Errong Leng

Automate Form Filling in PDFs Using iText 5 Library in Java

By Errong Leng – 23 Oct 2023 – View online →

Have you ever needed to automatically fill out PDF forms with preset data using a Java application? In this post, we'll explore how to achieve this using the iText 5 library. iText is a popular Java library for creating and manipulating PDF documents, including form filling. We'll walk you through the steps to load an existing PDF form, access form fields, set values, and even flatten the form to make it read-only. Let's get started.

Step 1: Add iText 5 Library

Before we begin, ensure that you have the iText 5 library added to your Java project. You can download the iText 5 JAR files from the official website or use dependency management tools like Maven or Gradle.

Step 2: Load the PDF Form

Load the existing PDF form that you want to fill. You can do this using the PdfReader class in iText:

PdfReader reader = new PdfReader("path/to/your/form.pdf");  PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("path/to/output.pdf"));

Step 3: Access Form Fields

To access form fields in the PDF, you can use the AcroFields class. Set values in the form fields using the setField method:

AcroFields form = stamper.getAcroFields();  form.setField("FieldName1", "Value1");  form.setField("FieldName2", "Value2");  // Set values for other form fields as needed

Replace "FieldName1", "FieldName2", and "Value1", "Value2" with the actual field names and values you want to set.

Step 4: Flatten the Form (Optional)

If you want to make the form read-only after filling it, you can use the setFormFlattening(true) method on the PdfStamper object:

stamper.setFormFlattening(true);

Step 5: Close and Save the PDF

After filling the form fields, close the PdfStamper and save the PDF:

stamper.close();

Your filled PDF will be saved as specified in the output path.

Here's a complete example:

import com.itextpdf.text.pdf.PdfReader;  import com.itextpdf.text.pdf.PdfStamper;  import com.itextpdf.text.pdf.AcroFields;    import java.io.FileOutputStream;    public class PdfFormFiller {      public static void main(String[] args) {          try {              PdfReader reader = new PdfReader("path/to/your/form.pdf");              PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("path/to/output.pdf"));                AcroFields form = stamper.getAcroFields();              form.setField("FieldName1", "Value1");              form.setField("FieldName2", "Value2");              // Set values for other form fields as needed                stamper.setFormFlattening(true);                stamper.close();          } catch (Exception e) {              e.printStackTrace();          }      }  }

This process allows you to automate form filling in PDFs, making it convenient for applications that require bulk data entry or report generation. Just replace file paths and field names/values as needed, and you're ready to go!

Efficient File Transfer: Pushing and Pulling Files Between a Spring Boot App and an sFTP Server

Post, Code and Quiet Time.

Efficient File Transfer: Pushing and Pulling Files Between a Spring Boot App and an sFTP Server

By Errong Leng – 23 Oct 2023 – View online →

Photo by Marc Kleen / Unsplash

Are you a developer looking to seamlessly exchange files between your Spring Boot application and an sFTP server? Whether it's pushing files from your app to the server or pulling files from the server to your app, this post will guide you through the process. In this tutorial, we'll cover the steps for both operations to make your file transfers smooth and reliable.

Pushing Files from Spring Boot to sFTP Server

Dependency Setup: First, make sure your Spring Boot project is equipped with the necessary dependencies to interact with an sFTP server. You can add the spring-integration-sftp library to your project.
Configure sFTP Connection: Create a configuration file to set up the sFTP connection parameters, including the host, port, username, and password.
Develop the File Push Logic: Write the Java code to handle file push operations. You can use Spring Integration to create a flow that monitors a local directory for files to be pushed to the sFTP server.
Error Handling: Implement error handling mechanisms to deal with potential issues during the file transfer process. This ensures the reliability of your file transfer operations.
Testing: Thoroughly test the file push functionality to ensure that files are transferred successfully to the sFTP server.

