1 HttpURLConnection

HttpURLConnection是Jdk自带的请求工具,不用依赖第三方jar包,适用简单的场景使用.

使用方式是, 通过调用URL.openConnection方法,得到一个URLConnection对象,并强转为HttpURLConnection对象.

java.net.URL部分源码:

    public URLConnection openConnection() throws java.io.IOException {
        return handler.openConnection(this);
    }
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java.net.HttpURLConnection部分源码:

abstract public class HttpURLConnection extends URLConnection {
    // ...
}
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从代码可知HttpURLConnection是URLConnection子类, 其内类中主要放置的是一些父类的方法和请求码信息.

发送GET请求, 其主要的参数从URI中获取,还有请求头,cookies等数据.

发送POST请求, HttpURLConnection实例必须设置setDoOutput(true),其请求体数据写入由HttpURLConnection的getOutputStream()方法返回的输出流来传输数据.

1 准备一个SpringBoot项目环境

2 添加一个控制器

@Controller
@Slf4j
public class HelloWorld {

    @Override
    @GetMapping("/world/getData")
    @ResponseBody
    public String getData(@RequestParam Map<String, Object> param) {
        System.out.println(param.toString());
        return "<h1> Hello World  getData 方法</h1>";
    }

    @PostMapping("/world/getResult")
    @ResponseBody
    public String getResult(@RequestBody Map<String, Object> param) {
        System.out.println(param.toString());
        return "<h1> Hello World  getResult 方法</h1>";
    }
}
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3 添加一个发送请求的工具类

package com.cf.demo.http;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;

/**
 * Http请求工具类
 */
@Slf4j
@Data
public class JdkHttpUtils {

    /**
     * 获取 POST请求
     *
     * @return 请求结果
     */
    public static String getPost(String url, Integer connectTimeout,
            Integer readTimeout, String contentType, Map<String, String> heads,
            Map<String, String> params) throws IOException {

        URL u;
        HttpURLConnection connection = null;
        OutputStream out;
        try {
            u = new URL(url);
            connection = (HttpURLConnection) u.openConnection();
            connection.setRequestMethod("POST");
            connection.setConnectTimeout(connectTimeout);
            connection.setReadTimeout(readTimeout);
            connection.setRequestProperty("Content-Type", contentType);
            // POST请求必须设置该属性
            connection.setDoOutput(true);
            connection.setDoInput(true);
            if (heads != null) {
                for (Map.Entry<String, String> stringStringEntry : heads.entrySet()) {
                    connection.setRequestProperty(stringStringEntry.getKey(),
                            stringStringEntry.getValue());
                }
            }

            out = connection.getOutputStream();
            if (params != null && !params.isEmpty()) {
                out.write(toJSONString(params).getBytes());
            }
            out.flush();
            out.close();

            // 获取请求返回的数据流
            InputStream is = connection.getInputStream();
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            // 封装输入流is，并指定字符集
            int i;
            while ((i = is.read()) != -1) {
                baos.write(i);
            }
            return baos.toString();

        } catch (Exception e) {
            log.error("请求发生异常,信息为= {} ", e.getMessage());
        }
        return null;
    }


    /**
     * 获取 POST请求
     *
     * @return 请求结果
     */
    public static String getGet(String url, Integer connectTimeout,
            Integer readTimeout, String contentType, Map<String, String> heads,
            Map<String, String> params) throws IOException {

        // 拼接请求参数
        if (params != null && !params.isEmpty()) {
            url += "?";
            if (params != null && !params.isEmpty()) {
                StringBuilder sb = new StringBuilder();
                for (Map.Entry<String, String> stringObjectEntry : params.entrySet()) {
                    try {
                        sb.append(stringObjectEntry.getKey()).append("=").append(
                                URLEncoder.encode(stringObjectEntry.getValue(), "UTF-8"))
                                .append("&");
                    } catch (UnsupportedEncodingException e) {
                        e.printStackTrace();
                    }
                }
                sb.delete(sb.length() - 1, sb.length());
                url += sb.toString();
            }
        }

        URL u;
        HttpURLConnection connection;
        u = new URL(url);
        connection = (HttpURLConnection) u.openConnection();
        connection.setRequestMethod("GET");
        connection.setConnectTimeout(connectTimeout);
        connection.setReadTimeout(readTimeout);
        connection.setRequestProperty("Content-Type", contentType);
        if (heads != null) {
            for (Map.Entry<String, String> stringStringEntry : heads.entrySet()) {
                connection.setRequestProperty(stringStringEntry.getKey(),
                        stringStringEntry.getValue());
            }
        }

        // 获取请求返回的数据流
        InputStream is = connection.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        // 封装输入流is，并指定字符集
        int i;
        while ((i = is.read()) != -1) {
            baos.write(i);
        }
        return baos.toString();

    }


    /**
     * Map转Json字符串
     */
    public static String toJSONString(Map<String, String> map) {
        Iterator<Entry<String, String>> i = map.entrySet().iterator();
        if (!i.hasNext()) {
            return "{}";
        }

        StringBuilder sb = new StringBuilder();
        sb.append('{');
        for (; ; ) {
            Map.Entry<String, String> e = i.next();
            String key = e.getKey();
            String value = e.getValue();
            sb.append("\"");
            sb.append(key);
            sb.append("\"");
            sb.append(':');
            sb.append("\"");
            sb.append(value);
            sb.append("\"");
            if (!i.hasNext()) {
                return sb.append('}').toString();
            }
            sb.append(',').append(' ');
        }
    }


}
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4 添加测试工具类

@Slf4j
public class HttpTest {

    // 请求地址
    public String url = "";
    // 请求头参数
    public Map<String, String> heads = new HashMap<>();
    // 请求参数
    public Map<String, String> params = new HashMap<>();
    // 数据类型
    public String contentType = "application/json";
    // 连接超时
    public Integer connectTimeout = 15000;
    // 读取超时
    public Integer readTimeout = 60000;

    @Test
    public void testGET() {
        // 1 添加数据
        url = "http://localhost:8080/world/getData";
        heads.put("token", "hhhhhhhhhhhaaaaaaaa");
        params.put("username", "libai");

        String result = null;
        try {
            // 2 发送Http请求,获取返回结果
            result = JdkHttpUtils
                    .getGet(url, connectTimeout, readTimeout, contentType, heads, params);
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 3 打印结果
        log.info(result);
    }

    @Test
    public void testPOST() {
        // 1 添加数据
        url = "http://localhost:8080/world/getResult";
        heads.put("token", "hhhhhhhhhhhaaaaaaaa");
        params.put("username", "libai");

        String result = null;
        try {
            // 2 发送Http请求,获取返回结果
            result = JdkHttpUtils
                    .getPost(url, connectTimeout, readTimeout, contentType, heads, params);
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 3 打印结果
        log.info(result);
    }
}    
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5 测试结果

POST请求测试结果

/*
[main] INFO com.cf.demo.HttpTest - <h1> Hello World  getResult 方法</h1>

{username=libai}
*/
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GET请求测试结果

/*
[main] INFO com.cf.demo.HttpTest - <h1> Hello World  getData方法</h1>
    
{username=libai}

*/
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参考资料:

Java中发送Http请求之HttpURLConnection