HttpUtils工具类

作为Java开发程序员，需要我们经常写一些工具类来简化开发过程，我们自己肯定写过或者用过HttpUtils用来发送http请求，但是每次手写太繁琐了，于是就按照标准写了一个Http工具类，现在分享出来。

1.HTTP请求简介

HTTP(Hypertest Transfer Protocol)是用于传输像HTML这样的超文本文件的应用层协议。它被设计用于WEB浏览器端和WEB服务端的交互，但也有其它用途。HTTP遵循经典的client-server模型，客户端发起请求尝试建立连接，然后等待服务端的应答。HTTP是无状态协议，这意味着服务端在两次请求间不会记录任何状态。

2.Http请求四要素

一个HTTP请求报文由四个部分组成：请求行、请求头部、空行、请求数据。

1、请求行

请求行由请求方法字段、URL字段和HTTP协议版本字段3个字段组成，它们用空格分隔。

2、请求头部

HTTP客户程序（例如浏览器），向服务器发送请求的时候必须指明请求类型（一般是GET或者POST)。如有必要，客户程序还可以选择发送其他的请求头。大多数请求头并不是必需的，但Content-Length除外。对于POST请求来说Content-Length必须出现。

3、空行

它的作用是通过一个空行，告诉服务器请求头部到此为止。

4、请求数据

若方法字段是GET，则此项为空，没有数据。若方法字段是POST,则通常来说此处放置的就是要提交的数据。

HttpUtils的代码

package com.zuoan.utils;

import com.alibaba.fastjson.JSON;
import lombok.extern.slf4j.Slf4j;
import org.apache.http.Consts;
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.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.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

public class HttpUtil {

    private static final CloseableHttpClient httpclient = HttpClients.createDefault();
    private static final String userAgent = "Mozilla/5.0 (Windows NT 6.2; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.87 Safari/537.36";

    /**
     * 发送HttpGet请求
     */
    public static String sendGet(String url, String token) {

        String result = null;
        CloseableHttpResponse response = null;
        try {
            URIBuilder uriBuilder = new URIBuilder(url);
            HttpGet httpGet = new HttpGet(url);
            httpGet.setHeader("User-Agent", userAgent);
            httpGet.setHeader("Authorization", "token " + token);
            response = httpclient.execute(httpGet);
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                result = EntityUtils.toString(entity);
            }
        } catch (Exception e) {
            log.error("处理失败 {}" + e);
            e.printStackTrace();
        } finally {
            if (response != null) {
                try {
                    response.close();
                } catch (IOException e) {
                    log.error(e.getMessage());
                }
            }

        }
        return result;
    }

    /**
     * 发送HttpGet请求，参数为map格式
     */
    public static String sendGet(String url, Map<String, String> map) {

        String result = null;
        CloseableHttpResponse response = null;
        try {
            URIBuilder uriBuilder = new URIBuilder(url);
            for (Map.Entry<String, String> entry : map.entrySet()) {
                uriBuilder.setParameter(entry.getKey(), entry.getValue());
            }
            HttpGet httpGet = new HttpGet(uriBuilder.build());
            httpGet.setHeader("User-Agent", userAgent);
            response = httpclient.execute(httpGet);
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                result = EntityUtils.toString(entity);
            }
        } catch (Exception e) {
            log.error("处理失败 {}" + e);
            e.printStackTrace();
        } finally {
            if (response != null) {
                try {
                    response.close();
                } catch (IOException e) {
                    log.error(e.getMessage());
                }
            }

        }
        return result;
    }

    /**
     * 发送HttpPost请求，参数为map
     */
    public static String sendPost(String url, Map<String, String> map) {
        // 设置参数
        List<NameValuePair> formparams = new ArrayList<NameValuePair>();
        for (Map.Entry<String, String> entry : map.entrySet()) {
            formparams.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
        }
        // 编码
        UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(formparams, Consts.UTF_8);
        // 设置content-type
        formEntity.setContentType("application/json");
        // 取得HttpPost对象
        HttpPost httpPost = new HttpPost(url);
        // 防止被当成攻击添加的
        httpPost.setHeader("User-Agent", userAgent);
        // 接收参数设置
        httpPost.setHeader("Accept", "application/json");
        // 参数放入Entity
        httpPost.setEntity(formEntity);
        CloseableHttpResponse response = null;
        String result = null;
        try {
            // 执行post请求
            response = httpclient.execute(httpPost);
            // 得到entity
            HttpEntity entity = response.getEntity();
            // 得到字符串
            result = EntityUtils.toString(entity);
        } catch (IOException e) {
            log.error(e.getMessage());
        } finally {
            if (response != null) {
                try {
                    response.close();
                } catch (IOException e) {
                    log.error(e.getMessage());
                }
            }
        }
        return result;
    }

    /**
     * 发送HttpPost请求，参数为json字符串
     */
    public static String sendPost(String url, String jsonStr) {
        String result = null;
        // 字符串编码
        StringEntity entity = new StringEntity(jsonStr, Consts.UTF_8);
        // 设置content-type
        entity.setContentType("application/json");
        HttpPost httpPost = new HttpPost(url);
        // 防止被当成攻击添加的
        httpPost.setHeader("User-Agent", userAgent);
        // 接收参数设置
        httpPost.setHeader("Accept", "application/json");
        httpPost.setEntity(entity);
        CloseableHttpResponse response = null;
        try {
            response = httpclient.execute(httpPost);
            HttpEntity httpEntity = response.getEntity();
            result = EntityUtils.toString(httpEntity);
        } catch (IOException e) {
            log.error(e.getMessage());
        } finally {
            // 关闭CloseableHttpResponse
            if (response != null) {
                try {
                    response.close();
                } catch (IOException e) {
                    log.error(e.getMessage());
                }
            }
        }
        return result;
    }

    /**
     * 发送不带参数的HttpPost请求
     */
    public static String sendPost(String url) {
        String result = null;
        // 得到一个HttpPost对象
        HttpPost httpPost = new HttpPost(url);
        // 防止被当成攻击添加的
        httpPost.setHeader("User-Agent", userAgent);
        CloseableHttpResponse response = null;
        try {
            // 执行HttpPost请求，并得到一个CloseableHttpResponse
            response = httpclient.execute(httpPost);
            // 从CloseableHttpResponse中拿到HttpEntity
            HttpEntity entity = response.getEntity();
            // 将HttpEntity转换为字符串
            result = EntityUtils.toString(entity);
        } catch (IOException e) {
            log.error(e.getMessage());
        } finally {
            // 关闭CloseableHttpResponse
            if (response != null) {
                try {
                    response.close();
                } catch (IOException e) {
                    log.error(e.getMessage());
                }
            }
        }
        return result;
    }
}
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