javac.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

            if (index < numOfLocalVars)
                gen.recordVariable(va.descriptor(i), va.variableName(i),
                                   index, stable);
        }

        return true;
    }


    /**
     * Makes variables $0 (this), $1, $2, ..., and $args represent method
     * parameters.  $args represents an array of all the parameters.
     * It also makes $$ available as a parameter list of method call.
     *
     * <p>This must be called before calling <code>compileStmnt()</code> and
     * <code>compileExpr()</code>.  The correct value of
     * <code>isStatic</code> must be recorded before compilation.
     * <code>maxLocals</code> is updated to include $0,...
     */
    public int recordParams(CtClass[] params, boolean isStatic)
        throws CompileError
    {
        return gen.recordParams(params, isStatic, "$", "$args", "$$", stable);
    }

    /**
     * Makes variables $0, $1, $2, ..., and $args represent method
     * parameters.  $args represents an array of all the parameters.
     * It also makes $$ available as a parameter list of method call.
     * $0 can represent a local variable other than THIS (variable 0).
     * $class is also made available.
     *
     * <p>This must be called before calling <code>compileStmnt()</code> and
     * <code>compileExpr()</code>.  The correct value of
     * <code>isStatic</code> must be recorded before compilation.
     * <code>maxLocals</code> is updated to include $0,...
     *
     * @paaram use0     true if $0 is used.
     * @param varNo     the register number of $0 (use0 is true)
     *                          or $1 (otherwise).
     * @param target    the type of $0 (it can be null if use0 is false).
     *                  It is used as the name of the type represented
     *                  by $class.
     * @param isStatic  true if the method in which the compiled bytecode
     *                  is embedded is static.
     */
    public int recordParams(String target, CtClass[] params,
                             boolean use0, int varNo, boolean isStatic)
        throws CompileError
    {
        return gen.recordParams(params, isStatic, "$", "$args", "$$",
                                use0, varNo, target, stable);
    }

    /**
     * Sets <code>maxLocals</code> to <code>max</code>.
     * This method tells the compiler the local variables that have been
     * allocated for the rest of the code.  When the compiler needs
     * new local variables, the local variables at the index <code>max</code>,
     * <code>max + 1</code>, ... are assigned.
     *
     * <p>This method is indirectly called by <code>recordParams</code>.
     */
    public void setMaxLocals(int max) {
        gen.setMaxLocals(max);
    }

    /**
     * Prepares to use cast $r, $w, $_, and $type.
     * $type is made to represent the specified return type.
     * It also enables to write a return statement with a return value
     * for void method.
     *
     * <p>If the return type is void, ($r) does nothing.
     * The type of $_ is java.lang.Object.
     *
     * @param type              the return type.
     * @param useResultVar      true if $_ is used.
     * @return          -1 or the variable index assigned to $_.
     * @see #recordType(CtClass)
     */
    public int recordReturnType(CtClass type, boolean useResultVar)
        throws CompileError
    {
        gen.recordType(type);
        return gen.recordReturnType(type, "$r",
                        (useResultVar ? resultVarName : null), stable);
    }

    /**
     * Prepares to use $type.  Note that recordReturnType() overwrites
     * the value of $type.
     *
     * @param t     the type represented by $type.
     */
    public void recordType(CtClass t) {
        gen.recordType(t);
    }

    /**
     * Makes the given variable available.
     *
     * @param type      variable type
     * @param name      variable name
     */
    public int recordVariable(CtClass type, String name)
        throws CompileError
    {
        return gen.recordVariable(type, name, stable);
    }

    /**
     * Prepares to use $proceed().
     * If the return type of $proceed() is void, null is pushed on the
     * stack.
     *
     * @param target    an expression specifying the target object.
     *                          if null, "this" is the target.
     * @param method    the method name.
     */
    public void recordProceed(String target, String method)
        throws CompileError
    {
        Parser p = new Parser(new Lex(target));
        final ASTree texpr = p.parseExpression(stable);
        final String m = method;

