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/***
* ASM examples: examples showing how ASM can be used
* Copyright (c) 2000-2011 INRIA, France Telecom
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import org.objectweb.asm.AnnotationVisitor;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
public class Annotations {
public static void foo(final @NotNull String arg) {
System.out.println(arg);
}
public static void main(final String[] args) throws Exception {
System.out
.println("Calling foo(null) results in a NullPointerException:");
try {
foo(null);
} catch (Exception e) {
e.printStackTrace(System.out);
}
final String n = Annotations.class.getName();
final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
ClassReader cr = new ClassReader(n);
cr.accept(new ClassVisitor(Opcodes.ASM4, cw) {
@Override
public MethodVisitor visitMethod(final int access,
final String name, final String desc,
final String signature, final String[] exceptions) {
final Type[] args = Type.getArgumentTypes(desc);
MethodVisitor v = cv.visitMethod(access, name, desc, signature,
exceptions);
return new MethodVisitor(Opcodes.ASM4, v) {
private final List<Integer> params = new ArrayList<Integer>();
@Override
public AnnotationVisitor visitParameterAnnotation(
final int parameter, final String desc,
final boolean visible) {
AnnotationVisitor av;
av = mv.visitParameterAnnotation(parameter, desc,
visible);
if (desc.equals("LNotNull;")) {
params.add(new Integer(parameter));
}
return av;
}
@Override
public void visitCode() {
int var = (access & Opcodes.ACC_STATIC) == 0 ? 1 : 0;
for (int p = 0; p < params.size(); ++p) {
int param = params.get(p).intValue();
for (int i = 0; i < param; ++i) {
var += args[i].getSize();
}
String c = "java/lang/IllegalArgumentException";
String d = "(Ljava/lang/String;)V";
Label end = new Label();
mv.visitVarInsn(Opcodes.ALOAD, var);
mv.visitJumpInsn(Opcodes.IFNONNULL, end);
mv.visitTypeInsn(Opcodes.NEW, c);
mv.visitInsn(Opcodes.DUP);
mv.visitLdcInsn("Argument " + param
+ " must not be null");
mv.visitMethodInsn(Opcodes.INVOKESPECIAL, c,
"<init>", d);
mv.visitInsn(Opcodes.ATHROW);
mv.visitLabel(end);
}
}
};
}
}, 0);
Class<?> c = new ClassLoader() {
@Override
public Class<?> loadClass(final String name)
throws ClassNotFoundException {
if (name.equals(n)) {
byte[] b = cw.toByteArray();
return defineClass(name, b, 0, b.length);
}
return super.loadClass(name);
}
}.loadClass(n);
System.out.println();
System.out.println("Calling foo(null) on the transformed class results"
+ " in an IllegalArgumentException:");
Method m = c.getMethod("foo", new Class<?>[] { String.class });
try {
m.invoke(null, new Object[] { null });
} catch (InvocationTargetException e) {
e.getCause().printStackTrace(System.out);
}
}
}
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