Java 发送http请求

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/galen2016/article/details/80918212

发送GET方法的请求

    /**
     * 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，格式：name1=value1&name2=value2   
     * @return String 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
            HttpURLConnection connection = (HttpURLConnection)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;
    }

发送POST方法的请求

/**
     * 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，格式： name1=value1&name2=value2
     * @return  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;
    }

发送参数为json类型的POST请求

/**
     发送HttpPost请求
     * @param strURL  服务地址
     * @param params  Map类型的参数，再用JSONUtils工具把map转化成json
     * @return 成功:返回json字符串<br/>
     */
    public static String jsonPost(String strURL, Map<String, String> params) {
        try {
            URL url = new URL(strURL);// 创建连接
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setUseCaches(false);
            connection.setInstanceFollowRedirects(true);
            connection.setRequestMethod("POST"); // 设置请求方式
            connection.setRequestProperty("Accept", "application/json"); // 设置接收数据的格式
            connection.setRequestProperty("Content-Type", "application/json"); // 设置发送数据的格式
            connection.connect();
            OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "UTF-8"); // utf-8编码
            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();
            }

            // 读取响应
            int length = (int) connection.getContentLength();// 获取长度
            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编码
                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"; // 自定义错误信息
    }

完整代码

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发送GET方法的请求
     * @param url  发送请求的URL         
     * @param param   请求参数，格式：name1=value1&name2=value2   
     * @return String 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
            HttpURLConnection connection = (HttpURLConnection)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;
    }

    /**
     * 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，格式： name1=value1&name2=value2
     * @return  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;
    }

     /**
     发送HttpPost请求
     * @param strURL  服务地址
     * @param params  传入Map类型的参数，再用JSONUtils工具把map转化成json
     * @return 成功:返回json字符串<br/>
     */
    public static String jsonPost(String strURL, Map<String, String> params) {
        try {
            URL url = new URL(strURL);// 创建连接
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setUseCaches(false);
            connection.setInstanceFollowRedirects(true);
            connection.setRequestMethod("POST"); // 设置请求方式
            connection.setRequestProperty("Accept", "application/json"); // 设置接收数据的格式
            connection.setRequestProperty("Content-Type", "application/json"); // 设置发送数据的格式
            connection.connect();
            OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "UTF-8"); // utf-8编码
            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();
            }

            // 读取响应
            int length = (int) connection.getContentLength();// 获取长度
            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编码
                System.out.println(result);
                return result;
            }

        } catch (IOException e) {
            System.out.println(e);
        }
        return "error"; // 自定义错误信息
    }
}

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 {
        // 对象字段全部列入
        objectMapper.setSerializationInclusion(Inclusion.NON_DEFAULT);

        // 取消默认转换timestamps形式
        objectMapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS,false);

        // 忽略空bean转json的错误
        objectMapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS,false);

        // 统一日期格式yyyy-MM-dd HH:mm:ss
        objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));

        // 忽略在json字符串中存在,但是在java对象中不存在对应属性的情况
        objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
    }

    /**
     * Object转json字符串
     * @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转json字符串并格式化美化
     * @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转object 用于转为集合对象
     * @param str json字符串
     * @param collectionClass 被转集合class
     * @param elementClasses 被转集合中对象类型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;
        }
    }
}