This example shows you how to get the Http response header values in Java.
1. Standard JDK example.
URL obj = new URL("https://mkyong.com");
URLConnection conn = obj.openConnection();
//get all headers
Map<String, List<String>> map = conn.getHeaderFields();
for (Map.Entry<String, List<String>> entry : map.entrySet()) {
System.out.println("Key : " + entry.getKey() +
" ,Value : " + entry.getValue());
}
//get header by 'key'
String server = conn.getHeaderField("Server");
2. Apache HttpClient example.
HttpClient client = HttpClientBuilder.create().build();
HttpGet request = new HttpGet("https://mkyong.com");
HttpResponse response = client.execute(request);
//get all headers
Header[] headers = response.getAllHeaders();
for (Header header : headers) {
System.out.println("Key : " + header.getName()
+ " ,Value : " + header.getValue());
}
//get header by 'key'
String server = response.getFirstHeader("Server").getValue();
1. URLConnection Example
See a full example to get response headers value via URLConnection.
ResponseHeaderUtil.java
package com.mkyong;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;
public class ResponseHeaderUtil {
public static void main(String[] args) {
try {
URL obj = new URL("https://mkyong.com");
URLConnection conn = obj.openConnection();
Map<String, List<String>> map = conn.getHeaderFields();
System.out.println("Printing Response Header...\n");
for (Map.Entry<String, List<String>> entry : map.entrySet()) {
System.out.println("Key : " + entry.getKey()
+ " ,Value : " + entry.getValue());
}
System.out.println("\nGet Response Header By Key ...\n");
String server = conn.getHeaderField("Server");
if (server == null) {
System.out.println("Key 'Server' is not found!");
} else {
System.out.println("Server - " + server);
}
System.out.println("\n Done");
} catch (Exception e) {
e.printStackTrace();
}
}
}
Output
Printing Response Header...
Key : null ,Value : [HTTP/1.1 200 OK]
Key : ETag ,Value : ["713cd-9b82-4dd6d789447c0"]
Key : Content-Length ,Value : [39810]
Key : Expires ,Value : [Fri, 24 May 2013 03:22:31 GMT]
Key : Last-Modified ,Value : [Fri, 24 May 2013 02:22:31 GMT]
Key : Connection ,Value : [Keep-Alive]
Key : X-Powered-By ,Value : [W3 Total Cache/0.9.2.9]
Key : Server ,Value : [Apache/2.2.22 (Unix) mod_ssl/2.2.22 OpenSSL/1.0.0-fips mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635]
Key : Pragma ,Value : [public]
Key : Cache-Control ,Value : [public]
Key : Date ,Value : [Fri, 24 May 2013 02:22:37 GMT]
Key : Vary ,Value : [Accept-Encoding,Cookie]
Key : Keep-Alive ,Value : [timeout=2, max=100]
Key : Content-Type ,Value : [text/html]
Key : Accept-Ranges ,Value : [bytes]
Get Response Header By Key ...
Server - Apache/2.2.22 (Unix) mod_ssl/2.2.22 OpenSSL/1.0.0-fips mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635
Done
2. Apache HttpClient Example
This is an equivalent example, but using Apache HttpClient.
ResponseHeaderUtil.java
package com.mkyong;
import org.apache.http.Header;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClientBuilder;
public class ResponseHeaderUtil {
public static void main(String[] args) {
try {
HttpClient client = HttpClientBuilder.create().build();
HttpGet request = new HttpGet("https://mkyong.com");
HttpResponse response = client.execute(request);
System.out.println("Printing Response Header...\n");
Header[] headers = response.getAllHeaders();
for (Header header : headers) {
System.out.println("Key : " + header.getName()
+ " ,Value : " + header.getValue());
}
System.out.println("\nGet Response Header By Key ...\n");
String server = response.getFirstHeader("Server").getValue();
if (server == null) {
System.out.println("Key 'Server' is not found!");
} else {
System.out.println("Server - " + server);
}
System.out.println("\n Done");
} catch (Exception e) {
e.printStackTrace();
}
}
}
What if I want to get Retry-After HTTP header from the 429 response? Because the URLConnection actually throws an IOException on this HTTP response. How do you get it from the catch block?
how to capture the response time, for example if i hit an end point…Postman we will get Time: 99 ms, can we do it same as in java please show some light on it.
Hello and thanks for the post! Any idea how to get the network element status codes? I dont mean th url response, i mean the responses of the page elements, thanks!
Hi
How to parse pagination rest api calls in java
Thanks
Hi!
Firstly, thanks for your articles! they’ve been very useful for me.
I have a doubt; how do you access the fields in the HttpResponse body instead of the headers?
