java.net.URLConnection
在这里经常会问到使用的情况,而Oracle教程对此却过于简洁。
该教程基本上仅显示如何触发GET请求并读取响应。它没有任何地方解释如何使用它来执行POST请求,设置请求标头,读取响应标头,处理cookie,提交HTML表单,上传文件等。
因此,如何使用它java.net.URLConnection
来触发和处理“高级” HTTP请求?
java.net.URLConnection
在这里经常会问到使用的情况,而Oracle教程对此却过于简洁。
该教程基本上仅显示如何触发GET请求并读取响应。它没有任何地方解释如何使用它来执行POST请求,设置请求标头,读取响应标头,处理cookie,提交HTML表单,上传文件等。
因此,如何使用它java.net.URLConnection
来触发和处理“高级” HTTP请求?
Answers:
首先先声明一下:发布的代码段都是基本示例。您需要处理琐碎的IOException
s和RuntimeException
s like NullPointerException
,ArrayIndexOutOfBoundsException
然后自己整理。
我们首先至少需要知道URL和字符集。参数是可选的,取决于功能要求。
String url = "http://example.com";
String charset = "UTF-8"; // Or in Java 7 and later, use the constant: java.nio.charset.StandardCharsets.UTF_8.name()
String param1 = "value1";
String param2 = "value2";
// ...
String query = String.format("param1=%s¶m2=%s",
URLEncoder.encode(param1, charset),
URLEncoder.encode(param2, charset));
查询参数的name=value
格式必须为,并由串联&
。通常,您还可以使用指定的字符集对查询参数进行网址编码URLEncoder#encode()
。
该String#format()
只是为方便起见。当我需要String串联运算符+
两次以上时,我更喜欢它。
这是一项微不足道的任务。这是默认的请求方法。
URLConnection connection = new URL(url + "?" + query).openConnection();
connection.setRequestProperty("Accept-Charset", charset);
InputStream response = connection.getInputStream();
// ...
任何查询字符串都应使用串联到URL ?
。该Accept-Charset
标题可能暗示什么编码参数是在服务器中。如果你不发送任何查询字符串,那么你就可以离开了Accept-Charset
头了。如果您不需要设置任何标题,那么甚至可以使用URL#openStream()
快捷方式。
InputStream response = new URL(url).openStream();
// ...
无论哪种方式,如果另一侧是a HttpServlet
,则将doGet()
调用其方法,并且参数将通过提供HttpServletRequest#getParameter()
。
为了进行测试,您可以将响应正文打印到stdout,如下所示:
try (Scanner scanner = new Scanner(response)) {
String responseBody = scanner.useDelimiter("\\A").next();
System.out.println(responseBody);
}
将设置为URLConnection#setDoOutput()
会true
隐式将请求方法设置为POST。与Web表单一样,标准HTTP POST的类型是application/x-www-form-urlencoded
将查询字符串写入请求正文。
URLConnection connection = new URL(url).openConnection();
connection.setDoOutput(true); // Triggers POST.
connection.setRequestProperty("Accept-Charset", charset);
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded;charset=" + charset);
try (OutputStream output = connection.getOutputStream()) {
output.write(query.getBytes(charset));
}
InputStream response = connection.getInputStream();
// ...
注意:每当您要以编程方式提交HTML表单时,请不要忘记将name=value
任何<input type="hidden">
元素对都放入查询字符串中,当然也要将要通过编程“按” name=value
的<input type="submit">
元素对(因为通常用于服务器端,以区分是否按下了按钮,如果按下了,则区分哪个按钮。
您也可以将获得的内容转换URLConnection
为,HttpURLConnection
并改用它HttpURLConnection#setRequestMethod()
。但是,如果您尝试将连接用于输出,则仍需要设置URLConnection#setDoOutput()
为true
。
HttpURLConnection httpConnection = (HttpURLConnection) new URL(url).openConnection();
httpConnection.setRequestMethod("POST");
// ...
