ctfield.java

Javassist是一个开源的分析、编辑和创建Java字节码的类库。是由东京技术学院的数学和计算机科学系的 Shigeru Chiba 所创建的。它已加入了开放源代码JBoss 应用服务器项目,通过使

                    CtClass[] parameters, Javac drv)
            throws CannotCompileException
        {
            if (parameters != null && nthParam < parameters.length) {
                code.addAload(0);
                int nth = nthParamToLocal(nthParam, parameters, false);
                int s = code.addLoad(nth, type) + 1;
                code.addPutfield(Bytecode.THIS, name, Descriptor.of(type));
                return s;       // stack size
            }
            else
                return 0;       // do not initialize
        }

        /**
         * Computes the index of the local variable that the n-th parameter
         * is assigned to.
         *
         * @param nth           n-th parameter
         * @param params                list of parameter types
         * @param isStatic              true if the method is static.
         */
        static int nthParamToLocal(int nth, CtClass[] params,
                                   boolean isStatic) {
            CtClass longType = CtClass.longType;
            CtClass doubleType = CtClass.doubleType;
            int k;
            if (isStatic)
                k = 0;
            else
                k = 1;  // 0 is THIS.

            for (int i = 0; i < nth; ++i) {
                CtClass type = params[i];
                if (type == longType || type == doubleType)
                    k += 2;
                else
                    ++k;
            }

            return k;
        }

        int compileIfStatic(CtClass type, String name, Bytecode code,
                            Javac drv) throws CannotCompileException
        {
            return 0;
        }
    }

    /**
     * A field initialized with an object created by the new operator.
     */
    static class NewInitializer extends Initializer {
        CtClass objectType;
        String[] stringParams;
        boolean withConstructorParams;

        NewInitializer() {}

        /**
         * Produces codes in which a new object is created and assigned to
         * the field as the initial value.
         */
        int compile(CtClass type, String name, Bytecode code,
                    CtClass[] parameters, Javac drv)
            throws CannotCompileException
        {
            int stacksize;

            code.addAload(0);
            code.addNew(objectType);
            code.add(Bytecode.DUP);
            code.addAload(0);

            if (stringParams == null)
                stacksize = 4;
            else
                stacksize = compileStringParameter(code) + 4;

            if (withConstructorParams)
                stacksize += CtNewWrappedMethod.compileParameterList(code,
                                                            parameters, 1);

            code.addInvokespecial(objectType, "<init>", getDescriptor());
            code.addPutfield(Bytecode.THIS, name, Descriptor.of(type));
            return stacksize;
        }

        private String getDescriptor() {
            final String desc3
        = "(Ljava/lang/Object;[Ljava/lang/String;[Ljava/lang/Object;)V";

            if (stringParams == null)
                if (withConstructorParams)
                    return "(Ljava/lang/Object;[Ljava/lang/Object;)V";
                else
                    return "(Ljava/lang/Object;)V";
            else
                if (withConstructorParams)
                    return desc3;
                else
                    return "(Ljava/lang/Object;[Ljava/lang/String;)V";
        }

        /**
         * Produces codes for a static field.
         */
        int compileIfStatic(CtClass type, String name, Bytecode code,
                            Javac drv) throws CannotCompileException
        {
            String desc;

            code.addNew(objectType);
            code.add(Bytecode.DUP);

            int stacksize = 2;
            if (stringParams == null)
                desc = "()V";
            else {
                desc = "([Ljava/lang/String;)V";
                stacksize += compileStringParameter(code);
            }

            code.addInvokespecial(objectType, "<init>", desc);
            code.addPutstatic(Bytecode.THIS, name, Descriptor.of(type));
            return stacksize;
        }

        protected final int compileStringParameter(Bytecode code)
            throws CannotCompileException
        {
            int nparam = stringParams.length;
            code.addIconst(nparam);
            code.addAnewarray(javaLangString);
            for (int j = 0; j < nparam; ++j) {
                code.add(Bytecode.DUP);         // dup
                code.addIconst(j);                      // iconst_<j>
                code.addLdc(stringParams[j]);   // ldc ...
                code.add(Bytecode.AASTORE);             // aastore
            }

            return 4;
        }

    }

    /**
     * A field initialized with the result of a static method call.
     */
    static class MethodInitializer extends NewInitializer {
        String methodName;
        // the method class is specified by objectType.

