NnClassLoader (Nashorn ClassLoader)

Simple and convenient Java ClassLoader for Nashorn scripts. Allows to define Java dependencies (jars, class directories, URLs, Maven or any combination of them) directly in the Nashorn script or right in jjs REPL.

Example of usage from jjs REPL without having any local jars or scripts and even without manual Maven installation:

jjs> // Load script with NnClassLoader from GitHub.
jjs> load('https://cdn.rawgit.com/NashornTools/NnClassLoader/master/NnClassLoader.js');
jjs>
jjs> // Define Maven dependencies for the script.
jjs> var MAVEN_DEPENDENCIES = ['com.h2database:h2:1.4.192', 'org.apache.commons:commons-dbcp2:2.1.1'];
jjs>
jjs> // Create class loader instance.
jjs> var L = new NnClassLoader({ maven: MAVEN_DEPENDENCIES });
jjs>
jjs> // Look at the actual list of jars resolved by the class loader.
jjs> for each(var url in L.getUrls()) print(url);
file:/Users/xxx/.m2/repository/com/h2database/h2/1.4.192/h2-1.4.192.jar
file:/Users/xxx/.m2/repository/org/apache/commons/commons-pool2/2.4.2/commons-pool2-2.4.2.jar
file:/Users/xxx/.m2/repository/commons-logging/commons-logging/1.2/commons-logging-1.2.jar
file:/Users/xxx/.m2/repository/org/apache/commons/commons-dbcp2/2.1.1/commons-dbcp2-2.1.1.jar
jjs>
jjs> // Import class similarly to Java.type('com.example.MyType').
jjs> var BasicDataSource = L.type('org.apache.commons.dbcp2.BasicDataSource');
jjs>
jjs> // Work with imported classes as usual.
jjs> var ds = new BasicDataSource();
jjs>
jjs> ds.setDriverClassName('org.h2.Driver');
jjs> ds.setUrl('jdbc:h2:mem:MyTestDb');
jjs>
jjs> var c = ds.getConnection();
jjs> var s = c.createStatement();
jjs>
jjs> s.executeUpdate('CREATE TABLE cars(name VARCHAR)');
0
jjs> s.executeUpdate("INSERT INTO cars VALUES ('BMW'),('Volvo'),('Lexus')");
3
jjs> var rs = s.executeQuery('SELECT * FROM cars');
jjs> while (rs.next()) print(rs.getString(1));
BMW
Volvo
Lexus

Supported configuration properties

NnClassLoader constructor accepts single object with any of the following configuration properties:

• urls - JS array of URL strings (may refer to remote Jars as well, e.g. {urls: ['http://example.com/bla.jar']})
• jars - JS array of Jar file path strings ({jars: ['libs/bla.jar']})
• dirs - JS array of directory path strings to be recursively scanned in order to find all the Jar files there ({dirs: ['libs']})
• filter - JS function which accepts single argument of type java.io.File and returns boolean; makes sense only if dirs is defined and allows to filter scanned files and directories ({dirs: ['libs'], filter: function(f) {return f.isDirectory() || f.getName().endsWith('.jar')}})
• classes - JS array of directory path strings to be added to classpath as is ({classes:['target/classes']})
• maven - JS array of Maven dependencies to be loaded ({maven: ['org.apache.ignite:ignite-core:1.7.0']})
• parent - parent Java class loader (must be of java.lang.ClassLoader type)

API methods of NnClassLoader instances

• type(className) - loads the requested type by name the same way as Java.type('...') does
• getUrls() - returnes JS array of actual URL strings used by this class loader instance
• getJavaClassLoader() - returns internal java.net.URLClassLoader instance which actually does the class loading (it is often useful to set it as a thread context class loader by java.lang.Thread.setContextClassLoader method)