傳送GET方法的請求

    /**
     * 向指定URL傳送GET方法的請求
     * @param url  傳送請求的URL         
     * @param param   請求引數，格式：name1=value1&name2=value2   
     * @return String 響應結果
     */
    public static String sendGet(String url, String param) {
        String result = "";
        BufferedReader in = null
 
;
        try {
            String urlNameString = url + "?" + param;
            URL realUrl = new URL(urlNameString);
            // 開啟和URL之間的連線
            HttpURLConnection connection = (HttpURLConnection)realUrl.openConnection();
            // 設定通用的請求屬性
            connection.setRequestProperty("accept"
 
, "*/*");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 建立實際的連線
            connection.connect();
            // 獲取所有響應頭欄位
            Map<String, List<String>> map = connection.getHeaderFields();
            // 遍歷所有的響應頭欄位
 

            for (String key : map.keySet()) {
                System.out.println(key + "--->" + map.get(key));
            }
            // 定義 BufferedReader輸入流來讀取URL的響應
            in = new BufferedReader(new InputStreamReader(
                    connection.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("傳送GET請求出現異常！" + e);
            e.printStackTrace();
        }
        // 使用finally塊來關閉輸入流
        finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return result;
    }

傳送POST方法的請求

/**
     * 向指定 URL 傳送POST方法的請求
     * @param url 傳送請求的 URL
     * @param param 請求引數，格式： name1=value1&name2=value2
     * @return  響應結果
     */
    public static String sendPost(String url, String param) {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            URL realUrl = new URL(url);
            // 開啟和URL之間的連線
            URLConnection conn = realUrl.openConnection();
            // 設定通用的請求屬性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 傳送POST請求必須設定如下兩行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            // 獲取URLConnection物件對應的輸出流
            out = new PrintWriter(conn.getOutputStream());
            // 傳送請求引數
            out.print(param);
            // flush輸出流的緩衝
            out.flush();
            // 定義BufferedReader輸入流來讀取URL的響應
            in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("傳送 POST 請求出現異常！"+e);
            e.printStackTrace();
        }
        //使用finally塊來關閉輸出流、輸入流
        finally{
            try{
                if(out!=null){
                    out.close();
                }
                if(in!=null){
                    in.close();
                }
            }
            catch(IOException ex){
                ex.printStackTrace();
            }
        }
        return result;
    }

傳送引數為json型別的POST請求

/**
     傳送HttpPost請求
     * @param strURL  服務地址
     * @param params  Map型別的引數，再用JSONUtils工具把map轉化成json
     * @return 成功:返回json字串<br/>
     */
    public static String jsonPost(String strURL, Map<String, String> params) {
        try {
            URL url = new URL(strURL);// 建立連線
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setUseCaches(false);
            connection.setInstanceFollowRedirects(true);
            connection.setRequestMethod("POST"); // 設定請求方式
            connection.setRequestProperty("Accept", "application/json"); // 設定接收資料的格式
            connection.setRequestProperty("Content-Type", "application/json"); // 設定傳送資料的格式
            connection.connect();
            OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "UTF-8"); // utf-8編碼
            out.append(JSONUtils.obj2String(params));
            out.flush();
            out.close();
            int code = connection.getResponseCode();
            InputStream is = null;
            if (code == 200) {
                is = connection.getInputStream();
            } else {
                is = connection.getErrorStream();
            }

            // 讀取響應
            int length = (int) connection.getContentLength();// 獲取長度
            if (length != -1) {
                byte[] data = new byte[length];
                byte[] temp = new byte[512];
                int readLen = 0;
                int destPos = 0;
                while ((readLen = is.read(temp)) > 0) {
                    System.arraycopy(temp, 0, data, destPos, readLen);
                    destPos += readLen;
                }
                String result = new String(data, "UTF-8"); // utf-8編碼
                System.out.println(result);
                return result;
            }

        } catch (IOException e) {
            logger.error("Exception occur when send http post request!", e);
            System.out.println(e);
        }
        return "error"; // 自定義錯誤資訊
    }

完整程式碼

HttpRequest.java

/**
 * Created by pc on 2018/6/29.
 */
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class HttpRequest {
    /**
     * 向指定URL傳送GET方法的請求
     * @param url  傳送請求的URL         
     * @param param   請求引數，格式：name1=value1&name2=value2   
     * @return String 響應結果
     */
    public static String sendGet(String url, String param) {
        String result = "";
        BufferedReader in = null;
        try {
            String urlNameString = url + "?" + param;
            URL realUrl = new URL(urlNameString);
            // 開啟和URL之間的連線
            HttpURLConnection connection = (HttpURLConnection)realUrl.openConnection();
            // 設定通用的請求屬性
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 建立實際的連線
            connection.connect();
            // 獲取所有響應頭欄位
            Map<String, List<String>> map = connection.getHeaderFields();
            // 遍歷所有的響應頭欄位
            for (String key : map.keySet()) {
                System.out.println(key + "--->" + map.get(key));
            }
            // 定義 BufferedReader輸入流來讀取URL的響應
            in = new BufferedReader(new InputStreamReader(
                    connection.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("傳送GET請求出現異常！" + e);
            e.printStackTrace();
        }
        // 使用finally塊來關閉輸入流
        finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return result;
    }

