JAVA内调取API地址的三种方法

1、

import org.apache.commons.io.IoUtils;
import java.net.URL;

URL url = new URL(mainUrl+"/api/getReportFile.action?oldReportCode="+oldReportCode);
InputStream in2 = url.openStream();
String xmlData = IoUtils.toString(in, "UTF-8");

2、

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.http.HttpStatus;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
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;

import com.alibaba.fastjson.JSONObject;

/**
 * @http client请求工具类
 */
public class HttpUtil {
	
	public static String post(String url,Map<String,String> param) throws ParseException, IOException {
		//响应的请求数据
		String result = "";
		//创建HttpClent对象
		CloseableHttpClient httpClient = HttpClients.createDefault();
		//创建Post方式请求对象
		HttpPost httpPost = new HttpPost(url);
		//装填参数
		List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
		if(null != param) {
			for(Entry<String,String> entry : param.entrySet()) {
				nameValuePairs.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
			}
		}
		//设置参数到请求对象中
		httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs,"UTF-8"));
		//设置请求头
		httpPost.setHeader("Content-type", "application/x-www-form-urlencoded");
		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 = httpClient.execute(httpPost);
        
        // 获取结果实体
        // 判断网络连接状态码是否正常(0--200都数正常)
        if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
            String res = EntityUtils.toString(response.getEntity(), "UTF-8");
            JSONObject json = JSONObject.parSEObject(res);
            json = json.getJSONObject("data");
            result = json.toJSONString();
        }
        // 释放链接
        response.close();
		return result;
	}
	
	public static String get(String url) throws ClientProtocolException, IOException {
		String result = "";
		// 创建httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        // 创建get方式请求对象
        HttpGet httpGet = new HttpGet(url);
        httpGet.addHeader("Content-type", "application/json");
        // 通过请求对象获取响应对象
        CloseableHttpResponse response = httpClient.execute(httpGet);
        // 获取结果实体
        // 判断网络连接状态码是否正常(0--200都数正常)
        if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
            result = EntityUtils.toString(response.getEntity(), "UTF-8");
        }
        // 释放链接
        response.close();
        return result;
	}

}

3、参考：https://www.cnblogs.com/chzhq/p/8665989.html
https://blog.csdn.net/u014181912/article/details/84838575

测试例子：

@RequestMapping(value = "/api/messenger/getReportFile.action")
public void getReportFile(HttpServletRequest request, HttpServletResponse response) throws Exception {
	HashMap<String, Object> map = new HashMap<>();
	try {
		String oldReportCode = request.getParameter("oldReportCode");
		List<ReportFileEntity> reportFileDs = reportFileDao.selectByCodeAndSort(oldReportCode, 1);
		String json = JSONObject.toJSONString(reportFileDs);
		map.put("json", json);
	} catch (Exception e) {
		map.put("msg", "报错信息：" + CommonUtil.getExceptionDetail(e));
	}
	String result = XmlUtil.map2Xml(map);
	PrintWriter  out = null;
	try {
		out = response.getWriter();
		out.write(result);
		out.flush();
	} catch (IOException e) {
		e.printstacktrace();
	} finally {
		if (out != null) {
			out.close();
		}
	}
}


import com.alibaba.fastjson.JSON;

public static String mainUrl = "http://localhost:8003";


List<ReportFileEntity> reportFileDs = (List<ReportFileEntity>) this.getUrlData(mainUrl+"/api/messenger/getReportFile.action?oldReportCode="+oldReportCode, 
						ReportFileEntity.class);
						

public <T> List<T> getUrlData(String url, Class<T> type) throws Exception{
		String xmlData = HttpUtil.get(url);
		Map<String, Object> mapData = XmlUtil.xml2Map(xmlData);
		String msgData = (String) mapData.get("msg");
		if(msgData != null && msgData != "") {
			throw new Exception(msgData);
		}
		String jsonData = (String) mapData.get("json");
		//将json转化成指定实体类的list
		List<T> result = new ArrayList<T>();
		if(jsonData != null) {
			result = JSON.parseArray(jsonData, type);
		}
		return result;
	}