Pulling Files from sFTP Server to Spring Boot

Dependency Setup: Similar to the file push operation, ensure you have the necessary dependencies to interact with the sFTP server.
Configure sFTP Connection: Create a configuration file with the sFTP connection details, just as you did for the file push operation.
Develop the File Pull Logic: Write Java code that monitors the sFTP server for files and pulls them into your Spring Boot application. Again, Spring Integration can be used for this purpose.
Error Handling: Implement error handling to manage issues that may occur during the file retrieval process.
Testing: Rigorously test the file pull functionality to ensure that files are pulled successfully from the sFTP server and stored in your Spring Boot app.

Setting Up a Free sFTP Server

For those looking to get started with sFTP, you can set up a free sFTP server for your development needs. Here are a couple of popular options:

FileZilla Server: FileZilla is a widely used open-source FTP server that also supports sFTP. You can set up FileZilla Server on your local machine or on a dedicated server. Detailed installation and configuration instructions can be found here.
OpenSSH: If you're working on a Unix-based system, you can use OpenSSH as your sFTP server. Most Linux distributions come with OpenSSH pre-installed. You can configure it for sFTP by following instructions specific to your OS.

Code in Java

Below is a Java code example that demonstrates how to set up an sFTP connection using the JSch library, connect via a username and public key authentication, and perform sFTP operations such as pushing a file, pulling a file, and performing an ls (list directory) lookup. Make sure to add the JSch library to your project's dependencies.

import com.jcraft.jsch.*;    public class SftpExample {      public static void main(String[] args) {          String host = "sftp.example.com";          int port = 22;          String username = "your_username";          String privateKeyPath = "/path/to/your/private-key";          String passphrase = "your_passphrase";          String remoteDirectory = "/path/to/remote/directory/";            try {              JSch jsch = new JSch();                // Load the private key              jsch.addIdentity(privateKeyPath, passphrase);                // Create an sFTP session              Session session = jsch.getSession(username, host, port);              session.setConfig("PreferredAuthentications", "publickey,keyboard-interactive,password");              session.setConfig("StrictHostKeyChecking", "no"); // Disable host key checking (for development purposes only)              session.connect();                // Push a file to the remote directory              ChannelSftp channelSftp = (ChannelSftp) session.openChannel("sftp");              channelSftp.connect();              String localFilePath = "/path/to/local/file.txt";              channelSftp.put(localFilePath, remoteDirectory);              channelSftp.disconnect();                // Pull a file from the remote directory              channelSftp = (ChannelSftp) session.openChannel("sftp");              channelSftp.connect();              String remoteFileName = "file.txt"; // The name of the file on the remote server              String localDownloadPath = "/path/to/local/downloaded/file.txt";              channelSftp.get(remoteDirectory + remoteFileName, localDownloadPath);              channelSftp.disconnect();                // List files in the remote directory              channelSftp = (ChannelSftp) session.openChannel("sftp");              channelSftp.connect();              @SuppressWarnings("unchecked")              Vector<ChannelSftp.LsEntry> fileList = channelSftp.ls(remoteDirectory);              for (ChannelSftp.LsEntry entry : fileList) {                  System.out.println(entry.getFilename());              }              channelSftp.disconnect();                // Close the sFTP session              session.disconnect();          } catch (JSchException | SftpException e) {              e.printStackTrace();          }      }  }

Remember to replace placeholders like sftp.example.com, your_username, your_passphrase, and file paths with your actual information. This code connects to the sFTP server, pushes a file, pulls a file, and lists the files in the remote directory. Be cautious about security and best practices when dealing with sensitive data and private keys.

Security Considerations

Remember to secure your sFTP operations by using secure, encrypted connections and ensuring that your credentials are stored and managed securely. Consider using environment-specific properties or secret management tools to keep sensitive information safe.

In conclusion, efficient file transfer between a Spring Boot application and an sFTP server is a crucial part of many systems. By following these steps and best practices, you can ensure that your file transfer operations are reliable and secure. Whether you're pushing files to the server or pulling files from it, the process can be made seamless with the right tools and techniques. Happy coding!

A Momentary Pause: Embracing New Ventures and Gratitude

Post, Code and Quiet Time.

