java 访问url

在平时开发中，我们一般都需要实现外部的url，贴上本人开发使用的三种访问代码。希望点评

第一种：

public class HttpUtils {public static void main(String[] args) {System.out.println(SMS("", "https://www.baidu.com/"));}private static String SMS(String postData, String postUrl) {try {// 发送POST请求URL url = new URL(postUrl);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("POST");//修改发送方式conn.setRequestProperty("Content-Type","application/x-www-form-urlencoded");conn.setRequestProperty("Connection", "Keep-Alive");conn.setUseCaches(false);conn.setDoOutput(true);conn.setRequestProperty("Content-Length", "" + postData.length());OutputStreamWriter out = new OutputStreamWriter(conn.getOutputStream(), "UTF-8");out.write(postData);out.flush();out.close();// 获取响应状态if (conn.getResponseCode() != HttpURLConnection.HTTP_OK) {return "";}// 获取响应内容体String line, result = "";BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "utf-8"));while ((line = in.readLine()) != null) {result += line + "\n";}in.close();return result;} catch (IOException e) {}return "";}}

第二种，跟第一种类似，进行了细化：

import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.io.UnsupportedEncodingException;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.ProtocolException;import java.net.URL;import java.net.URLEncoder;import java.util.Iterator;import java.util.Map;import java.util.Map.Entry;public class HttpUtils {private static final int TIME_OUT = 5;/** * 通过HTTP GET 发送参数 *  * @param httpUrl * @param parameter * @param httpMethod */public static String sendGet(String httpUrl, Map<String, String> parameter) {if (parameter == null || httpUrl == null) {return null;}StringBuilder sb = new StringBuilder();Iterator<Map.Entry<String, String>> iterator = parameter.entrySet().iterator();while (iterator.hasNext()) {if (sb.length() > 0) {sb.append('&');}Entry<String, String> entry = iterator.next();String key = entry.getKey();String value;try {value = URLEncoder.encode(entry.getValue(), "UTF-8");} catch (UnsupportedEncodingException e) {value = "";}sb.append(key).append('=').append(value);}String urlStr = null;if (httpUrl.lastIndexOf('?') != -1) {urlStr = httpUrl + '&' + sb.toString();} else {urlStr = httpUrl + '?' + sb.toString();}HttpURLConnection httpCon = null;String responseBody = null;try {URL url = new URL(urlStr);httpCon = (HttpURLConnection) url.openConnection();httpCon.setDoOutput(true);httpCon.setRequestMethod("GET");httpCon.setConnectTimeout(TIME_OUT * 1000);httpCon.setReadTimeout(TIME_OUT * 1000);// 开始读取返回的内容InputStream in = httpCon.getInputStream();byte[] readByte = new byte[1024];// 读取返回的内容int readCount = in.read(readByte, 0, 1024);ByteArrayOutputStream baos = new ByteArrayOutputStream();while (readCount != -1) {baos.write(readByte, 0, readCount);readCount = in.read(readByte, 0, 1024);}responseBody = new String(baos.toByteArray(), "UTF-8");baos.close();} catch (Exception e) {} finally {if (httpCon != null)httpCon.disconnect();}return responseBody;}/** * 使用HTTP POST 发送文本 *  * @param httpUrl *            发送的地址 * @param postBody *            发送的内容 * @return 返回HTTP SERVER的处理结果,如果返回null,发送失败 */public static String sentPost(String httpUrl, String postBody) {return sentPost(httpUrl, postBody, "UTF-8", null);}/** * 使用HTTP POST 发送文本 *  * @param httpUrl *            发送的地址 * @param postBody *            发送的内容 * @return 返回HTTP SERVER的处理结果,如果返回null,发送失败 */public static String sentPost(String httpUrl, String postBody, String encoding) {return sentPost(httpUrl, postBody, encoding, null);}/** * 使用HTTP POST 发送文本 * @param httpUrl   目的地址 * @param postBody  post的包体 * @param headerMap 增加的Http头信息 * @return */public static String sentPost(String httpUrl, String postBody, Map<String, String> headerMap) {return sentPost(httpUrl, postBody, "UTF-8", headerMap);}/** * 使用HTTP POST 发送文本 *  * @param httpUrl *            发送的地址 * @param postBody *            发送的内容 * @param