bsh.Capabilities Maven / Gradle / Ivy
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/*****************************************************************************
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* This file is part of the BeanShell Java Scripting distribution. *
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package bsh;
import java.util.Hashtable;
/**
* The map of extended features supported by the runtime in which we live.
*
*
* This class should be independent of all other bsh classes!
*
*
* Note that tests for class existence here do *not* use the BshClassManager, as
* it may require other optional class files to be loaded.
*/
public class Capabilities {
private static boolean accessibility = false;
public static boolean haveSwing() {
// classExists caches info for us
return classExists("javax.swing.JButton");
}
public static boolean canGenerateInterfaces() {
// classExists caches info for us
return classExists("java.lang.reflect.Proxy");
}
/**
* If accessibility is enabled determine if the accessibility mechanism
* exists and if we have the optional bsh package to use it. Note that even
* if both are true it does not necessarily mean that we have runtime
* permission to access the fields... Java security has a say in it.
*
* @return whether this capabilities have accessibility or not.
* @see bsh.ReflectManager
*/
public static boolean haveAccessibility() {
return accessibility;
}
public static void setAccessibility(boolean b) throws Unavailable {
if (b == false) {
accessibility = false;
return;
}
if (!classExists("java.lang.reflect.AccessibleObject") || !classExists("bsh.reflect.ReflectManagerImpl"))
throw new Unavailable("Accessibility unavailable");
// test basic access
try {
String.class.getDeclaredMethods();
} catch (SecurityException e) {
throw new Unavailable("Accessibility unavailable: " + e);
}
accessibility = true;
}
private static Hashtable classes = new Hashtable();
/**
* Use direct Class.forName() to test for the existence of a class. We
* should not use BshClassManager here because: a) the systems using these
* tests would probably not load the classes through it anyway. b)
* bshclassmanager is heavy and touches other class files. this capabilities
* code must be light enough to be used by any system **including the remote
* applet**.
*
* @param name the name of a class.
* @return whether the class exists or not.
*/
public static boolean classExists(String name) {
Object c = classes.get(name);
if (c == null) {
try {
/*
* Note: do *not* change this to BshClassManager
* plainClassForName() or equivalent. This class must not touch
* any other bsh classes.
*/
c = Class.forName(name);
} catch (ClassNotFoundException e) {}
if (c != null)
classes.put(c, "unused");
}
return c != null;
}
/**
* An attempt was made to use an unavailable capability supported by an
* optional package. The normal operation is to test before attempting to
* use these packages... so this is runtime exception.
*/
public static class Unavailable extends UtilEvalError {
public Unavailable(String s) {
super(s);
}
}
}