEntity(nvps, ENCODING));
        }
    }

    /**
     * 获得响应结果
     *
     * @param httpResponse 响应
     * @param httpClient   http客户端
     * @param httpMethod   请求方式
     * @return 返回结果集
     * @throws Exception 异常抛出 未处理
     */
    public static HttpClientResult getHttpClientResult(CloseableHttpResponse httpResponse,
                                                       CloseableHttpClient httpClient, HttpRequestBase httpMethod) throws Exception {
        // 执行请求
        httpResponse = httpClient.execute(httpMethod);

        // 获取返回结果
        if (httpResponse != null && httpResponse.getStatusLine() != null) {
            String content = "";
            if (httpResponse.getEntity() != null) {
                content = EntityUtils.toString(httpResponse.getEntity(), ENCODING);
            }
            return new HttpClientResult(httpResponse.getStatusLine().getStatusCode(), content);
        }
        return new HttpClientResult(HttpStatus.SC_INTERNAL_SERVER_ERROR);
    }

    /**
     * 释放资源
     *
     * @param httpResponse 响应
     * @param httpClient   http客户端
     * @throws IOException 异常抛出 未处理
     */
    public static void release(CloseableHttpResponse httpResponse, CloseableHttpClient httpClient) throws IOException {
        // 释放资源
        if (httpResponse != null) {
            httpResponse.close();
        }
        if (httpClient != null) {
            httpClient.close();
        }
    }
}