compiler.java

《移动Agent技术》一书的所有章节源代码。

/*
 * @(#)Compiler.java	1.4 98/02/26
 *
 * Copyright (c) 1995, 1996 Sun Microsystems, Inc. All Rights Reserved.
 *
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 *
 * CopyrightVersion 1.1_beta
 *
 */

package java.lang;

/**
 * The <code>Compiler</code> class is provided to support
 * Java-to-native-code compilers and related services. By design, the
 * <code>Compiler</code> class does nothing; it serves as a
 * placeholder for a JIT compiler implementation.
 * <p>
 * When the Java Virtual Machine first starts, it determines if the
 * system property <code>java.compiler</code> exists. (System
 * properties are accessible through <code>getProperty</code>  and ,
 * a method defined by the <code>System</code> class.) If so, it is
 * assumed to be the name of a library (with a platform-dependent
 * exact location and type); the <code>loadLibrary</code> method in
 * class <code>System</code> is called to load that library. If this
 * loading succeeds, the function named
 * <code>java_lang_Compiler_start()</code> in that library is called.
 * <p>
 * If no compiler is available, these methods do nothing.
 *
 * @author  Frank Yellin
 * @version 1.4, 02/26/98
 * @see     java.lang.System#getProperty(java.lang.String)
 * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
 * @see     java.lang.System#loadLibrary(java.lang.String)
 * @since   JDK1.0
 */
public final class Compiler  {
    private Compiler() {}		// don't make instances

    private static native void initialize();

    static {
	String library = null;
	try {
	    library = System.getProperty("java.compiler");
	    if ((library != null) && (!library.equals("")) &&
		/* to enable turning off the jit using an env var
		   on win32, it is not possible to set an env var
		   to an empty string on win32. */
		(!library.equals("NONE"))) {
		System.loadLibrary(library);
		initialize();
		}
	} catch (UnsatisfiedLinkError e) {
	    System.err.println("Warning: JIT compiler \"" + library +
			       "\" not found. Will use interpreter.");
	}
    }

    /**
     * Compiles the specified class.
     *
     * @param   clazz   a class.
     * @return  <code>true</code> if the compilation succeeded;
     *          <code>false</code> if the compilation failed or no compiler
     *          is available.
     * @since   JDK1.0
     */
    public static native boolean compileClass(Class clazz);

    /**
     * Compiles all classes whose name matches the specified string.
     *
     * @param   string   the name of the classes to compile.
     * @return  <code>true</code> if the compilation succeeded;
     *          <code>false</code> if the compilation failed or no compiler
     *          is available.
     * @since   JDK1.0
     */
    public static native boolean compileClasses(String string);

    /**
     * Examines the argument type and its fields and perform some documented
     * operation. No specific operations are required.
     *
     * @param   any   an argument.
     * @return  a compiler-specific value, or <code>null</code> if no compiler
     *          is available.
     * @since   JDK1.0
     */
    public static native Object command(Object any);

    /**
     * Cause the Compiler to resume operation.
     *
     * @since   JDK1.0
     */
    public static native void enable();

    /**
     * Cause the Compiler to cease operation.
     *
     * @since   JDK1.0
     */
    public static native void disable();
}