Java Post请求工具类，非常实用，建议收藏（非常实用的plc入门教程）

核心代码：

import java.util.Map;
import java.util.List;
import java.util.Iterator;
import java.util.ArrayList;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;
import java.io.ByteArrayOutputStream;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHeaders;
import org.apache.http.HttpResponse;
import org.apache.http.util.EntityUtils;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;

/**
 * Post请求工具类
 */
public class PostUtil {
    public static final String UTF8 = "utf-8";
    private static final String CONTENT_TYPE = "application/json";

    public static String send(String url, Map<String, String> headers, Object params) {
        try {
            if (params instanceof Map)
                return sendMap(url, headers, (Map<String, Object>)params);
            else
                return sendJson(url, headers, (String)params);
        } catch (Exception e){
            return null;
        }
    }

    public static String sendMap(String url, Map<String, String> headers, Map<String, Object> params) throws IOException {
        List<BasicNameValuePair> pairs = new ArrayList<>();
        for (Iterator<String> iterator = params.keySet().iterator(); iterator.hasNext();) {
            String name = iterator.next();
            Object value = params.get(name);
            pairs.add(new BasicNameValuePair(name, String.valueOf(value)));
        }

        UrlEncodedFormEntity entity = new UrlEncodedFormEntity(pairs, UTF8);
        return doAction(url, headers, entity);
    }

    public static String sendJson(String url, Map<String, String> headers, String params) throws IOException {
        StringEntity entity = new StringEntity(params, UTF8);
        return doAction(url, headers, entity);
    }

    private static String doAction(String url, Map<String, String> headers, StringEntity body) throws IOException {
        HttpPost post = new HttpPost(url);
        post.setEntity(body);
        for (String key : headers.keySet())
            post.addHeader(key, headers.get(key));

        CloseableHttpClient client = HttpClients.createDefault();
        CloseableHttpResponse response = client.execute(post);
        HttpEntity entity = response.getEntity();

        String result = null;
        if (entity != null)
            result = EntityUtils.toString(entity, UTF8);

        response.close();
        return result;
    }

    /**
     * 发送 POST JSON 请求
     */
    public static String postJson(String url, String data) {
        HttpClientBuilder builder = HttpClientBuilder.create();
        HttpUriRequest request = null;
        // POST请求
        HttpEntity entity = new StringEntity(data, UTF8);
        HttpPost post = new HttpPost(url);
        post.setEntity(entity);
        request = post;
        request.setHeader(HttpHeaders.CONTENT_TYPE, CONTENT_TYPE);
        try (CloseableHttpClient closeableHttpClient = builder.build()) {
            HttpResponse resp = closeableHttpClient.execute(request);
            InputStream respIs = resp.getEntity().getContent();
            byte[] respBytes = toByteArray(respIs);
            String result = new String(respBytes, Charset.forName(UTF8));
            return result;
        } catch (Exception e) {
            e.printStackTrace();
        }

        return null;
    }

    private static byte[] toByteArray(InputStream is) throws IOException {
        ByteArrayOutputStream output = new ByteArrayOutputStream();

        try {
            byte[] b = new byte[4096];
            boolean var3 = false;

            int n;
            while ((n = is.read(b)) != -1) {
                output.write(b, 0, n);
            }

            byte[] var4 = output.toByteArray();
            return var4;
        } finally {
            output.close();
        }
    }
}

路漫漫其修远兮，吾将上下而求索

译文：在追寻真理方面，前方的道路还很漫长，但我将百折不挠，不遗余力地去追求和探索。

如果您有什么好的想法与方法，欢迎在评论区留言，我们一起讨论~