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30 import java.lang.reflect.InvocationTargetException  ;
31 import java.lang.reflect.Method ;
32 import java.util.ArrayList ;
33 import java.util.List ;
34
35 import org.objectweb.asm.AnnotationVisitor;
36 import org.objectweb.asm.ClassAdapter;
37 import org.objectweb.asm.ClassReader;
38 import org.objectweb.asm.ClassWriter;
39 import org.objectweb.asm.Label;
40 import org.objectweb.asm.MethodAdapter;
41 import org.objectweb.asm.MethodVisitor;
42 import org.objectweb.asm.Opcodes;
43 import org.objectweb.asm.Type;
44
45 public class Annotations {
46
47 public static void foo(final @NotNull
48 String arg)
49 {
50 System.out.println(arg);
51 }
52
53 public static void main(final String [] args) throws Exception {
54 System.out.println("Calling foo(null) results in a NullPointerException:");
55 try {
56 foo(null);
57 } catch (Exception e) {
58 e.printStackTrace(System.out);
59 }
60
61 final String n = Annotations.class.getName();
62 final ClassWriter cw = new ClassWriter(true);
63 ClassReader cr = new ClassReader(n);
64 cr.accept(new ClassAdapter(cw) {
65
66 public MethodVisitor visitMethod(
67 final int access,
68 final String name,
69 final String desc,
70 final String signature,
71 final String [] exceptions)
72 {
73 final Type[] args = Type.getArgumentTypes(desc);
74 MethodVisitor v = cv.visitMethod(access,
75 name,
76 desc,
77 signature,
78 exceptions);
79 return new MethodAdapter(v) {
80
81 private List params = new ArrayList ();
82
83 public AnnotationVisitor visitParameterAnnotation(
84 final int parameter,
85 final String desc,
86 final boolean visible)
87 {
88 AnnotationVisitor av;
89 av = mv.visitParameterAnnotation(parameter,
90 desc,
91 visible);
92 if (desc.equals("LNotNull;")) {
93 params.add(new Integer (parameter));
94 }
95 return av;
96 }
97
98 public void visitCode() {
99 int var = ((access & Opcodes.ACC_STATIC) == 0) ? 1 : 0;
100 for (int p = 0; p < params.size(); ++p) {
101 int param = ((Integer ) params.get(p)).intValue();
102 for (int i = 0; i < param; ++i) {
103 var += args[i].getSize();
104 }
105 String c = "java/lang/IllegalArgumentException";
106 String d = "(Ljava/lang/String;)V";
107 Label end = new Label();
108 mv.visitVarInsn(Opcodes.ALOAD, var);
109 mv.visitJumpInsn(Opcodes.IFNONNULL, end);
110 mv.visitTypeInsn(Opcodes.NEW, c);
111 mv.visitInsn(Opcodes.DUP);
112 mv.visitLdcInsn("Argument " + param
113 + " must not be null");
114 mv.visitMethodInsn(Opcodes.INVOKESPECIAL,
115 c,
116 "<init>",
117 d);
118 mv.visitInsn(Opcodes.ATHROW);
119 mv.visitLabel(end);
120 }
121 }
122 };
123 }
124 }, false);
125
126 Class c = new ClassLoader () {
127 public Class loadClass(final String name)
128 throws ClassNotFoundException
129 {
130 if (name.equals(n)) {
131 byte[] b = cw.toByteArray();
132 return defineClass(name, b, 0, b.length);
133 }
134 return super.loadClass(name);
135 }
136 }.loadClass(n);
137
138 System.out.println();
139 System.out.println("Calling foo(null) on the transformed class results in an IllegalArgumentException:");
140 Method m = c.getMethod("foo", new Class [] { String .class });
141 try {
142 m.invoke(null, new Object [] { null });
143 } catch (InvocationTargetException e) {
144 e.getCause().printStackTrace(System.out);
145 }
146 }
147 }
148 |
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