Using the java client to access the website is a necessary skill for programmers, and the default java package java.net supports it
package Http.client;
import java.io.InputStream;
import java.net.URL;
import java.util.Scanner;
/**
* Class description Use the net class of the official website for testing
*
* @author rfk
*/
public class JavaNet {
@SuppressWarnings("resource")
public static void main(String args[]) {
String urla = "https://www.baidu.com/";
URL myUrl = null;
try {
myUrl = new URL (urla);
InputStream input = myUrl.openStream();
Scanner scan = new Scanner(input);
scan.useDelimiter("\n");
while (scan.hasNext()) {
String str = scan.next();
System.out.println(str);
}
} catch (Exception e) {
e.printStackTrace ();
}
}
}
The method of get request and address splicing is used here. If you use post request, you need to set the header.
package Http.client;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
/**
* class description
*
* @author rfk
*/
public class TestHttpUrl {
public static void main(String[] args) {
URL url = null;
try {
url = new URL("http://localhost:9180/" + "abcde");
} catch (MalformedURLException e) {
e.printStackTrace ();
}
HttpURLConnection connection = null;
try {
connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setDoInput(true);
connection.setRequestMethod("POST");
connection.setUseCaches(false);
connection.setInstanceFollowRedirects(true);
connection.setRequestProperty("Content-Type", "application/json");
connection.connect();
DataOutputStream out = new DataOutputStream(connection.getOutputStream());
String str = "Transmitted data";
out.writeBytes(str);
out.flush();
out.close();
} catch (IOException e) {
e.printStackTrace ();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
StringBuffer buffer = new StringBuffer("");
String lines;
while ((lines = reader.readLine()) != null) {
buffer.append(lines);
reader.close();
connection.disconnect();
}
} catch (IOException e) {
e.printStackTrace ();
}
}
}
It is very troublesome to observe the code, so refer to httpclient
package Http.client;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.CloseableHttpResponse;
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;
/**
* class description
*
* @author rfk
*/
public class TestHttpClientGet {
public static void main(String[] args) {
// If String url="www.baidu.com"; there will be an error
String url = "http://www.baidu.cn/";
CloseableHttpClient client = HttpClients.createDefault();
HttpGet httpGet = new HttpGet(url);
CloseableHttpResponse response = null;
try {
response = client.execute(httpGet);
int code = response.getStatusLine().getStatusCode();
if (code == 200) {
String str = EntityUtils.toString(response.getEntity());
System.err.println(str);
File fi = new File("/Users/sona/Desktop/a.txt");
if (fi.getParent() != null) {
if (!fi.exists())
fi.createNewFile();
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(fi));
out.write(str.getBytes());
out.flush();
out.close();
} else {
try {
throw new Exception();
} catch (Exception e) {
e.printStackTrace ();
}
}
}
} catch (ClientProtocolException e) {
e.printStackTrace ();
} catch (IOException e) {
e.printStackTrace ();
} finally {
try {
response.close();
client.close();
} catch (IOException e) {
e.printStackTrace ();
}
}
}
}
If it is a post request, the code is as follows
package Http.client;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.NameValuePair;
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.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
/**
* class description
*
* @author rfk
*/
public class TestHttpClientPost {
public final static String url = "http://www.baidu.com";
// The address to be accessed
public static void main(String[] args) throws Exception {
CloseableHttpClient httpClient = HttpClients.createDefault();
// Create a client for HTTP access
HttpPost httpPost = new HttpPost(url);
// Now about to send a post request NameValuePair is an interface
List<NameValuePair> allParams = new ArrayList<NameValuePair>();
// All request parameters need to be processed in a package
// public class BasicNameValuePair implements NameValuePair
allParams.add(new BasicNameValuePair("msg", "Hello world!"));
// Append the passed parameters
allParams.add(new BasicNameValuePair("mid", "helloworld"));
// Append the passed parameters
// Since Chinese is now passed, it is necessary to control encoding for Chinese
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(allParams, "UTF-8");// Set Baini Ma
httpPost.setEntity(entity);
// Bind the data to be sent with the POST request object
CloseableHttpResponse response = httpClient.execute(httpPost); // 发送GET请求
System.out.println(response.getEntity());
int status = response.getStatusLine().getStatusCode();
if (status >= 200 && status < 300) {
InputStream input = response.getEntity().getContent();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] data = new byte[1024];