    /**
     * 向指定 URL 傳送POST方法的請求
     * @param url 傳送請求的 URL
     * @param param 請求引數，格式： name1=value1&name2=value2
     * @return  響應結果
     */
    public static String sendPost(String url, String param) {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            URL realUrl = new URL(url);
            // 開啟和URL之間的連線
            URLConnection conn = realUrl.openConnection();
            // 設定通用的請求屬性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 傳送POST請求必須設定如下兩行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            // 獲取URLConnection物件對應的輸出流
            out = new PrintWriter(conn.getOutputStream());
            // 傳送請求引數
            out.print(param);
            // flush輸出流的緩衝
            out.flush();
            // 定義BufferedReader輸入流來讀取URL的響應
            in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            System.out.println("傳送 POST 請求出現異常！"+e);
            e.printStackTrace();
        }
        //使用finally塊來關閉輸出流、輸入流
        finally{
            try{
                if(out!=null){
                    out.close();
                }
                if(in!=null){
                    in.close();
                }
            }
            catch(IOException ex){
                ex.printStackTrace();
            }
        }
        return result;
    }

     /**
     傳送HttpPost請求
     * @param strURL  服務地址
     * @param params  傳入Map型別的引數，再用JSONUtils工具把map轉化成json
     * @return 成功:返回json字串<br/>
     */
    public static String jsonPost(String strURL, Map<String, String> params) {
        try {
            URL url = new URL(strURL);// 建立連線
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setUseCaches(false);
            connection.setInstanceFollowRedirects(true);
            connection.setRequestMethod("POST"); // 設定請求方式
            connection.setRequestProperty("Accept", "application/json"); // 設定接收資料的格式
            connection.setRequestProperty("Content-Type", "application/json"); // 設定傳送資料的格式
            connection.connect();
            OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "UTF-8"); // utf-8編碼
            out.append(JSONUtils.obj2String(params));
            out.flush();
            out.close();
            int code = connection.getResponseCode();
            InputStream is = null;
            if (code == 200) {
                is = connection.getInputStream();
            } else {
                is = connection.getErrorStream();
            }

            // 讀取響應
            int length = (int) connection.getContentLength();// 獲取長度
            if (length != -1) {
                byte[] data = new byte[length];
                byte[] temp = new byte[512];
                int readLen = 0;
                int destPos = 0;
                while ((readLen = is.read(temp)) > 0) {
                    System.arraycopy(temp, 0, data, destPos, readLen);
                    destPos += readLen;
                }
                String result = new String(data, "UTF-8"); // utf-8編碼
                System.out.println(result);
                return result;
            }

        } catch (IOException e) {
            System.out.println(e);
        }
        return "error"; // 自定義錯誤資訊
    }
}

JSONUtils.java

package com.chinawayltd.test;

import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;
import org.codehaus.jackson.map.annotate.JsonSerialize.Inclusion;
import org.codehaus.jackson.type.JavaType;

import java.io.IOException;
import java.text.SimpleDateFormat;

/**
 * Created by pc on 2018/6/29.
 */
public class JSONUtils {
    private static ObjectMapper objectMapper = new ObjectMapper();

    static {
        // 物件欄位全部列入
        objectMapper.setSerializationInclusion(Inclusion.NON_DEFAULT);

        // 取消預設轉換timestamps形式
        objectMapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS,false);

        // 忽略空bean轉json的錯誤
        objectMapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS,false);

        // 統一日期格式yyyy-MM-dd HH:mm:ss
        objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));

        // 忽略在json字串中存在,但是在java物件中不存在對應屬性的情況
        objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
    }

    /**
     * Object轉json字串
     * @param obj
     * @param <T>
     * @return
     */
    public static <T> String obj2String(T obj){
        if (obj == null){
            return null;
        }
        try {
            return obj instanceof String ? (String) obj : objectMapper.writeValueAsString(obj);
        } catch (Exception e) {
            System.out.println("Parse object to String error");
            e.printStackTrace();
            return null;
        }
    }

    /**
     * Object轉json字串並格式化美化
     * @param obj
     * @param <T>
     * @return
     */
    public static <T> String obj2StringPretty(T obj){
        if (obj == null){
            return null;
        }
        try {
            return obj instanceof String ? (String) obj : objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
        } catch (Exception e) {
            System.out.println("Parse object to String error");
            e.printStackTrace();
            return null;
        }
    }

    /**
     * string轉object 用於轉為集合物件
     * @param str json字串
     * @param collectionClass 被轉集合class
     * @param elementClasses 被轉集合中物件型別class
     * @param <T>
     * @return
     */
    public static <T> T string2Obj(String str,Class<?> collectionClass,Class<?>... elementClasses){
        JavaType javaType = objectMapper.getTypeFactory().constructParametricType(collectionClass,elementClasses);
        try {
            return objectMapper.readValue(str,javaType);
        } catch (IOException e) {
            System.out.println("Parse String to Object error");
            e.printStackTrace();
            return null;
        }
    }
}