无论哪种方式,如果另一侧是a HttpServlet
,则将doPost()
调用其方法,并且参数将通过提供HttpServletRequest#getParameter()
。
您可以使用显式触发HTTP请求URLConnection#connect()
,但是当您想要获取有关HTTP响应的任何信息(例如使用的响应主体等)时,请求将自动按需触发URLConnection#getInputStream()
。上面的示例正是这样做的,因此该connect()
调用实际上是多余的。
您需要HttpURLConnection
这里。如有必要,请先投放。
int status = httpConnection.getResponseCode();
for (Entry<String, List<String>> header : connection.getHeaderFields().entrySet()) {
System.out.println(header.getKey() + "=" + header.getValue());
}
当Content-Type
包含一个charset
参数时,响应主体可能是基于文本的,因此我们想使用服务器端指定的字符编码来处理响应主体。
String contentType = connection.getHeaderField("Content-Type");
String charset = null;
for (String param : contentType.replace(" ", "").split(";")) {
if (param.startsWith("charset=")) {
charset = param.split("=", 2)[1];
break;
}
}
if (charset != null) {
try (BufferedReader reader = new BufferedReader(new InputStreamReader(response, charset))) {
for (String line; (line = reader.readLine()) != null;) {
// ... System.out.println(line) ?
}
}
} else {
// It's likely binary content, use InputStream/OutputStream.
}
服务器端会话通常由cookie支持。某些Web表单要求您登录和/或由会话跟踪。您可以使用CookieHandler
API维护cookie。你需要准备一个CookieManager
具有CookiePolicy
中ACCEPT_ALL
发送所有HTTP请求之前。
// First set the default cookie manager.
CookieHandler.setDefault(new CookieManager(null, CookiePolicy.ACCEPT_ALL));
// All the following subsequent URLConnections will use the same cookie manager.
URLConnection connection = new URL(url).openConnection();
// ...
connection = new URL(url).openConnection();
// ...
connection = new URL(url).openConnection();
// ...
请注意,这并非总是在所有情况下都能正常工作。如果失败了,那么最好是手动收集并设置Cookie标头。基本上,您需要Set-Cookie
从登录或第一个GET
请求的响应中获取所有标头,然后将其传递给后续请求。
// Gather all cookies on the first request.
URLConnection connection = new URL(url).openConnection();
List<String> cookies = connection.getHeaderFields().get("Set-Cookie");
// ...
// Then use the same cookies on all subsequent requests.
connection = new URL(url).openConnection();
for (String cookie : cookies) {
connection.addRequestProperty("Cookie", cookie.split(";", 2)[0]);
}
// ...
该split(";", 2)[0]
是有摆脱它们是无关的服务器端如cookie的属性expires
,path
等等。另外,你也可以使用cookie.substring(0, cookie.indexOf(';'))
替代的split()
。
HttpURLConnection
默认情况下,will会在实际发送请求之前缓冲整个请求正文,无论您是否使用设置了固定的内容长度connection.setRequestProperty("Content-Length", contentLength);
。OutOfMemoryException
每当您同时发送大型POST请求(例如,上传文件)时,这可能会导致。为避免这种情况,您想设置HttpURLConnection#setFixedLengthStreamingMode()
。
httpConnection.setFixedLengthStreamingMode(contentLength);
但是,如果确实事先不知道内容长度,则可以通过设置HttpURLConnection#setChunkedStreamingMode()
相应的值来使用分块流模式。这将设置HTTP Transfer-Encoding
标头,以chunked
强制将请求正文以块的形式发送。以下示例将以1KB的块发送正文。
httpConnection.setChunkedStreamingMode(1024);
请求可能会返回意外响应,而在真正的Web浏览器中却可以正常工作。服务器端可能正在根据User-Agent
请求标头阻止请求。URLConnection
默认情况下,will将其设置Java/1.6.0_19
为最后一部分显然是JRE版本的位置。您可以按如下所示覆盖它:
connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36"); // Do as if you're using Chrome 41 on Windows 7.