        MethodInitializer() {}

        /**
         * Produces codes in which a new object is created and assigned to
         * the field as the initial value.
         */
        int compile(CtClass type, String name, Bytecode code,
                    CtClass[] parameters, Javac drv)
            throws CannotCompileException
        {
            int stacksize;

            code.addAload(0);
            code.addAload(0);

            if (stringParams == null)
                stacksize = 2;
            else
                stacksize = compileStringParameter(code) + 2;

            if (withConstructorParams)
                stacksize += CtNewWrappedMethod.compileParameterList(code,
                                                            parameters, 1);

            String typeDesc = Descriptor.of(type);
            String mDesc = getDescriptor() + typeDesc;
            code.addInvokestatic(objectType, methodName, mDesc);
            code.addPutfield(Bytecode.THIS, name, typeDesc);
            return stacksize;
        }

        private String getDescriptor() {
            final String desc3
                = "(Ljava/lang/Object;[Ljava/lang/String;[Ljava/lang/Object;)";

            if (stringParams == null)
                if (withConstructorParams)
                    return "(Ljava/lang/Object;[Ljava/lang/Object;)";
                else
                    return "(Ljava/lang/Object;)";
            else
                if (withConstructorParams)
                    return desc3;
                else
                    return "(Ljava/lang/Object;[Ljava/lang/String;)";
        }

        /**
         * Produces codes for a static field.
         */
        int compileIfStatic(CtClass type, String name, Bytecode code,
                            Javac drv) throws CannotCompileException
        {
            String desc;

            int stacksize = 1;
            if (stringParams == null)
                desc = "()";
            else {
                desc = "([Ljava/lang/String;)";
                stacksize += compileStringParameter(code);
            }

            String typeDesc = Descriptor.of(type);
            code.addInvokestatic(objectType, methodName, desc + typeDesc);
            code.addPutstatic(Bytecode.THIS, name, typeDesc);
            return stacksize;
        }
    }

    static class IntInitializer extends Initializer {
        int value;

        IntInitializer(int v) { value = v; }

        void check(CtClass type) throws CannotCompileException {
            if (type != CtClass.intType)
                throw new CannotCompileException("type mismatch");
        }

        int compile(CtClass type, String name, Bytecode code,
                    CtClass[] parameters, Javac drv)
            throws CannotCompileException
        {
            code.addAload(0);
            code.addIconst(value);
            code.addPutfield(Bytecode.THIS, name, Descriptor.of(type));
            return 2;   // stack size
        }

        int compileIfStatic(CtClass type, String name, Bytecode code,
                            Javac drv) throws CannotCompileException
        {
            code.addIconst(value);
            code.addPutstatic(Bytecode.THIS, name, Descriptor.of(type));
            return 1;   // stack size
        }

        int getConstantValue(ConstPool cp, CtClass type) {
            if (type == CtClass.intType)
                return cp.addIntegerInfo(value);
            else
                return 0;
        }
    }

    static class LongInitializer extends Initializer {
        long value;

        LongInitializer(long v) { value = v; }

        void check(CtClass type) throws CannotCompileException {
            if (type != CtClass.longType)
                throw new CannotCompileException("type mismatch");
        }

        int compile(CtClass type, String name, Bytecode code,
                    CtClass[] parameters, Javac drv)
            throws CannotCompileException
        {
            code.addAload(0);
            code.addLdc2w(value);
            code.addPutfield(Bytecode.THIS, name, Descriptor.of(type));
            return 3;   // stack size
        }

        int compileIfStatic(CtClass type, String name, Bytecode code,
                            Javac drv) throws CannotCompileException
        {
            code.addLdc2w(value);
            code.addPutstatic(Bytecode.THIS, name, Descriptor.of(type));
            return 2;   // stack size
        }

        int getConstantValue(ConstPool cp, CtClass type) {
            if (type == CtClass.longType)
                return cp.addLongInfo(value);
            else
                return 0;
        }
    }

    static class DoubleInitializer extends Initializer {
        double value;

