Java发送POST请求，并接收返回JSON数据

1.请求参数为json格式

1.pom.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>tcl.java</groupId>
    <artifactId>test</artifactId>
    <version>1.0-SNAPSHOT</version>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>hello.helloword</mainClass>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
    <dependencies>

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.5</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.51</version>
        </dependency>
    </dependencies>

</project>

2.代码

package hello;

import com.alibaba.fastjson.JSONObject;
import org.apache.http.HttpEntity;
import org.apache.http.ParseException;
import org.apache.http.client.methods.CloseableHttpResponse;
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.message.BasicHeader;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;


import java.io.IOException;
import java.util.HashMap;

public class JsonPost {
    /**
     * 发送post请求
     * @param url  路径
     * @param jsonObject  参数(json类型)
     * @param encoding 编码格式
     * @return
     * @throws ParseException
     * @throws IOException
     */
    public static String send(String url, JSONObject jsonObject, String encoding) throws ParseException, IOException {
        String body = "";

        //创建httpclient对象
        CloseableHttpClient client = HttpClients.createDefault();
        //创建post方式请求对象
        HttpPost httpPost = new HttpPost(url);

        //装填参数
        StringEntity s = new StringEntity(jsonObject.toString(), "utf-8");
        s.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE,
                "application/json"));
        //设置参数到请求对象中
        httpPost.setEntity(s);
//        System.out.println("请求地址："+url);
//        System.out.println("请求参数："+nvps.toString());

        //设置header信息
        //指定报文头【Content-type】、【User-Agent】
//        httpPost.setHeader("Content-type", "application/x-www-form-urlencoded");
        httpPost.setHeader("Content-type", "application/json");
        httpPost.setHeader("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");

        //执行请求操作，并拿到结果（同步阻塞）
        CloseableHttpResponse response = client.execute(httpPost);
        //获取结果实体
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            //按指定编码转换结果实体为String类型
            body = EntityUtils.toString(entity, encoding);
        }
        EntityUtils.consume(entity);
        //释放链接
        response.close();
        return body;
    }

    public static void main(String[] args) throws IOException {
//        将post请求参数写到map中（map中可以存map）
        HashMap<String, String> params = new HashMap<>();
        params.put("date", "20200630");
        params.put("typeId", "dsafa");
        HashMap<String, Object> map = new HashMap<>();
        map.put("key", "42423=q8");
        map.put("id", "42342352");
        map.put("pageNum", "0");
        map.put("pageSize", "1000");
        map.put("params", params);
//        将map转为json对象
        JSONObject json = new JSONObject(map);
        String  url = "http://dc-o.web.leiniao.com/operation/open/request";
        System.out.println(send(url, json, "UTF-8"));
    }
}

2.请求参数为form-data格式

1.pom.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>tcl.java</groupId>
    <artifactId>test</artifactId>
    <version>1.0-SNAPSHOT</version>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>hello.helloword</mainClass>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
    <dependencies>

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.5</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.51</version>
        </dependency>
    </dependencies>

</project>

2.代码

package hello;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;

public class FormatPost {
    /**
     * 使用POST格式发送form-data格式参数，并获取响应字符串
     * @param path
     * @param params
     * @return
     */
    public static String sendSmsFormByPost(String path, Map<String ,Object> params){
        URL u = null;
        HttpURLConnection con = null;
        // 构建请求参数
        StringBuffer sb = new StringBuffer();
        if (params != null) {
            for (Map.Entry<String, Object> e : params.entrySet()) {
                sb.append(e.getKey());
                sb.append("=");
                sb.append(e.getValue());
                sb.append("&");
            }
            //去掉最后一个&
            sb.substring(0, sb.length() - 1);
        }
        // 尝试发送请求
        try {
            u = new URL(path);
            con = (HttpURLConnection) u.openConnection();
            //// POST 只能为大写，严格限制，post会不识别
            con.setRequestMethod("POST");
            con.setDoOutput(true);
            con.setDoInput(true);
            con.setUseCaches(false);
            con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            OutputStreamWriter osw = new OutputStreamWriter(con.getOutputStream(), "UTF-8");
            osw.write(sb.toString());
            osw.flush();
            osw.close();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (con != null) {
                con.disconnect();
            }
        }

        // 读取返回内容
        StringBuffer buffer = new StringBuffer();
        try {
            //一定要有返回值，否则无法把请求发送给server端。
            BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream(), "UTF-8"));
            String temp;
            while ((temp = br.readLine()) != null) {
                buffer.append(temp);
                buffer.append("\n");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return buffer.toString();
    }


        public static void main(String[] args) throws IOException {
//        将post请求参数写到map中
            HashMap<String, Object> map = new HashMap<>();
            map.put("key", "rwrwffcs");
            map.put("id", "424252");
            map.put("pageNum", "0");
            map.put("pageSize", "1000");
            map.put("params", "aaa");
            String  url = "http://dc-o.web.leiniao.com/operation/open/request";
            System.out.println(sendSmsFormByPost(url, map));
        
    }
    
    
}