使用最新浏览器中的User-Agent字符串。
如果HTTP响应代码是4nn
(客户端错误)或5nn
(服务器错误),则您可能需要阅读,HttpURLConnection#getErrorStream()
以查看服务器是否发送了任何有用的错误信息。
InputStream error = ((HttpURLConnection) connection).getErrorStream();
如果HTTP响应代码为-1,则连接和响应处理出错。该HttpURLConnection
实现是在较旧的JRE中进行的,有些bug会使连接保持活动状态。您可能需要通过将http.keepAlive
system属性设置为来关闭它false
。您可以通过以下方式在应用程序的开头以编程方式执行此操作:
System.setProperty("http.keepAlive", "false");
通常,multipart/form-data
对混合的POST内容(二进制和字符数据)使用编码。编码在RFC2388中有更详细的描述。
String param = "value";
File textFile = new File("/path/to/file.txt");
File binaryFile = new File("/path/to/file.bin");
String boundary = Long.toHexString(System.currentTimeMillis()); // Just generate some unique random value.
String CRLF = "\r\n"; // Line separator required by multipart/form-data.
URLConnection connection = new URL(url).openConnection();
connection.setDoOutput(true);
connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
try (
OutputStream output = connection.getOutputStream();
PrintWriter writer = new PrintWriter(new OutputStreamWriter(output, charset), true);
) {
// Send normal param.
writer.append("--" + boundary).append(CRLF);
writer.append("Content-Disposition: form-data; name=\"param\"").append(CRLF);
writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF);
writer.append(CRLF).append(param).append(CRLF).flush();
// Send text file.
writer.append("--" + boundary).append(CRLF);
writer.append("Content-Disposition: form-data; name=\"textFile\"; filename=\"" + textFile.getName() + "\"").append(CRLF);
writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF); // Text file itself must be saved in this charset!
writer.append(CRLF).flush();
Files.copy(textFile.toPath(), output);
output.flush(); // Important before continuing with writer!
writer.append(CRLF).flush(); // CRLF is important! It indicates end of boundary.
// Send binary file.
writer.append("--" + boundary).append(CRLF);
writer.append("Content-Disposition: form-data; name=\"binaryFile\"; filename=\"" + binaryFile.getName() + "\"").append(CRLF);
writer.append("Content-Type: " + URLConnection.guessContentTypeFromName(binaryFile.getName())).append(CRLF);
writer.append("Content-Transfer-Encoding: binary").append(CRLF);
writer.append(CRLF).flush();
Files.copy(binaryFile.toPath(), output);
output.flush(); // Important before continuing with writer!
writer.append(CRLF).flush(); // CRLF is important! It indicates end of boundary.
// End of multipart/form-data.
writer.append("--" + boundary + "--").append(CRLF).flush();
}
如果另一侧是HttpServlet
,则将doPost()
调用其方法,并且将通过HttpServletRequest#getPart()
(请注意,因此不是 getParameter()
,依此类推!)来提供部件。getPart()
但是,该方法相对较新,它是在Servlet 3.0中引入的(Glassfish 3,Tomcat 7等)。在Servlet 3.0之前,您最好的选择是使用Apache Commons FileUpload解析multipart/form-data
请求。另请参见此答案,以获取FileUpload和Servelt 3.0方法的示例。
有时您需要连接HTTPS URL,这可能是因为您正在编写网络抓取工具。在这种情况下,您可能会遇到javax.net.ssl.SSLException: Not trusted server certificate
在某些HTTPS站点上没有保持其SSL证书最新的情况,java.security.cert.CertificateException: No subject alternative DNS name matching [hostname] found
或者javax.net.ssl.SSLProtocolException: handshake alert: unrecognized_name
在某些配置错误的HTTPS站点上遇到或。
static
您的Web scraper类中的以下一次性运行初始化程序应使HttpsURLConnection
那些HTTPS站点更为宽大,因此不再抛出这些异常。
static {
TrustManager[] trustAllCertificates = new TrustManager[] {
new X509TrustManager() {
@Override
public X509Certificate[] getAcceptedIssuers() {
return null; // Not relevant.