A Momentary Pause: Embracing New Ventures and Gratitude

By Errong Leng – 05 Aug 2023 – View online →

Photo by NEOM / Unsplash

Introduction:

Hello, dear readers of [errong.win]! It's been a bit quiet here for the past couple of months, and I owe you an explanation. Life has been a whirlwind of exciting activities and a dash of hard work. In this post, I'd like to take a moment to share with you the incredible journey that has kept me away from writing and how my team and I have been diligently crafting something wonderful behind the scenes.

The Birth of a New Project:

For the past two months, my energies have been fully immersed in a thrilling endeavor that I am truly proud of. I've been leading a dedicated team in launching an innovative project for my company. The goal was ambitious—to integrate our services with a top-tier carrier and deploy our solution to stores nationwide. The challenge was immense, but so was the determination of my hardworking team.

The Power of Teamwork:

I must say, my team has been nothing short of remarkable. Their dedication, creativity, and tireless efforts have been the driving force behind the successful integration and deployment. Together, we navigated through countless obstacles, brainstormed innovative solutions, and burnt the midnight oil to ensure a seamless nationwide rollout. Their passion has reminded me of the incredible strength that collaboration brings, and I am beyond grateful for each and every team member.

A Shining Achievement:

The moment of truth arrived as we celebrated the completion of the integration and deployment phase. Witnessing our project come to life in stores across the country was a surreal experience. It's a testament to the hard work, resilience, and commitment of everyone involved. We have not just launched a project; we've set a new milestone for our company and raised the bar for what we can achieve as a team.

Pause on the Blog, But Not on Gratitude:

I'm sure you've noticed the pause in blog posts during these intense months. Please know that this break was not due to a lack of dedication to this platform, but rather a temporary shift of focus to ensure the success of our project. I appreciate your understanding and continued support.

On a personal note, I've also been channeling some of my energies towards my personal blog, [errong.win]. It's been a labor of love, and I'm excited to share that my Google Adsense journey is progressing. I'm hoping that soon, you'll see relevant and interesting ads gracing the pages of my blog. Your support in this venture would mean the world to me, and I eagerly await Google's approval.

Google, please approve this time, the 5th request. finger crossed!

A Shoutout to ChatGPT:

Before I wrap up, I want to extend a heartfelt thank you to ChatGPT. In the late hours of the night, this incredible AI writing assistant has been my partner in penning down thoughts, ideas, and even entire blog posts. It's a true testament to the power of technology and its role in enabling creativity.

Conclusion:

As I return to my writing routine and the regular cadence of blog posts, I wanted to share this behind-the-scenes glimpse into the whirlwind that has been my life over the past two months. The journey has been invigorating, and I can't wait to continue sharing valuable insights, experiences, and stories with you, my amazing readers. Thank you for your unwavering support, and here's to new beginnings, teamwork, and the exciting future that lies ahead!

3 ways to speed up your nx react webpack app

Post, Code and Quiet Time.

3 ways to speed up your nx react webpack app

By Errong Leng – 06 May 2023 – View online →

Photo by The Cleveland Museum of Art / Unsplash

When it comes to user experience, a website’s loading time is one of the deciding success factors. The patience of visitors is steadily decreasing. Most of them will abandon a site if it doesn’t load within 3 seconds. For a business that means lost sales, leads, and opportunities. It’s a real sales killer.

In this post, I will share you 3 ways to speed up your web site loading time if it is build via nx, webpack and react.

Lazy-loading components with Suspense

lazy lets you defer loading component’s code until it is rendered for the first time.

import { lazy } from 'react';  const LazyComponent = lazy(() => import('./YourComponent.js'));    const UseLayComonent = () => {    return <Suspense fallback="loading">      <LazyComponent />    </Suspense>  }

Do not declare lazy components inside other components.
Instead, always declare them at the top level of your module.

