Use URLClassLoader load jar files into classpath

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class LoadJarClassloader {
	private static final String PROTOCAL_PREFIX = "file:///";

	public static ClassLoader getProjectClassLoader(String[] classPaths) throws MalformedURLException {

		// compute the project classpaths
		// REVIEW: Are the classpaths returned by computeDefaultRuntimeClassPath
		// enough to load class?
		URL[] urls = new URL[classPaths.length];
		for (int i = 0; i < classPaths.length; i++) {
			urls[i] = new URL(PROTOCAL_PREFIX + computeForURLClassLoader(classPaths[i]));
		}
		return new URLClassLoader(urls, Thread.currentThread().getContextClassLoader());
	}

	/**
	 * load <code>Class</code> in java project
	 * 
	 * @param project
	 *            <code>IJavaProject</code>
	 * @param className
	 *            name of class to load
	 * @return <code>Class</code>
	 * @throws ClassNotFoundException
	 * @throws CoreException
	 * @throws MalformedURLException
	 */
	public static Class loadClass(String className) throws ClassNotFoundException, MalformedURLException {
		ClassLoader loader = getProjectClassLoader(new String[] { "E:\\Projects\\LoadJar\\lib\\commons-dbcp-1.2.1.jar",
				"E:\\Projects\\LoadJar\\lib\\02182701940.jar" });
		Class clazz = loader.loadClass(className);
		loader = null;
		return clazz;
	}
	public static ClassLoader getClassLoader() throws ClassNotFoundException, MalformedURLException {
		ClassLoader loader = getProjectClassLoader(new String[] { "E:\\Projects\\LoadJar\\lib\\commons-dbcp-1.2.1.jar",
				"E:\\Projects\\LoadJar\\lib\\mysql-connector-java-3.0.14-mikuni-bin.jar" });
//		Class clazz = loader.loadClass(className);
//		loader = null;
		return loader;
	}
	public static void main(String[] args) throws MalformedURLException, ClassNotFoundException, SQLException, InstantiationException, IllegalAccessException {
		Class clazz = loadClass("com.mysql.jdbc.Driver");
		Driver driver = (Driver)clazz.newInstance();
		String url = "jdbc:mysql://localhost:3306/test";
		String username = "root";
		String password = "reversea1";
		// 加载驱动程序以连接数据库
//		Class.forName("com.mysql.jdbc.Driver",true,getClassLoader());
		Properties info = new Properties();
		info.setProperty("user", username);
		info.setProperty("password", password);
		Connection connection = driver.connect(url, info );
		
		System.out.println(connection.toString());
	}

	/**
	 * transform the <code>IType</code> to <code>Class</code>
	 * 
	 * @param type
	 *            <code>IType</code>
	 * @return <code>Class</code>
	 * @throws ClassNotFoundException
	 * @throws MalformedURLException
	 */
	// public static Class typeToClass(IType type)
	// ClassNotFoundException,MalformedURLException {
	// if (null != type && (type.isClass() || type.isInterface())) {
	// String className = type.getFullyQualifiedName('$');
	// return loadClass(type.getJavaProject(), className);
	// }
	//        
	// return null;
	// }
	/**
	 * because of URLClassLoader assumes any URL not ends with '/' to refer to a
	 * jar file. so we need to append '/' to classpath if it is a folder but not
	 * ends with '/'.
	 * 
	 * @param classpath
	 * @return
	 */
	private static String computeForURLClassLoader(String classpath) {
		if (!classpath.endsWith("/")) {
			File file = new File(classpath);
			if (file.exists() && file.isDirectory()) {
				classpath = classpath.concat("/");
			}
		}
		return classpath;
	}
}

评论

1 楼 reverocean 2008-11-06  

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