        DoubleInitializer(double v) { value = v; }

        void check(CtClass type) throws CannotCompileException {
            if (type != CtClass.doubleType)
                throw new CannotCompileException("type mismatch");
        }

        int compile(CtClass type, String name, Bytecode code,
                    CtClass[] parameters, Javac drv)
            throws CannotCompileException
        {
            code.addAload(0);
            code.addLdc2w(value);
            code.addPutfield(Bytecode.THIS, name, Descriptor.of(type));
            return 3;   // stack size
        }

        int compileIfStatic(CtClass type, String name, Bytecode code,
                            Javac drv) throws CannotCompileException
        {
            code.addLdc2w(value);
            code.addPutstatic(Bytecode.THIS, name, Descriptor.of(type));
            return 2;   // stack size
        }

        int getConstantValue(ConstPool cp, CtClass type) {
            if (type == CtClass.doubleType)
                return cp.addDoubleInfo(value);
            else
                return 0;
        }
    }

    static class StringInitializer extends Initializer {
        String value;

        StringInitializer(String v) { value = v; }

        void check(CtClass type) throws CannotCompileException {
            if (!type.getName().equals(javaLangString))
                throw new CannotCompileException("type mismatch");
        }

        int compile(CtClass type, String name, Bytecode code,
                    CtClass[] parameters, Javac drv)
            throws CannotCompileException
        {
            code.addAload(0);
            code.addLdc(value);
            code.addPutfield(Bytecode.THIS, name, Descriptor.of(type));
            return 2;   // stack size
        }

        int compileIfStatic(CtClass type, String name, Bytecode code,
                            Javac drv) throws CannotCompileException
        {
            code.addLdc(value);
            code.addPutstatic(Bytecode.THIS, name, Descriptor.of(type));
            return 1;   // stack size
        }

        int getConstantValue(ConstPool cp, CtClass type) {
            if (type.getName().equals(javaLangString))
                return cp.addStringInfo(value);
            else
                return 0;
        }
    }

    static class ArrayInitializer extends Initializer {
        CtClass type;
        int size;

        ArrayInitializer(CtClass t, int s) { type = t; size = s; }

        private void addNewarray(Bytecode code) {
            if (type.isPrimitive())
                code.addNewarray(((CtPrimitiveType)type).getArrayType(),
                                 size);
            else
                code.addAnewarray(type, size);
        }

        int compile(CtClass type, String name, Bytecode code,
                    CtClass[] parameters, Javac drv)
            throws CannotCompileException
        {
            code.addAload(0);
            addNewarray(code);
            code.addPutfield(Bytecode.THIS, name, Descriptor.of(type));
            return 2;   // stack size
        }

        int compileIfStatic(CtClass type, String name, Bytecode code,
                            Javac drv) throws CannotCompileException
        {
            addNewarray(code);
            code.addPutstatic(Bytecode.THIS, name, Descriptor.of(type));
            return 1;   // stack size
        }
    }

    static class MultiArrayInitializer extends Initializer {
        CtClass type;
        int[] dim;

        MultiArrayInitializer(CtClass t, int[] d) { type = t; dim = d; }

        void check(CtClass type) throws CannotCompileException {
            if (!type.isArray())
                throw new CannotCompileException("type mismatch");
        }

        int compile(CtClass type, String name, Bytecode code,
                    CtClass[] parameters, Javac drv)
            throws CannotCompileException
        {
            code.addAload(0);
            int s = code.addMultiNewarray(type, dim);
            code.addPutfield(Bytecode.THIS, name, Descriptor.of(type));
            return s + 1;       // stack size
        }

        int compileIfStatic(CtClass type, String name, Bytecode code,
                            Javac drv) throws CannotCompileException
        {
            int s = code.addMultiNewarray(type, dim);
            code.addPutstatic(Bytecode.THIS, name, Descriptor.of(type));
            return s;   // stack size
        }
    }
}