使用HttpClient访问接口（Rest接口和普通接口）

这里总结一下使用HttpClient访问外部接口的用法。后期如果发现有什么缺陷会更改。欢迎读者指出此方法的不足之处。

首先，创建一个返回实体：

public class HttpResult {
    // 响应的状态码
    private int code;

    // 响应的响应体
    private String body;

    public HttpResult(int code, String body) {
        this.code = code;
        this.body = body;
    }
	//省略get/set
}

创建一个HttpClientUtil：

public class HttpClientUtil {

    private static CloseableHttpClient httpClient =  HttpClients.createDefault();	//用static实现单例，此处不完善，当多线程时会出现问题。

    /**
     * 带参数的get请求
     * 
     * @param url
     * @param map
     * @return
     * @throws Exception
     */
    public static HttpResult doGet(String url, Map<String, Object> map) throws Exception {

        // 声明URIBuilder
        URIBuilder uriBuilder = new URIBuilder(url);

        // 判断参数map是否为非空
        if (map != null) {
            // 遍历参数
            for (Map.Entry<String, Object> entry : map.entrySet()) {
                // 设置参数
                uriBuilder.setParameter(entry.getKey(), entry.getValue().toString());
            }
        }

        // 2 创建httpGet对象，相当于设置url请求地址
        HttpGet httpGet = new HttpGet(uriBuilder.build());

        // 3 使用HttpClient执行httpGet，相当于按回车，发起请求
        CloseableHttpResponse response = httpClient.execute(httpGet);

        // 4 解析结果，封装返回对象httpResult，相当于显示相应的结果
        // 状态码
        // response.getStatusLine().getStatusCode();
        // 响应体，字符串，如果response.getEntity()为空，下面这个代码会报错,所以解析之前要做非空的判断
        // EntityUtils.toString(response.getEntity(), "UTF-8");
        HttpResult httpResult = null;
        // 解析数据封装HttpResult
        if (response.getEntity() != null) {
            httpResult = new HttpResult(response.getStatusLine().getStatusCode(),
                    EntityUtils.toString(response.getEntity(), "UTF-8"));
        } else {
            httpResult = new HttpResult(response.getStatusLine().getStatusCode(), "");
        }

        // 返回
        return httpResult;
    }

    /**
     * 不带参数的get请求
     * 
     * @param url
     * @return
     * @throws Exception
     */
    public static HttpResult doGet(String url) throws Exception {
        HttpResult httpResult = doGet(url, null);
        return httpResult;
    }

    /**
     * 带参数的post请求
     * 
     * @param url
     * @return
     * @throws Exception
     */
    public static HttpResult doPost(String url, Map<String, Object> reqMap, Map<String,String> headersMap) throws Exception {
        // 声明httpPost请求
        HttpPost httpPost = new HttpPost(url);
        for (Map.Entry<String, String> entry: headersMap.entrySet())
            httpPost.addHeader(entry.getKey(), entry.getValue());

        // 判断map不为空
        if (reqMap != null) {

            // 创建form表单对象
            StringEntity formEntity = new StringEntity(JSON.toJSONString(reqMap), "UTF-8");

            // 把表单对象设置到httpPost中
            httpPost.setEntity(formEntity);
        }

        // 使用HttpClient发起请求，返回response
        CloseableHttpResponse response = httpClient.execute(httpPost);

        // 解析response封装返回对象httpResult
        HttpResult httpResult = null;
        if (response.getEntity() != null) {
            httpResult = new HttpResult(response.getStatusLine().getStatusCode(),
                    EntityUtils.toString(response.getEntity(), "UTF-8"));
        } else {
            httpResult = new HttpResult(response.getStatusLine().getStatusCode(), "");
        }

        // 返回结果
        return httpResult;
    }

    /**
     * 不带参数的post请求
     * 
     * @param url
     * @return
     * @throws Exception
     */
    public static HttpResult doPost(String url) throws Exception {
        HttpResult httpResult = doPost(url, null,null);
        return httpResult;
    }

    /**
     * 带参数的Put请求
     * 
     * @param url
     * @param map
     * @return
     * @throws Exception
     */
    public static HttpResult doPut(String url, Map<String, Object> map) throws Exception {
        // 声明httpPost请求
        HttpPut httpPut = new HttpPut(url);