}
@Override
public void checkClientTrusted(X509Certificate[] certs, String authType) {
// Do nothing. Just allow them all.
}
@Override
public void checkServerTrusted(X509Certificate[] certs, String authType) {
// Do nothing. Just allow them all.
}
}
};
HostnameVerifier trustAllHostnames = new HostnameVerifier() {
@Override
public boolean verify(String hostname, SSLSession session) {
return true; // Just allow them all.
}
};
try {
System.setProperty("jsse.enableSNIExtension", "false");
SSLContext sc = SSLContext.getInstance("SSL");
sc.init(null, trustAllCertificates, new SecureRandom());
HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());
HttpsURLConnection.setDefaultHostnameVerifier(trustAllHostnames);
}
catch (GeneralSecurityException e) {
throw new ExceptionInInitializerError(e);
}
}
在Apache的HttpClient的HttpComponents是多少这一切更方便:)
如果您想要的只是从HTML解析和提取数据,那么最好使用Jsoup这样的HTML解析器
Ask Question
右上方的按钮。
--
部分不是边界本身的一部分。这只是一个分隔符字符串。我已回滚您的无效修改。
HttpClient
,这HttpURLConnection
很残酷。android-developers.blogspot.in/2011/09/...
当使用HTTP时,引用HttpURLConnection
而不是基类几乎总是有用的URLConnection
(因为URLConnection
当您请求URLConnection.openConnection()
HTTP URL时,这是一个抽象类,无论如何您都会得到它)。
然后,您可以不用依赖于URLConnection#setDoOutput(true)
将请求方法隐式设置为POST,而可以做httpURLConnection.setRequestMethod("POST")
一些可能更自然的事情(并且还可以指定其他请求方法,例如PUT,DELETE,...)。
它还提供了有用的HTTP常量,因此您可以执行以下操作:
int responseCode = httpURLConnection.getResponseCode();
if (responseCode == HttpURLConnection.HTTP_OK) {
setDoOutput()
为,true
否则会引发异常(即使您是setRequestMethod("POST")
)。明确说明:设置URLConnection#setDoOutput(true)
为true
隐式将请求方法设置httpURLConnection.setRequestMethod("POST")
为POST ,但设置为POST则没有隐式设置setDoOutput()
为true
。
受这个问题以及关于SO的其他问题的启发,我创建了一个最小的开源basic-http-client,体现了此处找到的大多数技术。
google-http-java-client也是一个很好的开源资源。
我建议您看一下kevinsawicki / http-request上的代码,基本上,它上面的包装器HttpUrlConnection
提供了更简单的API,以防万一您现在只想发出请求,或者您可以看一下源代码( (不是太大)以了解如何处理连接。
示例:GET
使用内容类型application/json
和一些查询参数发出请求:
// GET http://google.com?q=baseball%20gloves&size=100
String response = HttpRequest.get("http://google.com", true, "q", "baseball gloves", "size", 100)
.accept("application/json")
.body();
System.out.println("Response was: " + response);
HTTP URL Hits有两个选项:GET / POST
GET请求:
HttpURLConnection.setFollowRedirects(true); // defaults to true
String url = "https://name_of_the_url";
URL request_url = new URL(url);
HttpURLConnection http_conn = (HttpURLConnection)request_url.openConnection();
http_conn.setConnectTimeout(100000);
http_conn.setReadTimeout(100000);
http_conn.setInstanceFollowRedirects(true);
System.out.println(String.valueOf(http_conn.getResponseCode()));
POST请求:
HttpURLConnection.setFollowRedirects(true); // defaults to true
String url = "https://name_of_the_url"
URL request_url = new URL(url);
HttpURLConnection http_conn = (HttpURLConnection)request_url.openConnection();
http_conn.setConnectTimeout(100000);
http_conn.setReadTimeout(100000);
http_conn.setInstanceFollowRedirects(true);
http_conn.setDoOutput(true);
PrintWriter out = new PrintWriter(http_conn.getOutputStream());
if (urlparameter != null) {
out.println(urlparameter);
}
out.close();
out = null;
System.out.println(String.valueOf(http_conn.getResponseCode()));
这个回应也给我很大的启发。
我经常在需要执行一些HTTP的项目中,并且我可能不想引入很多第三方依赖性(引入了其他依此类推,依此类推,等等)。
我开始根据一些对话来编写自己的实用程序(未完成):
package org.boon.utils;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.Map;
import static org.boon.utils.IO.read;
