Java

Install

First things first, let’s make sure the correct versions of Java and Maven are installed.

Head over here and install the Java and Maven versions listed:

Versions

Next, let’s create a totally new Maven project for testing.

mvn archetype:generate -DgroupId=com.mycompany.app -DartifactId=my-app -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4 -DinteractiveMode=false

Now, open the pom.xml file, delete its contents, and replace it with the following:

<?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>com.mycompany.app</groupId>
  <artifactId>my-app</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>my-app</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <poly.version>0.15.1</poly.version>
  </properties>
  <dependencies>
    <dependency>
      <groupId>io.polyapi</groupId>
      <artifactId>library</artifactId>
      <version>${poly.version}</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <build>
    <resources>
      <resource>
        <directory>target/generated-resources</directory>
      </resource>
    </resources>
    <plugins>
      <plugin>
        <groupId>io.polyapi</groupId>
        <artifactId>polyapi-maven-plugin</artifactId>
        <version>${poly.version}</version>
        <configuration>
          <host>{HOST}</host>
          <port>443</port>
          <apiKey>{$env.API_KEY}</apiKey>
        </configuration>
        <executions>
          <execution>
            <phase>generate-sources</phase>
            <goals>
              <goal>generate-sources</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.12.1</version>
        <configuration>
          <parameters>true</parameters>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>build-helper-maven-plugin</artifactId>
        <version>3.2.0</version>
        <executions>
          <execution>
            <id>add-source</id>
            <phase>generate-sources</phase>
            <goals>
              <goal>add-source</goal>
            </goals>
            <configuration>
              <sources>
                <source>target/generated-sources</source>
              </sources>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

Next:

  • Replace {HOST} with the server you’re connecting to (e.g. https://na1.polyapi.io)

  • Create a new environment variable named POLY_API_KEY with its value as your api key. The code {$env.POLY_API_KEY} in the above example will pull from your api key from the environment.

Warning

The pom.xml file is generally checked into git. Be sure to not check in your api key. Instead, use an environment variable as shown above.

Then run this command to ensure the library is installed:

mvn clean compile

Develop First Function

Next, let’s develop our first custom function!

In your project, create a new Java file named Greetings.java next to App.java in ./my-app/main/java/com/mycompany/app with the following contents:

package com.mycompany.app;

import io.polyapi.commons.api.model.PolyServerFunction;

public class Greetings {

  @PolyServerFunction(context="greetings")
  public String hello(String name) {
    return String.format("Hello %s", name);
  }
}

Next use the PolyAPI Maven plugin to deploy this function:

mvn clean compile polyapi:deploy-functions

This will deploy a new server function to Poly. You can also instead use the @PolyClientFunction annotation instead of @PolyServerFunction to create functions which are packaged into the generated SDK.

Run First Function

To generate the code invocation of an uploaded server function you need to compile the project once again:

$ mvn clean compile

Now let’s execute the function. Go back to your App.java file that was generated and replace its contents with the following:

package com.mycompany.app;

import io.polyapi.Poly;

public class App {

  public static void main(String[] args) {
    System.out.println(Poly.greetings.hello("Alice"));
  }
}

Note

Keep in mind that the Poly invocation follows the structure:

Poly.[function context].[function name](...)

To customize those values, the @PolyServerFunction or @PolyClientFunction annotations provide the name and context arguments.

We used the context argument "greetings" in the example above.

We did not specify a name argument, so by default the function name became the method name hello.

Finally run the java app with the following command:

mvn exec:java -Dexec.mainClass="com.mycompany.app.App" -Dexec.cleanupDaemonThreads=false

You should see the following output:

Hello Alice

Congratulations! You have successfully created and executed your first server function.

Onward

That’s it! You have now:

  • Setup your Java SDK

  • Trained your first server function

  • Ran your first server function

This is the last step on the guided tour of Poly.

To further explore aspects of Poly and what it can do, head over to Next Steps.