主要使用的jar包有httpclient-4.5.3.jar、httpcore-4.4.6.jar、commons-codec-1.9.jar、gson-2.2.4.jar和commons-logging-1.2.jar。

　 如果傳送的post請求想傳送檔案，需新增httpmime-4.5.3.jar包，並設定如下程式碼：

    HttpEntity multipartEntityBuilder = MultipartEntityBuilder.create().addBinaryBody("file", new File("D:\\workspace\\programm\\WebContent\\programm\\1991.zip")).build();

    第一個引數表示請求欄位名，第二個引數就是檔案。

    還想新增引數則

    HttpEntity multipartEntityBuilder = MultipartEntityBuilder.create().addTextBody("name", "張三").addBinaryBody("file", new File("D:\\workspace\\programm\\WebContent\\programm\\1991.zip")).build();

    httpPost.setEntity(multipartEntityBuilder);

import java.io.IOException;
 
import java.util.Map;

import org.apache.http.HttpEntity;
import org.apache.http.client.ClientProtocolException;
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.util.EntityUtils;

import com.google.gson.Gson;

public class HttpClientUtil {
    
    private final static String CONTENT_TYPE_TEXT_JSON = "text/json";
    
    public static String postRequest(String url, Map<String, Object> param) throws ClientProtocolException, IOException{
        
        CloseableHttpClient client = HttpClients.createDefault();

        HttpPost httpPost = new HttpPost(url);
        httpPost.setHeader("Content-Type", "application/json;charset=UTF-8");
        
        Gson gson = new Gson();
        String parameter = gson.toJson(param);

        StringEntity se = new StringEntity(parameter);
        se.setContentType(CONTENT_TYPE_TEXT_JSON);
        httpPost.setEntity(se);

        CloseableHttpResponse response = client.execute(httpPost);
        HttpEntity entity = response.getEntity();
        String result = EntityUtils.toString(entity, "UTF-8");
        
        return result;
    }

}

 2、返回的結果也可以使用gson轉換成物件進行下一步操作。

import com.google.gson.Gson;

public class GsonUtil {

    public static <T> T jsonToObject(String jsonData, Class<T> type) {
        Gson gson = new Gson();
        T result = gson.fromJson(jsonData, type);
        return result;
    }
    
    public static void main(String[] args) {
        String json = "{'id':'1','name':'zhang','address':'Hubei'}";
        jsonToObject(json, Person.class);
        Person person = jsonToObject(json, Person.class);
        System.out.println(person);
    }

}

建立要轉成的物件的類。

import java.util.Date;

public class Person {
    
    private int id;
    
    private String name;
    
    private int age;
    
    private String address;public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "Person [id=" + id + ", name=" + name + ", age=" + age + ", address=" + address + "]";
    }

}

 3、傳送以鍵值對形式的引數的post請求

package com.avatarmind.httpclient;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

public class HttpClient3 {
    
    public static void main(String[] args) throws Exception {
        CloseableHttpClient client = HttpClients.createDefault();

        String url = "http://yuntuapi.amap.com/datamanage/table/create";

        HttpPost httpPost = new HttpPost(url);

        // 引數形式為key=value&key=value
        List<NameValuePair> formparams = new ArrayList<NameValuePair>();
        formparams.add(new BasicNameValuePair("key", "060212638b94290e3dd0648c15753b64"));
        formparams.add(new BasicNameValuePair("name", "火狐"));
                
        // 加utf-8進行編碼
        UrlEncodedFormEntity uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
        httpPost.setEntity(uefEntity);

        CloseableHttpResponse response = client.execute(httpPost);
        HttpEntity entity = response.getEntity();
        String result = EntityUtils.toString(entity, "UTF-8");
        System.out.println(result);
    }

}