How to make an executable jar?

Question

I'm creating a new web application using Maven. I have got some code from 'spring's guides online which creates a database. However for some reason, the code is never being ran.

In my pom.xml, I have included the following code:

   <properties>
    <start-class>hello.Application</start-class>    
   </properties>

And this is the 'Application' class which I got from the spring guides.

package hello;

 import java.sql.ResultSet;

public class Application {

public static void main(String args[]) {
    // simple DS for test (not for production!)
    SimpleDriverDataSource dataSource = new SimpleDriverDataSource();
    dataSource.setDriverClass(org.h2.Driver.class);
    dataSource.setUsername("sa");
    dataSource.setUrl("jdbc:h2:mem");
    dataSource.setPassword("");

    JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);

    System.out.println("Creating tables");
    jdbcTemplate.execute("drop table customers if exists");
    jdbcTemplate.execute("create table customers(" +
            "id serial, first_name varchar(255), last_name varchar(255))");

    String[] names = "John Woo;Jeff Dean;Josh Bloch;Josh Long".split(";");
    for (String fullname : names) {
        String[] name = fullname.split(" ");
        System.out.printf("Inserting customer record for %s %s\n", name[0], name[1]);
        jdbcTemplate.update(
                "INSERT INTO customers(first_name,last_name) values(?,?)",
                name[0], name[1]);
    }

    System.out.println("Querying for customer records where first_name = 'Josh':");
    List<Customer> results = jdbcTemplate.query(
            "select * from customers where first_name = ?", new Object[] { "Josh" },
            new RowMapper<Customer>() {
                @Override
                public Customer mapRow(ResultSet rs, int rowNum) throws SQLException {
                    return new Customer(rs.getLong("id"), rs.getString("first_name"),
                            rs.getString("last_name"));
                }
            });

    for (Customer customer : results) {
        System.out.println(customer);
    }
}

}

My Project structure is as follows:

Project name

• src

  • webapp

    • hello

      • application.java

I am pretty new to this but I just can't see why its not finding the application.java file. Any ideas would be appreciated.

EDIT: This is the whole pom.xml

  <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/maven-v4_0_0.xsd">


 <modelVersion>4.0.0</modelVersion>
 <groupId>embed.tomcat.here</groupId>
 <artifactId>EmbedTomcatNew</artifactId>
 <packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>EmbedTomcatNew Maven Webapp</name>
<url>http://maven.apache.org</url>


  <properties>
    <start-class>hello.Application</start-class>    
</properties>

 <dependencies>
    <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>3.8.1</version>
    <scope>test</scope>
  </dependency>
 </dependencies>

 <build>
   <finalName>EmbedTomcatNew</finalName>
   <plugins>
           <plugin>
             <groupId>org.apache.tomcat.maven</groupId>
          <artifactId>tomcat7-maven-plugin</artifactId>
          <version>2.2</version>          
          <configuration>   
            <port>9966</port>
          </configuration>
        </plugin>
   </plugins>

   </build>

  </project>

EDIT: I should also mention that it is running a jsp file - which only has 'hello world' in it that prints to the browser - so it is running but I want it to run the java class first.

Answer 1

WAR

You are building a .war file, as evidenced in the <packaging>war</packaging> definition, which is only deployable to a Web Application container. There is no startup class, and as well documented on stackoverflow there is do way to control the order of startup in most web app containers.

JAR

You have to change your project to be an executable .jar and specify the main class in the Manifest in the jar plugin configuration options. Just setting some random property isn't going to do anything.

You probably want to use the shade plugin to bundle all the transient dependencies into a monolithic .jar as well otherwise you have an classpath installation nightmare on your hands.

Here is an example, running this from the src/main/webapp dir is a bad non-portable idea, that should be passed in as an argument.

import java.io.File;
import org.apache.catalina.startup.Tomcat;

public class Main {

    public static void main(String[] args) throws Exception {

        String webappDirLocation = "src/main/webapp/";
        Tomcat tomcat = new Tomcat();

        //The port that we should run on can be set into an environment variable
        //Look for that variable and default to 8080 if it isn't there.
        String webPort = System.getenv("PORT");
        if(webPort == null || webPort.isEmpty()) {
            webPort = "8080";
        }

        tomcat.setPort(Integer.valueOf(webPort));

        tomcat.addWebapp("/", new File(webappDirLocation).getAbsolutePath());
        System.out.println("configuring app with basedir: " + new File("./" + webappDirLocation).getAbsolutePath());

        tomcat.start();
        tomcat.getServer().await();
    }
}