        // 判断map不为空
        if (map != null) {
            // 声明存放参数的List集合
            List<NameValuePair> params = new ArrayList<NameValuePair>();

            // 遍历map，设置参数到list中
            for (Map.Entry<String, Object> entry : map.entrySet()) {
                params.add(new BasicNameValuePair(entry.getKey(), entry.getValue().toString()));
            }

            // 创建form表单对象
            UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(params, "UTF-8");

            // 把表单对象设置到httpPost中
            httpPut.setEntity(formEntity);
        }

        // 使用HttpClient发起请求，返回response
        CloseableHttpResponse response = httpClient.execute(httpPut);

        // 解析response封装返回对象httpResult
        HttpResult httpResult = null;
        if (response.getEntity() != null) {
            httpResult = new HttpResult(response.getStatusLine().getStatusCode(),
                    EntityUtils.toString(response.getEntity(), "UTF-8"));
        } else {
            httpResult = new HttpResult(response.getStatusLine().getStatusCode(), "");
        }

        // 返回结果
        return httpResult;
    }

    /**
     * 带参数的Delete请求
     * 
     * @param url
     * @param map
     * @return
     * @throws Exception
     */
    public static HttpResult doDelete(String url, Map<String, Object> map) throws Exception {

        // 声明URIBuilder
        URIBuilder uriBuilder = new URIBuilder(url);

        // 判断参数map是否为非空
        if (map != null) {
            // 遍历参数
            for (Map.Entry<String, Object> entry : map.entrySet()) {
                // 设置参数
                uriBuilder.setParameter(entry.getKey(), entry.getValue().toString());
            }
        }

        // 2 创建httpGet对象，相当于设置url请求地址
        HttpDelete httpDelete = new HttpDelete(uriBuilder.build());

        // 3 使用HttpClient执行httpGet，相当于按回车，发起请求
        CloseableHttpResponse response = httpClient.execute(httpDelete);

        // 4 解析结果，封装返回对象httpResult，相当于显示相应的结果
        // 状态码
        // response.getStatusLine().getStatusCode();
        // 响应体，字符串，如果response.getEntity()为空，下面这个代码会报错,所以解析之前要做非空的判断
        // EntityUtils.toString(response.getEntity(), "UTF-8");
        HttpResult httpResult = null;
        // 解析数据封装HttpResult
        if (response.getEntity() != null) {
            httpResult = new HttpResult(response.getStatusLine().getStatusCode(),
                    EntityUtils.toString(response.getEntity(), "UTF-8"));
        } else {
            httpResult = new HttpResult(response.getStatusLine().getStatusCode(), "");
        }

        // 返回
        return httpResult;
    }

    /**
     * 返回常用请求头
     * @return
     */
    public static Map<String, String> commentHeader(){
        Map<String, String> map = new HashMap<>();
        map.put("Content-Type", "application/json");
        return map;
    }
}

测试一下：

package cn.xxxxxx.httpclient.test;

import java.util.HashMap;
import java.util.Map;

import org.junit.Before;
import org.junit.Test;

import cn.itcast.httpclient.APIService;
import cn.itcast.httpclient.HttpResult;

public class APIServiceTest {

    // 查询
    @Test
    public void testGet() throws Exception {
        // http://manager.aaaaaa.com/rest/item/interface/{id}

        String url = "http://manager.aaaaaa.com/rest/item/interface/42";

        HttpResult httpResult = HttpClientUtil.doGet(url);

        System.out.println(httpResult.getCode());
        System.out.println(httpResult.getBody());

    }

	// 查询
    @Test
    public void testPost() throws Exception {
      	//设置参数
        Map reqMap = new HashMap();
		reqMap.put("distCode", arsArg.getDistCode());
		HttpResult httpResult = null;
		try {
          	//RestUrlsCommons.RMDS_DISTRICT_FINDBYDISTCODE为url
          	//reqMap：请求参数
          	//HttpClientUtil.commentHeader()：请求头
			httpResult = HttpClientUtil.doPost(RestUrlsCommons.RMDS_DISTRICT_FINDBYDISTCODE, reqMap, HttpClientUtil.commentHeader());
		} catch (Exception e) {
			e.printStackTrace();
		}

        System.out.println(httpResult.getCode());
        System.out.println(httpResult.getBody());
    }

}

---

参考资料：使用HttpClient调用接口