docs/functions-package-java.md

id: functions-package-java title: Package Java Functions sidebar_label: “Package Java Functions” description: Learn to package Java functions in Pulsar.

:::note

If you plan to package and distribute your function for others to use, you are obligated to license and copyright your own code properly. Remember to add the license and copyright to all libraries your code uses and to your distribution.

If you use the NAR method, the NAR plugin automatically creates a DEPENDENCIES file in the generated NAR package, including the proper licensing and copyrights of all libraries of your function.

For the runtime Java version, refer to Pulsar Runtime Java Version Recommendation according to your target Pulsar version.

:::

There are two methods to package Java Functions:

Package as JAR

To package a Java function as JAR, complete the following steps.

Create a new maven project with a pom file. In the following code sample, the value of mainClass is your package name.

 <?xml version="1.0" encoding="UTF-8"?>
 <project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>

     <groupId>java-function</groupId>
     <artifactId>java-function</artifactId>
     <version>1.0-SNAPSHOT</version>

     <dependencies>
         <dependency>
             <groupId>org.apache.pulsar</groupId>
             <artifactId>pulsar-functions-api</artifactId>
             <version>@pulsar:version@</version>
         </dependency>
     </dependencies>

     <build>
         <plugins>
             <plugin>
                 <artifactId>maven-assembly-plugin</artifactId>
                 <configuration>
                     <appendAssemblyId>false</appendAssemblyId>
                     <descriptorRefs>
                         <descriptorRef>jar-with-dependencies</descriptorRef>
                     </descriptorRefs>
                     <archive>
                     <manifest>
                         <mainClass>org.example.test.ExclamationFunction</mainClass>
                     </manifest>
                 </archive>
                 </configuration>
                 <executions>
                     <execution>
                         <id>make-assembly</id>
                         <phase>package</phase>
                         <goals>
                             <goal>assembly</goal>
                         </goals>
                     </execution>
                 </executions>
             </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.11.0</version>
                 <configuration>
                     <release>17</release>
                 </configuration>
             </plugin>
         </plugins>
     </build>

 </project>

Package your Java function.
```
 mvn package
```
After the Java function is packaged, a target directory is created automatically. Open the target directory to check if there is a JAR package similar to java-function-1.0-SNAPSHOT.jar.

Run the Java function using the following command.

 ./bin/pulsar-admin functions localrun \
    --classname org.example.test.ExclamationFunction \
    --jar $PWD/target/java-function-1.0-SNAPSHOT.jar \
    --inputs persistent://public/default/my-topic-1 \
    --output persistent://public/default/test-1 \
    --tenant public \
    --namespace default \
    --name JavaFunction

The following log indicates that the Java function starts successfully.

 ...
 07:55:03.724 [main] INFO  org.apache.pulsar.functions.runtime.ProcessRuntime - Started process successfully
 ...

Package as NAR

To package a Java function as NAR, complete the following steps.

Create a new maven project with a pom file.

 <?xml version="1.0" encoding="UTF-8"?>
 <project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>

     <groupId>java-function</groupId>
     <artifactId>java-function</artifactId>
     <version>1.0-SNAPSHOT</version>

     <dependencies>
         <dependency>
             <groupId>org.apache.pulsar</groupId>
             <artifactId>pulsar-functions-api</artifactId>
             <version>@pulsar:version@</version>
         </dependency>
     </dependencies>

     <build>
         <plugins>
             <plugin>
                 <groupId>org.apache.nifi</groupId>
                 <artifactId>nifi-nar-maven-plugin</artifactId>
                 <version>1.5.0</version>
                 </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.11.0</version>
                 <configuration>
                     <release>17</release>
                 </configuration>
             </plugin>
         </plugins>
     </build>

 </project>

You must also create a resources/META-INF/services/pulsar-io.yaml file. In the following code sample, the value of functionClass is your function class name. The name is the one used when the Function is deployed as a built-in one.

name: java-function
description: my java function
functionClass: org.example.test.ExclamationFunction

Package your Java function.
```
mvn package
```
After the Java function is packaged, a target directory is created automatically. Open the target directory to check if there is a NAR package similar to java-function-1.0-SNAPSHOT.nar.

Run the Java function using the following command.

 ./bin/pulsar-admin functions localrun \
    --jar $PWD/target/java-function-1.0-SNAPSHOT.nar \
    --inputs persistent://public/default/my-topic-1 \
    --output persistent://public/default/test-1 \
    --tenant public \
    --namespace default \
    --name JavaFunction

The following log indicates that the Java function starts successfully.

 ...
 07:55:03.724 [main] INFO  org.apache.pulsar.functions.runtime.ProcessRuntime - Started process successfully
 ...