int len = 0;
while ((len = input.read(data)) != -1) {
bos.write(data, 0, len);
}
System.out.println(new String(bos.toByteArray()));
} else {
throw new ClientProtocolException("Unexpected response status: " + status);
}
}
}
If you need to upload files in the java client section
package Http.client;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.InputStream;
import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.entity.mime.content.StringBody;
import org.apache.http.impl.client.HttpClients;
public class HttpClientUploadDemo {
public static void main(String[] args) throws Exception {
// file to upload
File file = new File("D:" + File.separator + "dog.jpg");
//path
String url = "http://www.baidu.com";
// Create an HttpClient action class
HttpClient httpClient = HttpClients.createDefault();
//create post
HttpPost httpPost = new HttpPost(url);
// If you want to upload files, you must use "multipart/form-data" to set
MultipartEntityBuilder builder = MultipartEntityBuilder.create();
builder.addPart("photo", new FileBody(file, ContentType.create("image/jpeg")));
builder.addPart("msg", new StringBody("世界，你好", ContentType.create("text/plain", Consts.UTF_8)));
HttpEntity entity = builder.build(); // Define upload entity class
httpPost.setEntity(entity);
HttpResponse response = httpClient.execute(httpPost); // Send post request
System.out.println(response.getEntity());
System.out.println(response.getStatusLine().getStatusCode());
InputStream input = response.getEntity().getContent();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] data = new byte[1024];
int len = 0;
while ((len = input.read(data)) != -1) {
bos.write(data, 0, len);
}
System.out.println(new String(bos.toByteArray()));
}
}
The following code tools are reproduced from http://blog.csdn.net/u012878380/article/details/54907246
package Http.client;
import java.io.IOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
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.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
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;
/**
* class description
*
* @author rfk
*/
public class HttpClientUtil {
public static String doGet(String url, Map<String, String> param) {
// Create Httpclient object
CloseableHttpClient httpclient = HttpClients.createDefault();
String resultString = "";
CloseableHttpResponse response = null;
try {
// Jian Jian uri
URIBuilder builder = new URIBuilder(url);
if (param != null) {
for (String key : param.keySet()) {
builder.addParameter(key, param.get(key));
}
}
URI uri = builder.build ();
// Create http GET request
HttpGet httpGet = new HttpGet(uri);
// execute the request
response = httpclient.execute(httpGet);
// Determine if the return status is 200
if (response.getStatusLine().getStatusCode() == 200) {
resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
}
} catch (Exception e) {
e.printStackTrace ();
} finally {
try {
if (response != null) {
response.close();
}
httpclient.close();
} catch (IOException e) {
e.printStackTrace ();
}
}
return resultString;
}
public static String doGet(String url) {
return doGet(url, null);
}
public static String doPost(String url, Map<String, String> param) {
// Create Httpclient object
CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = null;
String resultString = "";
try {
// Create Http Post request
HttpPost httpPost = new HttpPost(url);
// create parameter list
if (param != null) {
List<NameValuePair> paramList = new ArrayList<>();
for (String key : param.keySet()) {
paramList.add(new BasicNameValuePair(key, param.get(key)));
}
// mock form
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList, "utf-8");
httpPost.setEntity(entity);
}
// execute the http request
response = httpClient.execute(httpPost);
resultString = EntityUtils.toString(response.getEntity(), "utf-8");
} catch (Exception e) {
e.printStackTrace ();
} finally {
try {
response.close();
} catch (IOException e) {
e.printStackTrace ();
}
}
return resultString;
}
public static String doPost(String url) {
return doPost(url, null);
}
public static String doPostJson(String url, String json) {
// Create Httpclient object
CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = null;
String resultString = "";
try {
// Create Http Post request
HttpPost httpPost = new HttpPost(url);
// create request content
StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
httpPost.setEntity(entity);
// execute the http request
response = httpClient.execute(httpPost);
resultString = EntityUtils.toString(response.getEntity(), "utf-8");
} catch (Exception e) {
e.printStackTrace ();
} finally {
try {
response.close();
} catch (IOException e) {
e.printStackTrace ();
}
}
return resultString;
}
}
Upload the code to github: https://github.com/sona0402/url-httpclient.git