All about Ron McLeod

Reduce Stream to Contain Last Element Only

Piet Souris wrote:First thought: intstream iterate from size ...

With my case, I don't know the size in-advance, and to discover it, I would need to fully consume the stream.

2 hours ago

Reduce Stream to Contain Last Element Only

I want to be able to transform a stream with zero or more elements into a stream with zero or one elements, where the element is the last element from the original stream.

The code below does work, but I wondering if there might be a better way where I don't need to process each element one-by-one.

3 hours ago

Lambdas and Streams

Tomcat server timeout settings not working as expected.

Rajkamal Pillai wrote:My default session timeout value is set to 30 in web.xml, so -
<session-timeout>30</session-timeout>
I understand that this is applicable across all user sessions.

Yes - that setting will cause sessions to timeout after 30 minutes of inactivity (unless overridden on a per-session basis using HttpSession#setMaxInactiveInterval after the session has been created).

Rajkamal Pillai wrote:... my issue is that Users are logged off after (the default) 30 seconds.
session.setMaxInactiveInterval(300)
Does not have any effect at all.

How did you determine this? In this post I found that HttpSession#setMaxInactiveInterval works as-expected. I provided the code that I used to prove that it was working as well as test results. You should be able to use this same code in your environment to test as well.

Rajkamal Pillai wrote:My question is about how to modify the timeout interval dynamically, other than by making changes to web.xml. What worries me is my suggested solution should not cause performance and/or usability side effects.

I'm not really sure what kinds of performance/usabilities issues you might be thinking of. Can you give some examples?

Rajkamal Pillai wrote:I am on Tomcat 9.0.76
Can you kindly advice what version I should look to upgrade to?

I don't think it matters. I used 9.0.73 to test with because I already had the docker image downloaded.

The title of this thread is: Tomcat server timeout settings not working as expected.. If you can share some details when/how you are overriding the configured default timeout period, and provide some evidence that it is not working properly, then we can probably help more.

5 days ago

Tomcat

How to fix HttpsURLConnection POST XML request?

I agree with Tim that this looks like a server-side problem.

I ran basically your same code against httpbin.org and there were no issues.

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import javax.net.ssl.HttpsURLConnection;
import org.junit.jupiter.api.Test;
public class HttpTest {
   final String xml = """
           <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
           <a:ExampleRequest
                   xmlns:a="http://test/schema/1.0/example">
           <ExampleRequestDetails>
           <Id>1</Id>
           <ClientId>9999</ClientId>
           </ExampleRequestDetails>
           </a:ExampleRequest>
               """;
   final String endpointUrl = "https://httpbin.org/post";
   @Test
   public void make_http_connection_with_xml_payload() throws IOException {
       URL url = new URL(endpointUrl);
       HttpsURLConnection connection = (HttpsURLConnection) url.openConnection();
       connection.setRequestMethod("POST");
       connection.addRequestProperty("Accept-Charset", "UTF-8");
       connection.setRequestProperty("Content-Type", "application/xml; charset=utf-8");
       connection.setDoInput(true);
       connection.setDoOutput(true);
       connection.getOutputStream().write(xml.getBytes(StandardCharsets.UTF_8));
       InputStream is = connection.getInputStream();
       int responseCode = connection.getResponseCode();
       System.out.println("response code: " + responseCode);
       String responseResult = connection.getResponseMessage();
       System.out.println("response result: " + responseResult);
       byte[] returnedContent = is.readAllBytes();
       System.out.println("returned content:\n" + new String(returnedContent));
   }
}

1 week ago

Java in General

Tomcat server timeout settings not working as expected.

Rajkamal Pillai wrote:The issue I face is that the value set through setMaxInactiveInterval() does not have appear to have much effect.
Remember reading that the timeout value will be defaulted to the value in web.xml (by a Tomcat process?).

Am I correct and is there any way around this?

I'm really sure where you are at now - after doing some testing, I am going to reply your original question.

Yes, HttpSession#setMaxInactiveInterval does change affect the timeout period for an inactive session. Running Tomcat version 9.0.73.0, I observed that the the session will timeout (and be destroyed) sometime after the specified interval. It appears like with the version of Tomcat that I was running, that a timeout check is performed every 60 seconds, so the actual time when the session is declared invalid can be up to 60 seconds after what you might expect.

Test setup:

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
@WebListener
public class SessionListener implements HttpSessionListener {
   final static boolean SET_INTERVAL = true;
   final static int NEW_INTERVAL_SECONDS = 120;
   public void sessionCreated(final HttpSessionEvent event) {
       var session = event.getSession();
       session.setAttribute("StartTs", System.currentTimeMillis());
       if (SET_INTERVAL) {
           session.setMaxInactiveInterval(NEW_INTERVAL_SECONDS);
       }
       System.out.printf("SessionListener.sessionCreated() %s%n", getMessage(session));
   }
   public void sessionDestroyed(final HttpSessionEvent event) {
       var session = event.getSession();
       System.out.printf("SessionListener.sessionDestroyed() %s%n", getMessage(session));
       long startTs = (long) session.getAttribute("StartTs");
       var lifetimeMillis = System.currentTimeMillis() - startTs;
       System.out.printf("SessionListener.sessionDestroyed() session lifetime: %s%n",
               lifetimeMillis /1000);
   }
   String getMessage(HttpSession session) {
       var now = millisToPrintableTime(System.currentTimeMillis());
       var sessionId = session.getId();
       var creationTime = millisToPrintableTime(session.getCreationTime());
       var lastAccessedTime = millisToPrintableTime(session.getLastAccessedTime());
       var maxInactiveInterval = session.getMaxInactiveInterval();
       return String.format("now: %s, id: %s, cr: %s, la: %s, mii: %s",
               now, sessionId, creationTime, lastAccessedTime, maxInactiveInterval);
   }
   String millisToPrintableTime(long millis) {
       return LocalDateTime.ofInstant(Instant.ofEpochMilli(millis), ZoneId.systemDefault())
               .toLocalTime().toString();
   }
}

