Java tutorial
// ASM: a very small and fast Java bytecode manipulation framework // 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. package org.objectweb.asm; /** * A visitor to visit a Java class. The methods of this class must be called in the following order: * {@code visit} [ {@code visitSource} ] [ {@code visitModule} ][ {@code visitNestHost} ][ {@code * visitPermittedSubtype} ][ {@code visitOuterClass} ] ( {@code visitAnnotation} | {@code * visitTypeAnnotation} | {@code visitAttribute} )* ( {@code visitNestMember} | {@code * visitInnerClass} | {@code visitField} | {@code visitMethod} )* {@code visitEnd}. * * @author Eric Bruneton */ public abstract class ClassVisitor { /** * The ASM API version implemented by this visitor. The value of this field must be one of {@link * Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}. */ protected final int api; /** The class visitor to which this visitor must delegate method calls. May be {@literal null}. */ protected ClassVisitor cv; /** * Constructs a new {@link ClassVisitor}. * * @param api the ASM API version implemented by this visitor. Must be one of {@link * Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}. */ public ClassVisitor(final int api) { this(api, null); } /** * Constructs a new {@link ClassVisitor}. * * @param api the ASM API version implemented by this visitor. Must be one of {@link * Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}. * @param classVisitor the class visitor to which this visitor must delegate method calls. May be * null. */ public ClassVisitor(final int api, final ClassVisitor classVisitor) { if (api != Opcodes.ASM7 && api != Opcodes.ASM6 && api != Opcodes.ASM5 && api != Opcodes.ASM4 && api != Opcodes.ASM8_EXPERIMENTAL) { throw new IllegalArgumentException("Unsupported api " + api); } if (api == Opcodes.ASM8_EXPERIMENTAL) { Constants.checkAsm8Experimental(this); } this.api = api; this.cv = classVisitor; } /** * Visits the header of the class. * * @param version the class version. The minor version is stored in the 16 most significant bits, * and the major version in the 16 least significant bits. * @param access the class's access flags (see {@link Opcodes}). This parameter also indicates if * the class is deprecated. * @param name the internal name of the class (see {@link Type#getInternalName()}). * @param signature the signature of this class. May be {@literal null} if the class is not a * generic one, and does not extend or implement generic classes or interfaces. * @param superName the internal of name of the super class (see {@link Type#getInternalName()}). * For interfaces, the super class is {@link Object}. May be {@literal null}, but only for the * {@link Object} class. * @param interfaces the internal names of the class's interfaces (see {@link * Type#getInternalName()}). May be {@literal null}. */ public void visit(final int version, final int access, final String name, final String signature, final String superName, final String[] interfaces) { if (cv != null) { cv.visit(version, access, name, signature, superName, interfaces); } } /** * Visits the source of the class. * * @param source the name of the source file from which the class was compiled. May be {@literal * null}. * @param debug additional debug information to compute the correspondence between source and * compiled elements of the class. May be {@literal null}. */ public void visitSource(final String source, final String debug) { if (cv != null) { cv.visitSource(source, debug); } } /** * Visit the module corresponding to the class. * * @param name the fully qualified name (using dots) of the module. * @param access the module access flags, among {@code ACC_OPEN}, {@code ACC_SYNTHETIC} and {@code * ACC_MANDATED}. * @param version the module version, or {@literal null}. * @return a visitor to visit the module values, or {@literal null} if this visitor is not * interested in visiting this module. */ public ModuleVisitor visitModule(final String name, final int access, final String version) { if (api < Opcodes.ASM6) { throw new UnsupportedOperationException("This feature requires ASM6"); } if (cv != null) { return cv.visitModule(name, access, version); } return null; } /** * Visits the nest host class of the class. A nest is a set of classes of the same package that * share access to their private members. One of these classes, called the host, lists the other * members of the nest, which in turn should link to the host of their nest. This method must be * called only once and only if the visited class is a non-host member of a nest. A class is * implicitly its own nest, so it's invalid to call this method with the visited class name as * argument. * * @param nestHost the internal name of the host class of the nest. */ public void visitNestHost(final String nestHost) { if (api < Opcodes.ASM7) { throw new UnsupportedOperationException("This feature requires ASM7"); } if (cv != null) { cv.visitNestHost(nestHost); } } /** * Visits the enclosing class of the class. This method must be called only if the class has an * enclosing class. * * @param owner internal name of the enclosing class of the class. * @param name the name of the method that contains the class, or {@literal null} if the class is * not enclosed in a method of its enclosing class. * @param descriptor the descriptor of the method that contains the class, or {@literal null} if * the class is not enclosed in a method of its enclosing class. */ public void visitOuterClass(final String owner, final String name, final String descriptor) { if (cv != null) { cv.visitOuterClass(owner, name, descriptor); } } /** * Visits an annotation of the class. * * @param descriptor the class descriptor of the annotation class. * @param visible {@literal true} if the annotation is visible at runtime. * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not * interested in visiting this annotation. */ public AnnotationVisitor visitAnnotation(final String descriptor, final boolean visible) { if (cv != null) { return cv.visitAnnotation(descriptor, visible); } return null; } /** * Visits an annotation on a type in the class signature. * * @param typeRef a reference to the annotated type. The sort of this type reference must be * {@link TypeReference#CLASS_TYPE_PARAMETER}, {@link * TypeReference#CLASS_TYPE_PARAMETER_BOUND} or {@link TypeReference#CLASS_EXTENDS}. See * {@link TypeReference}. * @param typePath the path to the annotated type argument, wildcard bound, array element type, or * static inner type within 'typeRef'. May be {@literal null} if the annotation targets * 'typeRef' as a whole. * @param descriptor the class descriptor of the annotation