encoding *            发送的内容的编码 * @param headerMap 增加的Http头信息           * @return 返回HTTP SERVER的处理结果,如果返回null,发送失败 * ................. */public static String sentPost(String httpUrl, String postBody, String encoding, Map<String, String> headerMap) {HttpURLConnection httpCon = null;String responseBody = null;URL url = null;try {url = new URL(httpUrl);} catch (MalformedURLException e1) {return null;}try {httpCon = (HttpURLConnection) url.openConnection();} catch (IOException e1) {return null;}if (httpCon == null) {return null;}httpCon.setDoOutput(true);httpCon.setConnectTimeout(TIME_OUT * 1000);httpCon.setReadTimeout(TIME_OUT * 1000);httpCon.setDoOutput(true);httpCon.setUseCaches(false);try {httpCon.setRequestMethod("POST");} catch (ProtocolException e1) {return null;}if (headerMap != null) {Iterator<Entry<String, String>> iterator = headerMap.entrySet().iterator();while (iterator.hasNext()) {Entry<String, String> entry = iterator.next();httpCon.addRequestProperty(entry.getKey(), entry.getValue());}}OutputStream output;try {output = httpCon.getOutputStream();} catch (IOException e1) {return null;}try {output.write(postBody.getBytes(encoding));} catch (UnsupportedEncodingException e1) {return null;} catch (IOException e1) {return null;}try {output.flush();output.close();} catch (IOException e1) {return null;}// 开始读取返回的内容InputStream in;try {in = httpCon.getInputStream();} catch (IOException e1) {return null;}/** * 这个方法可以在读写操作前先得知数据流里有多少个字节可以读取。 * 需要注意的是，如果这个方法用在从本地文件读取数据时，一般不会遇到问题， * 但如果是用于网络操作，就经常会遇到一些麻烦。 * 比如，Socket通讯时，对方明明发来了1000个字节，但是自己的程序调用available()方法却只得到900，或者100，甚至是0， * 感觉有点莫名其妙，怎么也找不到原因。 * 其实，这是因为网络通讯往往是间断性的，一串字节往往分几批进行发送。 * 本地程序调用available()方法有时得到0，这可能是对方还没有响应，也可能是对方已经响应了，但是数据还没有送达本地。 * 对方发送了1000个字节给你，也许分成3批到达，这你就要调用3次available()方法才能将数据总数全部得到。 *  * 经常出现size为0的情况，导致下面readCount为0使之死循环(while (readCount != -1) {xxxx})，出现死机问题 */int size = 0;try {size = in.available();} catch (IOException e1) {return null;}if (size == 0) {size = 1024;}byte[] readByte = new byte[size];// 读取返回的内容int readCount = -1;try {readCount = in.read(readByte, 0, size);} catch (IOException e1) {return null;}ByteArrayOutputStream baos = new ByteArrayOutputStream();while (readCount != -1) {baos.write(readByte, 0, readCount);try {readCount = in.read(readByte, 0, size);} catch (IOException e) {return null;}}try {responseBody = new String(baos.toByteArray(), encoding);} catch (UnsupportedEncodingException e) {return null;} finally {if (httpCon != null) {httpCon.disconnect();}if (baos != null) {try {baos.close();} catch (IOException e) {}}}return responseBody;}}

第三种，使用httpclient进行访问，需要是到  http://hc.apache.org/下载jar包

import java.io.IOException;import org.apache.http.HttpEntity;import org.apache.http.HttpResponse;import org.apache.http.client.ClientProtocolException;import org.apache.http.client.ResponseHandler;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.util.EntityUtils;/** * 根据httpclient进行访问 * @author Administrator * */public class HttpUtils {/** * 访问url方法 *  * @param url * @return */public static String callOnHttp(String url) {String address = "";CloseableHttpClient httpclient = HttpClients.createDefault();try {HttpGet httpget = new HttpGet(url);ResponseHandler<String> responseHandler = new ResponseHandler<String>() {public String handleResponse(final HttpResponse response)throws ClientProtocolException, IOException {int status = response.getStatusLine().getStatusCode();if (status >= 200 && status < 300) {HttpEntity entity = response.getEntity();return entity != null ? EntityUtils.toString(entity): null;} else {throw new ClientProtocolException("Unexpected response status: " + status);}}};address = httpclient.execute(httpget, responseHandler);} catch (Exception e) {e.printStackTrace();} finally {try {httpclient.close();} catch (IOException e) {e.printStackTrace();}}return address;}}