My HttpResponse is like this:
{“APIKey”:”cf5f037d-8ac5-481f-b629″,”StatusCode”:0,”StatusMessage”:”You have been successfully logged in.”}
and I need to take the APIKey value from it. is there a way to do this?
thanks!
create a json object containing all those (3) properties,
retrieve the value with respose.readEntity(YourCustomJsonObject.class).getApiKey()
Recommended PHP based online http header checker
http://freeonlinetools24.com/status
NullPointerException is possible: String server = response.getFirstHeader(“Server”).getValue();
try to access http://www.sam.gov -> DATA ACCESS page via the java urlconnection, the response status is right, but the response content was not.
any idea?
the code is as following:
URL url1 = new URL(“https://www.sam.gov/”);
HttpsURLConnection conn = (HttpsURLConnection) url1.openConnection();
String cookie =””;
String cookstr =””;
String postaction=””;
String url = “https://www.sam.gov”;
String idstr = “”;
String idvalStr =””;
String formid = “”;
int lc =6 ;
conn.setRequestProperty(“Cookie”, cookie);
conn.connect();
BufferedReader inn = new BufferedReader(
new InputStreamReader(conn.getInputStream()));
String inputLine1;
StringBuffer response1 = new StringBuffer();
while ((inputLine1 = inn.readLine()) != null ) {
if (inputLine1.indexOf(“_viewRoot:extractsForm”) >0 && inputLine1.indexOf(“action=”) >0 ) {
System.out.println(inputLine1);
postaction = url + inputLine1.substring(inputLine1.indexOf(“action=”) + 8 , inputLine1.indexOf(“type=action”) + 12 ) ;
postaction = postaction.replaceAll(“amp;”, “”);
System.out.println(“postURL ” + postaction);
lc–;
continue;
}
if (lc == 5 ) {
if (inputLine1.indexOf(“input type=”) >0 && inputLine1.indexOf(“value=”) >0 ) {
idstr = inputLine1.substring(inputLine1.indexOf(“name=”) + 6 , inputLine1.indexOf(“extractsForm”) + 12 );
idvalStr = inputLine1.substring(inputLine1.indexOf(“value=”) + 7 , inputLine1.indexOf(“/>”) – 2 ) ;
idstr = URLEncoder.encode(idstr, “UTF-8”);
idvalStr = URLEncoder.encode(idvalStr, “UTF-8”);
formid = URLEncoder.encode(idstr + “:extracts”, “UTF-8”);
System.out.println(“idstr ” + idstr);
System.out.println(“idvalStr ” + idvalStr ) ;
}
lc–;
}
}
inn.close();
String headerName = null;
List cookies = conn.getHeaderFields().get(“Set-Cookie”);
for (int i = 1; (headerName = conn.getHeaderFieldKey(i)) != null; i++) {
if (headerName.equals(“Set-Cookie”)) {
cookstr = conn.getHeaderField(i);
if (conn.getHeaderField(i).startsWith(“JSESSIONID”)) {
cookie = conn.getHeaderField(i).substring(0, conn.getHeaderField(i).indexOf(“;”)).trim();
}
}
}
System.out.println(“cookie ” + cookstr);
URL obj = new URL( postaction );
HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();
con.setDoOutput(true);
con.setDoInput(true);
con.setUseCaches(false);
// con.setRequestProperty(“Content-Type”, “text/plain; charset=UTF-8”);
con.setRequestProperty(“Accept”, “application/json”);
con.setRequestProperty(“Content-Type”, “application/json; charset=UTF-8”);
con.setRequestMethod(“POST”);
JSONObject jsonParam = new JSONObject();
jsonParam.put(idstr, idvalStr);
jsonParam.put(“javax.faces.ViewState”, “j_id1″);
jsonParam.put(formid, formid);
OutputStreamWriter out = new OutputStreamWriter(con.getOutputStream(),”UTF-8”);
out.write(jsonParam.toString());
out.close();
int responseCode = con.getResponseCode();
Map<String, List> map = conn.getHeaderFields();
for (Map.Entry<String, List> entry : map.entrySet()) {
System.out.println(“Key : ” + entry.getKey() +
” ,Value : ” + entry.getValue());
}
System.out.println(“nSending ‘POST’ request to URL : ” + postaction.replace(“&”,”&”));
System.out.println(“Post parameters : ” + jsonParam.toString());
// System.out.println(“content-length :” + urlParameters.getBytes(“UTF-8”).length);
System.out.println(“Response Code : ” + responseCode);
System.out.println(“Resp Message:”+ con.getResponseMessage());
BufferedReader in = new BufferedReader(
new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer response = new StringBuffer();
// con.getOutputStream()
while ((inputLine = in.readLine()) != null) {
if (inputLine.indexOf(“.ZIP”) >0 ) {
System.out.println(inputLine);
}
}
in.close();
//print result
System.out.println(response.toString());
}
why my HttpClientBuilder is not recognized??
I’ve added the dependency. Just the HttpClientBuilder is not recognized.. :/
this is really great and useful to me in servlet and android also ..
Hey, do you know why it doesn’t show the last-modified value for php files?
thanx very much. I’m URLConnection and I dont know how to pass string data along for the file – until I read this tutorial
Thank you very much for your tutorials. A question regarding ResponseHeaderUtil.java
I used the statement
String fileLength = conn.getHeaderField(“Content-Length”);
in an Android app and it blocked the app. There were no errors listed. The application just did not continue to do what it had to do (to download a file and show the progress in a progress bar.) I f get the length of the file with
fileLength = connection.getContentLength();
then the application works ok. Any idea about what could have happened?
I tried the Apache version and it works! I would still like to know why the Java version does not work.
Hi, I just wanted to say, “Thank you.” Your posts have helped me many times.
I agree