For example, you are using react router, you might import all the components and use them as render component per route in your entry file. You might have lots of routes. But for the first initial load of an app, header, footer and root or home content are the most import parts. All other routes, we can defer loading them. By doing so in my recent app, the main.js file reduce its size from 3.6M to 1.2M.

use CompressionWebpackPlugin

@nrwl/react set up a default webpack configuration for your app. the build executor of this package does not compress the build assets by default.

module.exports = {    plugins: [      new CompressionPlugin({        threshold: 8192,      }),    ],  };

with the above webpack config, Only assets bigger than 8192 bytes are processed. We can custom @nrwl/react webpack config like below:

const nrwlConfig = require("@nrwl/react/plugins/webpack.js");  module.exports = (config) => {    nrwlConfig(config);    if (config.mode === "production") {      config.plugins.push(new CompressionPlugin({        threshold: 8192,      })    }    return config;  };

Then after run your app build, you will a .gz file generated for the assets size are bigger than 8192 size.

use expressStaticGzip

Provides a small layer on top of serve-static, which allows to serve pre-gzipped files. Supports brotli and allows configuring any other compression you can think of as well.

in case you are using express to serve your react web app, you can use expressStaticGzip.

use optimization. splitChunks

in case the vendor.js is too big, we can think of split it into multiple small ones. Modern browser are supporting parallel resource loading. Compare a single 10M vendors.js which takes about 5 seconds, I managed to split it into 3 smaller ones. The final webpack.js code:

use webpack-bundle-analyzer find the split points

Visualize size of webpack output files with an interactive zoomable tree map.

I found mui packages consist 45% of the build out main.js asset. so I split it out in the above code as a cacheGroup.

Notes: set different priority value for each cacheGroup, if you don't specify it in cacheGroup, it will default priority and only the last cacheGroup config will be used.

use HtmlWebpackPlugin

he HtmlWebpackPlugin simplifies creation of HTML files to serve your webpack bundles. This is especially useful for webpack bundles that include a hash in the filename which changes every compilation. You can either let the plugin generate an HTML file for you, supply your own template using lodash templates, or use your own loader.

Please push HtmlWebpackPlugin to your app's webpack configuration. Make sure you set scriptLoading to "module". @nrwl/react webpack config does not use HtmlWebpackPlugin by default. The reason why I added it because I want split vendors.js will be injected into build out assets index.html. If We don't use this plugin, even though CompressionWebpackPlugin can compress the build assets, The split vendor.js files will not be loaded in the index.html whilc would lead to your app not up.

References

lazy – React

The library for web and native user interfaces

CompressionWebpackPlugin | webpack

webpack is a module bundler. Its main purpose is to bundle JavaScript files for usage in a browser, yet it is also capable of transforming, bundling, or packaging just about any resource or asset.

webpack

Errong Leng

Automate Form Filling in PDFs Using iText 5 Library in Java

Efficient File Transfer: Pushing and Pulling Files Between a Spring Boot App and an sFTP Server

A Momentary Pause: Embracing New Ventures and Gratitude

Introduction:

The Birth of a New Project:

The Power of Teamwork:

A Shining Achievement:

Pause on the Blog, But Not on Gratitude:

A Shoutout to ChatGPT:

Conclusion:

3 ways to speed up your nx react webpack app

Lazy-loading components with Suspense

use CompressionWebpackPlugin

use expressStaticGzip

use optimization. splitChunks

use webpack-bundle-analyzer find the split points

use HtmlWebpackPlugin

References

QZ-L.com Enabled Limited Ads — A Small Step Forward

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Labels

Automate Form Filling in PDFs Using iText 5 Library in Java

Efficient File Transfer: Pushing and Pulling Files Between a Spring Boot App and an sFTP Server

A Momentary Pause: Embracing New Ventures and Gratitude

Introduction:

The Birth of a New Project:

The Power of Teamwork:

A Shining Achievement:

Pause on the Blog, But Not on Gratitude:

Google Adsense and New Horizons:

A Shoutout to ChatGPT:

Conclusion:

3 ways to speed up your nx react webpack app

Lazy-loading components with Suspense

use CompressionWebpackPlugin

use expressStaticGzip

use optimization. splitChunks

use webpack-bundle-analyzer find the split points

use HtmlWebpackPlugin

References

QZ-L.com Enabled Limited Ads — A Small Step Forward