public class HTTP {
然后只有一堆或静态方法。
public static String get(
final String url) {
Exceptions.tryIt(() -> {
URLConnection connection;
connection = doGet(url, null, null, null);
return extractResponseString(connection);
});
return null;
}
public static String getWithHeaders(
final String url,
final Map<String, ? extends Object> headers) {
URLConnection connection;
try {
connection = doGet(url, headers, null, null);
return extractResponseString(connection);
} catch (Exception ex) {
Exceptions.handle(ex);
return null;
}
}
public static String getWithContentType(
final String url,
final Map<String, ? extends Object> headers,
String contentType) {
URLConnection connection;
try {
connection = doGet(url, headers, contentType, null);
return extractResponseString(connection);
} catch (Exception ex) {
Exceptions.handle(ex);
return null;
}
}
public static String getWithCharSet(
final String url,
final Map<String, ? extends Object> headers,
String contentType,
String charSet) {
URLConnection connection;
try {
connection = doGet(url, headers, contentType, charSet);
return extractResponseString(connection);
} catch (Exception ex) {
Exceptions.handle(ex);
return null;
}
}
然后发布...
public static String postBody(
final String url,
final String body) {
URLConnection connection;
try {
connection = doPost(url, null, "text/plain", null, body);
return extractResponseString(connection);
} catch (Exception ex) {
Exceptions.handle(ex);
return null;
}
}
public static String postBodyWithHeaders(
final String url,
final Map<String, ? extends Object> headers,
final String body) {
URLConnection connection;
try {
connection = doPost(url, headers, "text/plain", null, body);
return extractResponseString(connection);
} catch (Exception ex) {
Exceptions.handle(ex);
return null;
}
}
public static String postBodyWithContentType(
final String url,
final Map<String, ? extends Object> headers,
final String contentType,
final String body) {
URLConnection connection;
try {
connection = doPost(url, headers, contentType, null, body);
return extractResponseString(connection);
} catch (Exception ex) {
Exceptions.handle(ex);
return null;
}
}
public static String postBodyWithCharset(
final String url,
final Map<String, ? extends Object> headers,
final String contentType,
final String charSet,
final String body) {
URLConnection connection;
try {
connection = doPost(url, headers, contentType, charSet, body);
return extractResponseString(connection);
} catch (Exception ex) {
Exceptions.handle(ex);
return null;
}
}
private static URLConnection doPost(String url, Map<String, ? extends Object> headers,
String contentType, String charset, String body
) throws IOException {
URLConnection connection;/* Handle output. */
connection = new URL(url).openConnection();
connection.setDoOutput(true);
manageContentTypeHeaders(contentType, charset, connection);
manageHeaders(headers, connection);
IO.write(connection.getOutputStream(), body, IO.CHARSET);
return connection;
}
private static void manageHeaders(Map<String, ? extends Object> headers, URLConnection connection) {
if (headers != null) {
for (Map.Entry<String, ? extends Object> entry : headers.entrySet()) {
connection.setRequestProperty(entry.getKey(), entry.getValue().toString());
}
}
}
private static void manageContentTypeHeaders(String contentType, String charset, URLConnection connection) {
