What this project does?

This project implements Maven'ization of Apache Tomcat Native Library to produce a valid Maven artefact (POM and JAR)

No any changes made to the source code. I just added pom.xml and some test classes. All java source files are copied from released source tarball "as is".

Why it does that?

Apache Tomcat Native Library has no any Maven artefact nor any proper building toolchain for Java part.

Why do I need all this?

Apache Portable Library (APR) gives a full access to some tricky system features like memory-mapping files, special socket modes, file locking and other advanced features - just check project Java files.

The cool thing that it does it for all operating systems uniformly by introducing a new level of abstraction.

Who uses APR?

• Tomcat web container
• Netty.io library

Structure of APR / Tomcat Native

    [*      Apache Tomcat Native Library (Java classes, JAR)        *]
       java classes and definitions that knows about native part

                                 |
                                 | (uses)
                                \|/

    [* Apache Tomcat Native Library (Native part, libtcnative-1.so) *]
       JVM-aware native library that is facade between JVM and APR 

                                 |
                                 | (uses)
                                \|/

    [*     Apache Portable Runtime (Native part, libapr-1.so)       *]
        A level of abstraction that unifies features of different OS

                                 |
                                 | (uses)
                                \|/

    [*              Windows/Linux/Unix system API                   *]

Installation on Ubuntu 16.04

On other systems refer to your repositories.

Apache Portable Runtime (native part)

sudo apt-get install libapr1

Or just build the library from the sources.

Apache Tomcat Native Library (native part)

sudo apt-get install libtcnative-1

Also you can compile and install this library from the sources.

Apache Tomcat Native Library (java part)

To install this project to local Maven repository just install it with:

mvn clean install

Or/and deploy it to your team's Nexus repository.

A little tricky part

Check where you JVM is searching for native libraries:

String nativeLibPath = System.getProperty("java.library.path");
System.out.printf("JVM is searching native libraries in: %s%n", nativeLibPath);

# Oracle JDK 1.8 on Ubuntu 16.04 shows
# /opt/idea/default/bin::/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib

Then check where is libtcnative-1.so installed:

$ dpkg-query -L libtcnative-1 | grep libtcnative-1.so
/usr/lib/x86_64-linux-gnu/libtcnative-1.so.0.1.33
/usr/lib/x86_64-linux-gnu/libtcnative-1.so
/usr/lib/x86_64-linux-gnu/libtcnative-1.so.0

So here is problem - by default JDK is not seeing this library because JVM is not aware of that directory and JVM prints error when loading the native library:

org.apache.tomcat.jni.LibraryNotFoundError: no tcnative-1 in java.library.path, no libtcnative-1 in java.library.path 

But you can solve this problem in several ways.

1. make a symlink in some directory that is already known by JVM

    sudo mkdir -p /usr/java/packages/lib/amd64
    sudo ln -sfT /usr/lib/x86_64-linux-gnu/libtcnative-1.so /usr/java/packages/lib/amd64/libtcnative-1.so

2. ... or provide JVM with a special argument that points to the directory with the library

    java ... -Djava.library.path=/usr/lib/x86_64-linux-gnu ...

3. ... or set the search path for native libraries to the process (Linux only)

    export LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu
    java ...

Maven dependency

    <dependency>
        <groupId>org.apache.apr</groupId>
        <artifactId>tcnative</artifactId>
        <version>1.2.14</version>
    </dependency>

Usage

    boolean apr = Library.initialize(null);
    if (!apr) {
        throw new IllegalStateException("Fail to initialize Apache Tomcat Native library");
    }

    System.out.printf("Process PID=%d%n", Stdlib.getpid());
    System.out.printf("Parent  PID=%d%n", Stdlib.getppid());

References

Apache Portable Runtime (APR)

https://apr.apache.org/

https://apr.apache.org/anonsvn.html

https://apr.apache.org/docs/apr/1.6/index.html

Apache Tomcat Native Library

Native library and java part.

Repository: https://github.com/apache/tomcat-native

Note that Java part is automatically generated after native library is built.