Java¶

Example¶

The Spring Music sample demonstrates a simple Spring application which can be bound to a MySQL or PostgreSQL data service.

Java Web Applications¶

The Java Web framework is the default Java framework in Helion Stackato, and requires little or no modification of application code in most cases. Helion Stackato deploys the war file.

Hello Java Sample demonstrates a simple Servlet-based Java webapp using the Java Web framework.

String stackato_services = System.getenv("STACKATO_SERVICES");

String hostname = NULL_STRING;
String dbname = NULL_STRING;
String user = NULL_STRING;
String password = NULL_STRING;
String port = NULL_STRING;

if (stackato_services != null && stackato_services.length() > 0) {
  try
  {
    JsonRootNode root = new JdomParser().parse(stackato_services);

    JsonNode credentials = root.getNode("mysql");

    dbname = credentials.getStringValue("name");
    hostname = credentials.getStringValue("hostname");
    user = credentials.getStringValue("user");
    password = credentials.getStringValue("password");
    port = credentials.getNumberValue("port");

    String dbUrl = "jdbc:mysql://" + hostname + ":" + port + "/" + dbname;

    Class.forName("com.mysql.jdbc.Driver");
    Connection connection = DriverManager.getConnection(dbUrl, user, password);
    return connection;

  }
  catch (Exception e)
  {
    throw new SQLException(e);
  }
}

JPDA Debugging¶

You can debug java_web applications running on Helion Stackato via JPDA by using the -d option with the stackato push command:

$ stackato push -d my-java-app

Helion Stackato creates a port service for debugging and shows the external port number in the command output:

Debugging now enabled on port 30135

Alternatively, request a Harbor port service in manifest.yml in the format *app-name*-debug. For example:

services:
  ${name}-debug: harbor

The java_web framework will recognize the service and activate debugging through the port provided. Connect to this port with the JPDA debugger of your choice.

To show the port number and external hostname for this service, use the stackato service command. For the my-java-app example above, the command would be:

$ stackato service my-java-app-debug

Use the hostname (or host for an IP address) and port values in the credentials section of the output to configure your local debugging client.

The STACKATO_DEBUG_COMMAND environment variable can be used to automatically start a debugger or IDE instance with the appropriate host and port values.

Spring¶

Applications that use the Spring framework are detected and automatically configured if there is either a spring-core jar file or an org/springframework directory.

<bean class="org.apache.commons.dbcp.BasicDataSource" id="dataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost:3306/inventory-db"/>
    <property name="username" value="myuser"/>
    <property name="password" value="mypass"/>
</bean>

JavaEE 6¶

The Stackato java_ee framework has two application servers available:

• TomEE - used for WAR files
• JBoss - used for EAR files

The Java EE framework is detected if there is a persistence.xml file located in src/main/resources/META-INF/persistence.xml*

services:
  service-1:
    type: mysql
  service-2:
    type: mysql

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
  xmlns="http://java.sun.com/xml/ns/persistence"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
    <persistence-unit name="persistence-service-1" transaction-type="JTA">
      <jta-datasource>service-1</jta-datasource>
    </persistence-unit>
</persistence>

@PersistenceContext(unitName = "persistence-service-1")
private EntityManager em;

HOME Directories¶

Java applications will have different HOME directories on Helion Stackato depending on which Java framework is used:

• Java Web, Java EE (war file), Spring, Lift and Grails: /home/stackato/tomcat/webapps/ROOT
• Java EE (ear file): /home/stackato/jboss/standalone/deployments
• Buildpack - Java, Play: /home/stackato/app

CATALINA_OPTS¶

The CATALINA_OPTS environment variable can be set in the env: block of manifest.yml (or set in the Management Console) to override Helion Stackato defaults.

Helion Stackato sets the CATALINA_OPTS environment variable for applications using Tomcat automatically, based on the memory: value specified for application instances. Helion Stackato will always leave at least 64MB for the heap, but will otherwise reserves up to 96MB for overhead, that is for the code of the JVM itself, for additional libraries loaded via JNI, for additional processes to run in the background, and for the JVM permanent pool.

This means, for example, a 128MB application will end up with 64MB for the heap and 64MB for overhead, a 160MB application will still have 64MB for the heap but 96MB for overhead, and a 512MB application will get a 416MB heap and allow 96MB for overhead.