connection.setRequestProperty("Accept-Charset", charset == null ? IO.CHARSET : charset);
if (contentType!=null && !contentType.isEmpty()) {
connection.setRequestProperty("Content-Type", contentType);
}
}
private static URLConnection doGet(String url, Map<String, ? extends Object> headers,
String contentType, String charset) throws IOException {
URLConnection connection;/* Handle output. */
connection = new URL(url).openConnection();
manageContentTypeHeaders(contentType, charset, connection);
manageHeaders(headers, connection);
return connection;
}
private static String extractResponseString(URLConnection connection) throws IOException {
/* Handle input. */
HttpURLConnection http = (HttpURLConnection)connection;
int status = http.getResponseCode();
String charset = getCharset(connection.getHeaderField("Content-Type"));
if (status==200) {
return readResponseBody(http, charset);
} else {
return readErrorResponseBody(http, status, charset);
}
}
private static String readErrorResponseBody(HttpURLConnection http, int status, String charset) {
InputStream errorStream = http.getErrorStream();
if ( errorStream!=null ) {
String error = charset== null ? read( errorStream ) :
read( errorStream, charset );
throw new RuntimeException("STATUS CODE =" + status + "\n\n" + error);
} else {
throw new RuntimeException("STATUS CODE =" + status);
}
}
private static String readResponseBody(HttpURLConnection http, String charset) throws IOException {
if (charset != null) {
return read(http.getInputStream(), charset);
} else {
return read(http.getInputStream());
}
}
private static String getCharset(String contentType) {
if (contentType==null) {
return null;
}
String charset = null;
for (String param : contentType.replace(" ", "").split(";")) {
if (param.startsWith("charset=")) {
charset = param.split("=", 2)[1];
break;
}
}
charset = charset == null ? IO.CHARSET : charset;
return charset;
}
反正你懂这个意思....
测试如下:
static class MyHandler implements HttpHandler {
public void handle(HttpExchange t) throws IOException {
InputStream requestBody = t.getRequestBody();
String body = IO.read(requestBody);
Headers requestHeaders = t.getRequestHeaders();
body = body + "\n" + copy(requestHeaders).toString();
t.sendResponseHeaders(200, body.length());
OutputStream os = t.getResponseBody();
os.write(body.getBytes());
os.close();
}
}
@Test
public void testHappy() throws Exception {
HttpServer server = HttpServer.create(new InetSocketAddress(9212), 0);
server.createContext("/test", new MyHandler());
server.setExecutor(null); // creates a default executor
server.start();
Thread.sleep(10);
Map<String,String> headers = map("foo", "bar", "fun", "sun");
String response = HTTP.postBodyWithContentType("http://localhost:9212/test", headers, "text/plain", "hi mom");
System.out.println(response);
assertTrue(response.contains("hi mom"));
assertTrue(response.contains("Fun=[sun], Foo=[bar]"));
response = HTTP.postBodyWithCharset("http://localhost:9212/test", headers, "text/plain", "UTF-8", "hi mom");
System.out.println(response);
assertTrue(response.contains("hi mom"));
assertTrue(response.contains("Fun=[sun], Foo=[bar]"));
response = HTTP.postBodyWithHeaders("http://localhost:9212/test", headers, "hi mom");
System.out.println(response);
assertTrue(response.contains("hi mom"));
assertTrue(response.contains("Fun=[sun], Foo=[bar]"));
response = HTTP.get("http://localhost:9212/test");
System.out.println(response);