Max inactive interval not setMax inactive interval set to 60 (notice how all sessions expire at 55 second mark)Max inactive interval set to 60 (session activity after 21 seconds; created and last accessed different)Max inactive interval set to 120

1 week ago

Tomcat

Code Reviews

bonkersworld.net/img/2011-09-18_code_reviews.png

1 week ago

Meaningless Drivel

why does the compiler complain about this ternary operator: "not a statement"?

Your example will not compile because forEach expects to operate on a Consumer, and a Consumer cannot return a value.

If you wrapped it with something like System.out.println like Liutauras showed before it will also fail to compile because variables in a lambda expression need to be effectively final, and positives, zeroes, and negatives are not.

1 week ago

Java in General

Tomcat server timeout settings not working as expected.

Rajkamal Pillai wrote:The issue I face is that the User is not logged off after the timeout duration.

You should be able to get notifications of expiring sessions by registering a HttpSessionListener. It will be called just after a session has been created (sessionCreated()), and just before a session is to be invalidated (sessionDestroyed()).

2 weeks ago

Tomcat

Saving a jpg image to derby Blob

Bill - what version of Java are you working with?

2 weeks ago

JDBC and Relational Databases

Saving a jpg image to derby Blob

I don't know about the Swing side of things, but you can take a look at the saveImageToDatabase and getImageFromDatabaseAsByteArray methods for examples to put and get images with the database. I don't think you were far off, but you took a wrong turn with ObjectOutputStream.

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import org.junit.jupiter.api.Test;
public class BlobTest {
   static final String TABLE_DEF = """
           CREATE TABLE images (
               name VARCHAR(50),
               image BLOB
           )
           """;
   static final String FILE_PATH_STR = "C:/Users/Ron/Downloads/timer.png";
   static final String IMAGE_SAVE_NAME = "timer";
   Connection conn;
   @Test
   void save_image_to_database() throws SQLException, IOException {
       createConnection();
       createTable();
       var imagePath = Paths.get(FILE_PATH_STR);
       saveImageToDatabase(IMAGE_SAVE_NAME, imagePath);
       var image = getImageFromDatabaseAsByteArray(IMAGE_SAVE_NAME);
       System.out.println("Image size: " + image.length);
   }
   void createConnection() throws SQLException {
       System.out.println("Creating connection to database ...");
       var dbUrl = "jdbc:derby:memory:blobtest;create=true";
       conn = DriverManager.getConnection(dbUrl);
   }
   void createTable() throws SQLException {
       System.out.println("Creating table to store images ...");
       var stmt = conn.createStatement();
       stmt.executeUpdate(TABLE_DEF);
   }
   void saveImageToDatabase(String name, Path imagePath) throws SQLException, IOException {
       System.out.println("Saving image to database ...");
       var sql = "INSERT INTO images (name, image) VALUES (?, ?)";
       var pstmt = conn.prepareStatement(sql);
       pstmt.setString(1, name);
       var is = Files.newInputStream(imagePath);
       pstmt.setBlob(2, is);
       var count = pstmt.executeUpdate();
       var msg = count != 0 ? "Image saved" : "Failed to save image";
       System.out.println(msg);
   }
   byte[] getImageFromDatabaseAsByteArray(String name) throws SQLException {
       System.out.println("Retrieving image from database ...");
       var sql = "SELECT image FROM images WHERE name = ?";
       var pstmt = conn.prepareStatement(sql);
       pstmt.setString(1, name);
       var rs = pstmt.executeQuery();
       var found = rs.next();
       var msg = found ? "Image found" : "Image not found";
       System.out.println(msg);
       if (found) {
           return rs.getBytes(1);
       }
       return new byte[0];
   }
}

3 weeks ago

Java in General

Head First Java

https://oreil.ly/hfJava_3e_examples and https://resources.oreilly.com/examples/0636920034452 will both take you to the same repository.

kevin Abel wrote:When I look at the chapter information it shows changes to the code, but not the code in the book.

It seems like you are clicking on the wrong link in the repository view. Try clicking in the link in the Name column rather than the Last Commit column.

For example - at: https://resources.oreilly.com/examples/0636920034452/-/tree/main/src/main/java

Clicking on ch12 will take you to:

And then clicking on LimitWithStream.java will take you to:

3 weeks ago

Beginning Java

Head First Java

kevin Abel wrote:I cannot find the post on the forum even after searching a while ...

This one?: Head First Java - Where is the code from the book?

3 weeks ago

Beginning Java

switching to base64 from pdf

Jack Tauson wrote:What I'm trying to do is to send the base64 encoded string to the web browser ...

Why do you want to do that? Normally you would set the Content-Type to application/pdf, and then stream the binary content of the PDF document to the browser without any transformation.

A browser like Chrome is able to render the document directly; other browsers may launch an application such as Acrobat to perform the rendering.

4 weeks ago

Java in General

Ron McLeod

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