        ProceedHandler h = new ProceedHandler() {
                public void doit(JvstCodeGen gen, Bytecode b, ASTList args)
                    throws CompileError
                {
                    ASTree expr = new Member(m);
                    if (texpr != null)
                        expr = Expr.make('.', texpr, expr);

                    expr = CallExpr.makeCall(expr, args);
                    gen.compileExpr(expr);
                    gen.addNullIfVoid();
                }

                public void setReturnType(JvstTypeChecker check, ASTList args)
                    throws CompileError
                {
                    ASTree expr = new Member(m);
                    if (texpr != null)
                        expr = Expr.make('.', texpr, expr);

                    expr = CallExpr.makeCall(expr, args);
                    expr.accept(check);
                    check.addNullIfVoid();
                }
            };

        gen.setProceedHandler(h, proceedName);
    }

    /**
     * Prepares to use $proceed() representing a static method.
     * If the return type of $proceed() is void, null is pushed on the
     * stack.
     *
     * @param targetClass    the fully-qualified dot-separated name
     *				of the class declaring the method.
     * @param method         the method name.
     */
    public void recordStaticProceed(String targetClass, String method)
        throws CompileError
    {
        final String c = targetClass;
        final String m = method;

        ProceedHandler h = new ProceedHandler() {
                public void doit(JvstCodeGen gen, Bytecode b, ASTList args)
                    throws CompileError
                {
                    Expr expr = Expr.make(TokenId.MEMBER,
                                          new Symbol(c), new Member(m));
                    expr = CallExpr.makeCall(expr, args);
                    gen.compileExpr(expr);
                    gen.addNullIfVoid();
                }

                public void setReturnType(JvstTypeChecker check, ASTList args)
                    throws CompileError
                {
                    Expr expr = Expr.make(TokenId.MEMBER,
                                          new Symbol(c), new Member(m));
                    expr = CallExpr.makeCall(expr, args);
                    expr.accept(check);
                    check.addNullIfVoid();
                }
            };

        gen.setProceedHandler(h, proceedName);
    }

    /**
     * Prepares to use $proceed() representing a private/super's method.
     * If the return type of $proceed() is void, null is pushed on the
     * stack.  This method is for methods invoked by INVOKESPECIAL.
     *
     * @param target    an expression specifying the target object.
     *                          if null, "this" is the target.
     * @param classname	    the class name declaring the method.
     * @param methodname    the method name.
     * @param descriptor    the method descriptor.
     */
    public void recordSpecialProceed(String target, String classname,
                                     String methodname, String descriptor)
        throws CompileError
    {
        Parser p = new Parser(new Lex(target));
        final ASTree texpr = p.parseExpression(stable);
        final String cname = classname;
        final String method = methodname;
        final String desc = descriptor;

        ProceedHandler h = new ProceedHandler() {
                public void doit(JvstCodeGen gen, Bytecode b, ASTList args)
                    throws CompileError
                {
                    gen.compileInvokeSpecial(texpr, cname, method, desc, args);
                }

                public void setReturnType(JvstTypeChecker c, ASTList args)
                    throws CompileError
                {
                    c.compileInvokeSpecial(texpr, cname, method, desc, args);
                }

            };

        gen.setProceedHandler(h, proceedName);
    }

    /**
     * Prepares to use $proceed().
     */
    public void recordProceed(ProceedHandler h) {
        gen.setProceedHandler(h, proceedName);
    }

    /**
     * Compiles a statement (or a block).
     * <code>recordParams()</code> must be called before invoking
     * this method.
     *
     * <p>Local variables that are not declared
     * in the compiled source text might not be accessible within that
     * source text.  Fields and method parameters ($0, $1, ..) are available.
     */
    public void compileStmnt(String src) throws CompileError {
        Parser p = new Parser(new Lex(src));
        SymbolTable stb = new SymbolTable(stable);
        while (p.hasMore()) {
            Stmnt s = p.parseStatement(stb);
            if (s != null)
                s.accept(gen);
        }
    }

    /**
     * Compiles an exression.  <code>recordParams()</code> must be
     * called before invoking this method.
     *
     * <p>Local variables are not accessible
     * within the compiled source text.  Fields and method parameters
     * ($0, $1, ..) are available if <code>recordParams()</code>
     * have been invoked.
     */
    public void compileExpr(String src) throws CompileError {
        ASTree e = parseExpr(src, stable);
        compileExpr(e);
    }

    /**
     * Parsers an expression.
     */
    public static ASTree parseExpr(String src, SymbolTable st)
        throws CompileError
    {
        Parser p = new Parser(new Lex(src));
        return p.parseExpression(st);
    }

    /**
     * Compiles an exression.  <code>recordParams()</code> must be
     * called before invoking this method.
     *
     * <p>Local variables are not accessible
     * within the compiled source text.  Fields and method parameters
     * ($0, $1, ..) are available if <code>recordParams()</code>
     * have been invoked.
     */
    public void compileExpr(ASTree e) throws CompileError {
        if (e != null)
            gen.compileExpr(e);
    }
}