response = HTTP.getWithHeaders("http://localhost:9212/test", headers);
System.out.println(response);
assertTrue(response.contains("Fun=[sun], Foo=[bar]"));
response = HTTP.getWithContentType("http://localhost:9212/test", headers, "text/plain");
System.out.println(response);
assertTrue(response.contains("Fun=[sun], Foo=[bar]"));
response = HTTP.getWithCharSet("http://localhost:9212/test", headers, "text/plain", "UTF-8");
System.out.println(response);
assertTrue(response.contains("Fun=[sun], Foo=[bar]"));
Thread.sleep(10);
server.stop(0);
}
@Test
public void testPostBody() throws Exception {
HttpServer server = HttpServer.create(new InetSocketAddress(9220), 0);
server.createContext("/test", new MyHandler());
server.setExecutor(null); // creates a default executor
server.start();
Thread.sleep(10);
Map<String,String> headers = map("foo", "bar", "fun", "sun");
String response = HTTP.postBody("http://localhost:9220/test", "hi mom");
assertTrue(response.contains("hi mom"));
Thread.sleep(10);
server.stop(0);
}
@Test(expected = RuntimeException.class)
public void testSad() throws Exception {
HttpServer server = HttpServer.create(new InetSocketAddress(9213), 0);
server.createContext("/test", new MyHandler());
server.setExecutor(null); // creates a default executor
server.start();
Thread.sleep(10);
Map<String,String> headers = map("foo", "bar", "fun", "sun");
String response = HTTP.postBodyWithContentType("http://localhost:9213/foo", headers, "text/plain", "hi mom");
System.out.println(response);
assertTrue(response.contains("hi mom"));
assertTrue(response.contains("Fun=[sun], Foo=[bar]"));
Thread.sleep(10);
server.stop(0);
}
您可以在这里找到其余的内容:
https://github.com/RichardHightower/boon
我的目标是以一种比...更简单的方式提供人们想做的普通事情。
doPost
方法中有一个charset
用于设置请求标头的参数,但是随后使用一些硬编码的字符集写入数据IO.CHARSET
。有毛病吗
新的HTTP客户端随Java 9一起提供,但作为名为Incubator模块的一部分
jdk.incubator.httpclient
。孵化器模块是一种将非最终API交给开发人员的方法,而这些API则可以在最终版本中逐步完成或删除。
在Java 9中,您可以发送如下GET
请求:
// GET
HttpResponse response = HttpRequest
.create(new URI("http://www.stackoverflow.com"))
.headers("Foo", "foovalue", "Bar", "barvalue")
.GET()
.response();
然后,您可以检查返回的内容HttpResponse
:
int statusCode = response.statusCode();
String responseBody = response.body(HttpResponse.asString());
由于此新的HTTP客户端位于 java.httpclient
jdk.incubator.httpclient
模块,您应该在module-info.java
文件中声明此依赖项:
module com.foo.bar {
requires jdk.incubator.httpclient;
}
后来我意识到,HttpURLConnection
这篇文章将保留这一点。
根据Google博客:
Apache HTTP客户端在Eclair和Froyo上的错误更少。这是这些版本的最佳选择。对于Gingerbread来说,HttpURLConnection是最佳选择。其简单的API和较小的尺寸使其非常适合Android。
透明的压缩和响应缓存减少了网络使用,提高了速度并节省了电池。新的应用程序应该使用HttpURLConnection;这是我们将花费精力继续前进的地方。
在阅读了本文和其他一些有关流程的问题之后,我相信它将HttpURLConnection
持续更长的时间。
一些SE问题青睐HttpURLConnections
:
还有一个OkHttp,它是默认情况下有效的HTTP客户端:
- HTTP / 2支持允许对同一主机的所有请求共享一个套接字。
- 连接池可减少请求延迟(如果HTTP / 2不可用)。
- 透明的GZIP缩小了下载大小。
- 响应缓存可以完全避免网络重复请求。
首先创建一个实例OkHttpClient
:
OkHttpClient client = new OkHttpClient();
然后,准备您的GET
请求:
Request request = new Request.Builder()
.url(url)
.build();
最后,用OkHttpClient
发送来准备Request
:
Response response = client.newCall(request).execute();
有关更多详细信息,可以查阅OkHttp的文档。
您还可以JdkRequest
在jcabi-http(我是开发人员)中使用它,它可以为您完成所有这些工作,装饰HttpURLConnection,触发HTTP请求并解析响应,例如:
String html = new JdkRequest("http://www.google.com").fetch().body();
查看此博客文章以了解更多信息:http : //www.yegor256.com/2014/04/11/jcabi-http-intro.html
如果您使用的是http get,请删除此行
urlConnection.setDoOutput(true);