README.md

Java Stream API Logger

Java Stream API Logger is an instrumentation library for logging of API methods returning Stream. It is needed when you want to understand what happens in the Streams created inside of your code.

Command Line to Use the Logger

java -Xbootclasspath/a:javassist-3.25.0-GA.jar;slf4j-api-2.0.0-alpha0.jar;java-stream-api-logger-1.0.jar -javaagent:java-stream-api-logger-1.0.jar <YourClass>

-Xbootclasspath/a is needed because java-stream-api-logger-1.0.jar contains a class injected into instrumented classes. javassist-3.25.0-GA.jar;slf4j-api-2.0.0-alpha0.jar are needed because java-stream-api-logger-1.0.jar uses them.

Dependencies

Your project needs to have a runtime dependency to any SLF4J implementation, e.g. runtime 'ch.qos.logback:logback-classic:1.3.0-alpha4', to see log messages.

Example

Code

package com.peshchuk.java.stream.api.logger.demo;

import java.util.stream.Stream;

public class Test {

  public static void main(String[] args) {
    final Integer min = Stream.iterate(1, i -> i + 1)
        .sequential()
        .map(i -> i + 1)
        .limit(5)
        .filter(i -> i % 2 == 0)
        .skip(1)
        .distinct()
        .sorted()
        .peek(i -> System.out.printf("Peek: %d\n", i))
        .min(Integer::compareTo)
        .orElse(-1);
    System.out.printf("Min: %d\n\n", min);
  }
}

Output

22:29:35.337 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.iterate - 1 (Test.java:17)
22:29:35.339 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.map - 2 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.limit - 2 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.filter - 2 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.iterate - 2 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.map - 3 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.limit - 3 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.iterate - 3 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.map - 4 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.limit - 4 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.filter - 4 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.skip - 4 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.distinct - 4 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.iterate - 4 (Test.java:17)
22:29:35.340 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.map - 5 (Test.java:17)
22:29:35.341 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.limit - 5 (Test.java:17)
22:29:35.341 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.iterate - 5 (Test.java:17)
22:29:35.341 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.map - 6 (Test.java:17)
22:29:35.341 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.limit - 6 (Test.java:17)
22:29:35.341 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.filter - 6 (Test.java:17)
22:29:35.341 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.skip - 6 (Test.java:17)
22:29:35.341 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.distinct - 6 (Test.java:17)
22:29:35.342 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.sorted - 4 (Test.java:17)
Peek: 4
22:29:35.345 [main] DEBUG com.peshchuk.java.stream.api.logger.demo.Test.main.sorted - 6 (Test.java:17)
Peek: 6
Min: 4