class. * @param visible {@literal true} if the annotation is visible at runtime. * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not * interested in visiting this annotation. */ public AnnotationVisitor visitTypeAnnotation(final int typeRef, final TypePath typePath, final String descriptor, final boolean visible) { if (api < Opcodes.ASM5) { throw new UnsupportedOperationException("This feature requires ASM5"); } if (cv != null) { return cv.visitTypeAnnotation(typeRef, typePath, descriptor, visible); } return null; } /** * Visits a non standard attribute of the class. * * @param attribute an attribute. */ public void visitAttribute(final Attribute attribute) { if (cv != null) { cv.visitAttribute(attribute); } } /** * Visits a member of the nest. A nest is a set of classes of the same package that share access * to their private members. One of these classes, called the host, lists the other members of the * nest, which in turn should link to the host of their nest. This method must be called only if * the visited class is the host of a nest. A nest host is implicitly a member of its own nest, so * it's invalid to call this method with the visited class name as argument. * * @param nestMember the internal name of a nest member. */ public void visitNestMember(final String nestMember) { if (api < Opcodes.ASM7) { throw new UnsupportedOperationException("This feature requires ASM7"); } if (cv != null) { cv.visitNestMember(nestMember); } } /** * <b>Experimental, use at your own risk. This method will be renamed when it becomes stable, this * will break existing code using it</b>. Visits a permitted subtypes. A permitted subtypes is one * of the allowed subtypes of the current class. * * @param permittedSubtype the internal name of a permitted subtype. * @deprecated this API is experimental. */ @Deprecated public void visitPermittedSubtypeExperimental(final String permittedSubtype) { if (api != Opcodes.ASM8_EXPERIMENTAL) { throw new UnsupportedOperationException("This feature requires ASM8_EXPERIMENTAL"); } if (cv != null) { cv.visitPermittedSubtypeExperimental(permittedSubtype); } } /** * Visits information about an inner class. This inner class is not necessarily a member of the * class being visited. * * @param name the internal name of an inner class (see {@link Type#getInternalName()}). * @param outerName the internal name of the class to which the inner class belongs (see {@link * Type#getInternalName()}). May be {@literal null} for not member classes. * @param innerName the (simple) name of the inner class inside its enclosing class. May be * {@literal null} for anonymous inner classes. * @param access the access flags of the inner class as originally declared in the enclosing * class. */ public void visitInnerClass(final String name, final String outerName, final String innerName, final int access) { if (cv != null) { cv.visitInnerClass(name, outerName, innerName, access); } } /** * Visits a record component of the class. * * @param access the record component access flags, the only possible value is {@link * Opcodes#ACC_DEPRECATED}. * @param name the record component name. * @param descriptor the record component descriptor (see {@link Type}). * @param signature the record component signature. May be {@literal null} if the record component * type does not use generic types. * @return a visitor to visit this record component annotations and attributes, or {@literal null} * if this class visitor is not interested in visiting these annotations and attributes. * @deprecated this API is experimental. */ @Deprecated public RecordComponentVisitor visitRecordComponentExperimental(final int access, final String name, final String descriptor, final String signature) { if (api < Opcodes.ASM8_EXPERIMENTAL) { throw new UnsupportedOperationException("This feature requires ASM8_EXPERIMENTAL"); } if (cv != null) { return cv.visitRecordComponentExperimental(access, name, descriptor, signature); } return null; } /** * Visits a field of the class. * * @param access the field's access flags (see {@link Opcodes}). This parameter also indicates if * the field is synthetic and/or deprecated. * @param name the field's name. * @param descriptor the field's descriptor (see {@link Type}). * @param signature the field's signature. May be {@literal null} if the field's type does not use * generic types. * @param value the field's initial value. This parameter, which may be {@literal null} if the * field does not have an initial value, must be an {@link Integer}, a {@link Float}, a {@link * Long}, a {@link Double} or a {@link String} (for {@code int}, {@code float}, {@code long} * or {@code String} fields respectively). <i>This parameter is only used for static * fields</i>. Its value is ignored for non static fields, which must be initialized through * bytecode instructions in constructors or methods. * @return a visitor to visit field annotations and attributes, or {@literal null} if this class * visitor is not interested in visiting these annotations and attributes. */ public FieldVisitor visitField(final int access, final String name, final String descriptor, final String signature, final Object value) { if (cv != null) { return cv.visitField(access, name, descriptor, signature, value); } return null; } /** * Visits a method of the class. This method <i>must</i> return a new {@link MethodVisitor} * instance (or {@literal null}) each time it is called, i.e., it should not return a previously * returned visitor. * * @param access the method's access flags (see {@link Opcodes}). This parameter also indicates if * the method is synthetic and/or deprecated. * @param name the method's name. * @param descriptor the method's descriptor (see {@link Type}). * @param signature the method's signature. May be {@literal null} if the method parameters, * return type and exceptions do not use generic types. * @param exceptions the internal names of the method's exception classes (see {@link * Type#getInternalName()}). May be {@literal null}. * @return an object to visit the byte code of the method, or {@literal null} if this class * visitor is not interested in visiting the code of this method. */ public MethodVisitor visitMethod(final int access, final String name, final String descriptor, final String signature, final String[] exceptions) { if (cv != null) { return cv.visitMethod(access, name, descriptor, signature, exceptions); } return null; } /** * Visits the end of the class. This method, which is the last one to be called, is used to inform * the visitor that all the fields and methods of the class have been visited. */ public void visitEnd() { if (cv != null) { cv.visitEnd(); } } }