Pipe

Simple java utility to act as a pipe (redirect input to output) with extended capabilities such as:

• Callback execution when pattern is found in input. You can configure a text pattern and a callback to be executed when a such pattern is found within any text line inside the pipe
• Suffix/prefix addition per line. For each piped line, you can add a prefix or suffix
• Header/footer addition Before or after text is piped, you can print a header or footer

Check the examples below

Usage

Maven

Add the maven dependency

<dependency>
    <groupId>net.benjaminguzman</groupId>
    <artifactId>Pipe</artifactId>
    <version>1.0.2</version>
</dependency>

Code

Usage is very easy:

Process proc = new ProcessBuilder("echo", "Command to run a process").start();

// initialize the pipe
Pipe pipe = new Pipe(
    new Pipe.Builder(proc.getInputStream(), System.out)
        .setPrefix("[Process]: ")
        .setHeader("--- BEGIN Process execution ---\n")
        .setFooter("--- END process execution ---\n")
        .setCloseOutStream(false) // if true System.out will be closed after pipe is finished
);

// start piping, thread is not needed but recommended, use pipe.run() to run without a thread
Thread t = pipe.initThread();
t.start();

Examples here use Process class, but you can use Pipe in other contexts

Full code example

import java.io.IOException;
import java.util.HashMap;
import java.util.concurrent.CountDownLatch;
import java.util.function.Consumer;
import java.util.regex.Pattern;

public class Example {
  public static void main(String... args) throws IOException, InterruptedException {
    CountDownLatch latch = new CountDownLatch(1); // latch to wait for the service to start
    HashMap<Pattern, Consumer<String>> map = new HashMap<>();
    map.put(
            Pattern.compile("Service is (up|running)"), // pattern to search (must be simple)
            s -> latch.countDown() // callback to execute when the pattern is found
    );

    // simulate a process start
    String echoString = "Starting service...\n" +
            "Configuration loaded\n" +
            "Starting something else inside service\n" +
            "Starting another thing or dependency\n" +
            "Service is running on 127.0.0.1:1111";
    Process proc = new ProcessBuilder("echo", "-e", echoString).start();

    // initialize the pipe
    Pipe pipe = new Pipe(
            new Pipe.Builder(proc.getInputStream(), System.out)
                    .setPrefix("[Service]: ")
                    .setHeader("--- BEGIN Service startup ---\n")
                    .setFooter("--- END Service startup (output was closed) ---\n")
                    .setHooks(map)
                    .setCloseOutStream(false) // if true System.out will be closed after pipe is finished
    );

    // start piping, thread is not needed but recommended, use pipe.run() to run without a thread
    Thread t = pipe.initThread();
    t.start();

    latch.await(); // wait until the latch is countdown (when pattern is found, see above)
    System.out.println("Service has started. It is time to run something else");

    t.join(); // wait for a clean shutdown
  }
}

You can find this full example in src/test/java/net/benjaminguzman/Example.java

Output

--- BEGIN Service startup ---
[Service]: Starting service...
[Service]: Configuration loaded
[Service]: Starting something else inside service
[Service]: Starting another thing or dependency
[Service]: Service is running on 127.0.0.1:1111
Service has started. It is time to run something else
--- END Service startup (output was closed)---

Note that the output is NOT

--- BEGIN Service startup ---
[Service]: Starting service...
[Service]: Configuration loaded
[Service]: Starting something else inside service
[Service]: Starting another thing or dependency
[Service]: Service is running on 127.0.0.1:1111
--- END Service startup (output was closed)---
Service has started. It is time to run something else

Because hooks (consumers) are executed as soon as the pattern is found

Test

Simply run

mvn clean test

to run tests

License

MIT license

Copyright © 2021 Benjamín Antonio Velasco Guzmán