How to import a external jar into the class-path of a running RCP application

Question

I have an Eclipse RCP application that run on clients machine. I need the RCP application to be able to import some third party jars (like Database connector Jars) to its class-path and then restart with the jars in the class-path.

I have tried to look everywhere but i cannot find a tutorial for it. I tried loading the jar using the following code:

urls = new URL[] { new URL("jar", "",
                "file:" + "C:\\Users\\Jars\\mysql-connector-java-5.1.38.jar" + "!/") };
        URLClassLoader cl = URLClassLoader.newInstance(urls, this.getClass().getClassLoader());
        Class<?> loadedClass = cl.loadClass("com.mysql.jdbc.Driver");

but this loads a single class. Even when i try loading all the classes in the jar, i am not able to get the internal dependencies resolved as the jar is not truly in the class-path of the RCP application.

The normal way to do it is by adding the path of the Jar in the Manifest.mf file and packaging the tool with the jar:

Bundle-ClassPath: Jars/mysql-connector-java-5.1.38.jar

But i cannot package the jar with the tool.

Most of the articles say to package the jars into plugins and provide the dependency. But can i do it at a client machine where the client just provides me with the path to the jar?

I have also read about the OSGI framework OSGI Tutorial by Vogel. But i am find it difficult to understand and i think it does not meet my requirement.

Ther are some RCP applications like SQLDeveloper those have the capablity of importing various JDBC jars in thier class-path and then restart with the jars in thie class-path. So i think it is possible.

Can anybody help me with this. Or redirrect me to a link? Thanks in advance

Answer 1

Please find following code.You can extend this in your RCP application.This code reads all the jar files in a particular folder location. For standalone application specifically

import java.io.File;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class MainClass {

public static void main(String[] args) {
    File jarFile = new File("Jar file location");
    for (File file : jarFile.listFiles()) {
        loadLibrary(file);
    }

    loadLibrary(jarFile);
    connectToDataBase();
}

private static void connectToDataBase() {
    try {
        Class.forName("org.apache.hadoop.hive.jdbc.HiveDriver");
        Connection con = DriverManager.getConnection("jdbc:hive://172.22.75.***:10000/DBNamE", "****",
                "***");
        Statement preparedStatement = con.createStatement();
        preparedStatement.executeQuery("use rapid");
        ResultSet resultSet = preparedStatement.executeQuery("select count (*) from flight");
        while (resultSet.next()) {
            System.out.println(resultSet.getString(1));
        }
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public static synchronized void loadLibrary(java.io.File jar) {
    try {
        java.net.URLClassLoader loader = (java.net.URLClassLoader) ClassLoader.getSystemClassLoader();
        java.net.URL url = jar.toURI().toURL();
        for (java.net.URL it : java.util.Arrays.asList(loader.getURLs())) {
            if (it.equals(url)) {
                return;
            }
        }
        java.lang.reflect.Method method = java.net.URLClassLoader.class.getDeclaredMethod("addURL",
                new Class[] { java.net.URL.class });
        method.setAccessible(
                true); /* promote the method to public access */
        method.invoke(loader, new Object[] { url });
    } catch (final java.lang.NoSuchMethodException | java.lang.IllegalAccessException
            | java.net.MalformedURLException | java.lang.reflect.InvocationTargetException e) {
        e.printStackTrace();
    }

}
}

For RCP based application specifically Load jar Class

public static synchronized void loadAllJars() {
        String path = System.getProperty("user.dir");
        System.out.println(path + "//jars" + " : Jar Path");
        System.out.println(System.getProperty("java.library.path") + " : Home path");
        File jarFile = new File(path + "//jars");
        for (File file : jarFile.listFiles()) {
            System.out.println("Loding jar : " + file.getName());
            try {
                URLClassLoader loader = (URLClassLoader) ClassLoader.getSystemClassLoader();
                URL url = file.toURI().toURL();
                for (URL it : Arrays.asList(loader.getURLs())) {
                    if (it.equals(url)) {
                        return;
                    }
                }
                Method method = URLClassLoader.class.getDeclaredMethod("addURL", new Class[] { URL.class });
                method.setAccessible(true);
                method.invoke(loader, new Object[] { url });
            } catch (final java.lang.NoSuchMethodException | java.lang.IllegalAccessException
                    | java.net.MalformedURLException | java.lang.reflect.InvocationTargetException e) {
                e.printStackTrace();
            }
        }
    }

Connect to Db

public class ConnectToDataBase {

    public static void connectToDataBase() {
        Connection con = null;
        String url = "jdbc:mysql://localhost:3306/employees";
        try {
            LoadJarUtil.loadAllJars();
            Properties properties = new Properties();
            properties.put("user", "****");
            properties.put("password", "****");
            @SuppressWarnings("unchecked")
            Class<Driver> driver = (Class<Driver>) Class.forName("org.apache.hadoop.hive.jdbc.HiveDriver", false,
                    ClassLoader.getSystemClassLoader());
            Connection connection = driver.newInstance().connect("jdbc:hive://172.22.***:10000", properties);
            System.out.println("Connected");
        } catch (Exception err) {
            err.printStackTrace();
        }
    }

}