Java訪問http/https方法

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1、問題描述

　　有時候需要在Java后台去訪問其他系統api，這些接口可能是http或https的。在網上搜索了下，還不少人提問，但是有些過於繁瑣於是自己整理了一篇博客。

2、代碼樣例

　　1、引入pom，版本一定要高一點的不然會報錯。

     <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.5.3</version>
    </dependency>

　　2、代碼例子

package com.mao2080.util;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.util.HashMap;
import java.util.Map;

/**
 * HttpClient工具類
 */
public class HttpClientUtil {

    /**請求編碼*/
    private static final String DEFAULT_CHARSET = "UTF-8";

    /**
     * 執行HTTP POST請求
     * @param url url
     * @param param 參數
     * @return
     */
    public static String httpPostWithJSON(String url, Map<String, ?> param) {
        CloseableHttpClient client = null;
        try {
            if(url == null || url.trim().length() == 0){
                throw new Exception("URL is null");
            }
            HttpPost httpPost = new HttpPost(url);
            client = HttpClients.createDefault();
            if(param != null){
                StringEntity entity = new StringEntity(JSONUtils.toJSONString(param), DEFAULT_CHARSET);//解決中文亂碼問題
                entity.setContentEncoding(DEFAULT_CHARSET);
                entity.setContentType("application/json");
                httpPost.setEntity(entity);
            }
            HttpResponse resp = client.execute(httpPost);
            if(resp.getStatusLine().getStatusCode() == 200) {
                return EntityUtils.toString(resp.getEntity(), DEFAULT_CHARSET);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            close(client);
        }
        return null;
    }

    /**
     * 執行HTTP GET請求
     * @param url url
     * @param param 參數
     * @return
     */
    public static String httpGetWithJSON(String url, Map<String, ?> param) {
        CloseableHttpClient client = null;
        try {
            if(url == null || url.trim().length() == 0){
                throw new Exception("URL is null");
            }
            client = HttpClients.createDefault();
            if(param != null){
                StringBuffer sb = new StringBuffer("?");
                for (String key : param.keySet()){
                    sb.append(key).append("=").append(param.get(key)).append("&");
                }
                url = url.concat(sb.toString());
                url = url.substring(0, url.length()-1);
            }
            HttpGet httpGet = new HttpGet(url);
            HttpResponse resp = client.execute(httpGet);
            if(resp.getStatusLine().getStatusCode() == 200) {
                return EntityUtils.toString(resp.getEntity(), DEFAULT_CHARSET);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            close(client);
        }
        return null;
    }

    /**
     * 關閉HTTP請求
     * @param client
     */
    private static void close(CloseableHttpClient client){
        if(client == null){
            return;
        }
        try {
            client.close();
        } catch (Exception e) {
        }
    }

    public static void main(String[] args) throws Exception {
        Map param = new HashMap();
        param.put("userName", "admin");
        param.put("password", "mao2080");
        String result = httpGetWithJSON("https://www.baidu.com/", param);
        System.out.println("result:"+result);
    }


}

　　3、運行結果

　　

3、參考網站

　　https://www.cnblogs.com/Vdiao/p/5339487.html