Java Code Examples for org.springframework.expression.spel.CodeFlow#insertBoxIfNecessary()

/**
 * Ask an argument to generate its bytecode and then follow it up
 * with any boxing/unboxing/checkcasting to ensure it matches the expected parameter descriptor.
 */
protected static void generateCodeForArgument(MethodVisitor mv, CodeFlow cf, SpelNodeImpl argument, String paramDesc) {
	cf.enterCompilationScope();
	argument.generateCode(mv, cf);
	String lastDesc = cf.lastDescriptor();
	boolean primitiveOnStack = CodeFlow.isPrimitive(lastDesc);
	// Check if need to box it for the method reference?
	if (primitiveOnStack && paramDesc.charAt(0) == 'L') {
		CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
	}
	else if (paramDesc.length() == 1 && !primitiveOnStack) {
		CodeFlow.insertUnboxInsns(mv, paramDesc.charAt(0), lastDesc);
	}
	else if (!paramDesc.equals(lastDesc)) {
		// This would be unnecessary in the case of subtyping (e.g. method takes Number but Integer passed in)
		CodeFlow.insertCheckCast(mv, paramDesc);
	}
	cf.exitCompilationScope();
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	// exit type descriptor can be null if both components are literal expressions
	computeExitTypeDescriptor();
	this.children[0].generateCode(mv, cf);
	Label elseTarget = new Label();
	Label endOfIf = new Label();
	mv.visitInsn(DUP);
	mv.visitJumpInsn(IFNULL, elseTarget);
	mv.visitJumpInsn(GOTO, endOfIf);
	mv.visitLabel(elseTarget);
	mv.visitInsn(POP);
	this.children[1].generateCode(mv, cf);
	if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
		CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
	}
	mv.visitLabel(endOfIf);
	cf.pushDescriptor(this.exitTypeDescriptor);
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	getLeftOperand().generateCode(mv, cf);
	CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor());
	Assert.state(this.type != null, "No type available");
	if (this.type.isPrimitive()) {
		// always false - but left operand code always driven
		// in case it had side effects
		mv.visitInsn(POP);
		mv.visitInsn(ICONST_0); // value of false
	}
	else {
		mv.visitTypeInsn(INSTANCEOF, Type.getInternalName(this.type));
	}
	cf.pushDescriptor(this.exitTypeDescriptor);
}
 

/**
 * Ask an argument to generate its bytecode and then follow it up
 * with any boxing/unboxing/checkcasting to ensure it matches the expected parameter descriptor.
 */
protected static void generateCodeForArgument(MethodVisitor mv, CodeFlow cf, SpelNodeImpl argument, String paramDesc) {
	cf.enterCompilationScope();
	argument.generateCode(mv, cf);
	boolean primitiveOnStack = CodeFlow.isPrimitive(cf.lastDescriptor());
	// Check if need to box it for the method reference?
	if (primitiveOnStack && paramDesc.charAt(0) == 'L') {
		CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
	}
	else if (paramDesc.length() == 1 && !primitiveOnStack) {
		CodeFlow.insertUnboxInsns(mv, paramDesc.charAt(0), cf.lastDescriptor());
	}
	else if (!cf.lastDescriptor().equals(paramDesc)) {
		// This would be unnecessary in the case of subtyping (e.g. method takes Number but Integer passed in)
		CodeFlow.insertCheckCast(mv, paramDesc);
	}
	cf.exitCompilationScope();
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	// exit type descriptor can be null if both components are literal expressions
	computeExitTypeDescriptor();
	this.children[0].generateCode(mv, cf);
	CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
	Label elseTarget = new Label();
	Label endOfIf = new Label();
	mv.visitInsn(DUP);
	mv.visitJumpInsn(IFNULL, elseTarget);
	// Also check if empty string, as per the code in the interpreted version
	mv.visitInsn(DUP);
	mv.visitLdcInsn("");
	mv.visitInsn(SWAP);
	mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/String", "equals", "(Ljava/lang/Object;)Z",false);
	mv.visitJumpInsn(IFEQ, endOfIf);  // if not empty, drop through to elseTarget
	mv.visitLabel(elseTarget);
	mv.visitInsn(POP);
	this.children[1].generateCode(mv, cf);
	if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
		CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
	}
	mv.visitLabel(endOfIf);
	cf.pushDescriptor(this.exitTypeDescriptor);
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	cf.loadEvaluationContext(mv);
	String leftDesc = getLeftOperand().exitTypeDescriptor;
	String rightDesc = getRightOperand().exitTypeDescriptor;
	boolean leftPrim = CodeFlow.isPrimitive(leftDesc);
	boolean rightPrim = CodeFlow.isPrimitive(rightDesc);

	cf.enterCompilationScope();
	getLeftOperand().generateCode(mv, cf);
	cf.exitCompilationScope();
	if (leftPrim) {
		CodeFlow.insertBoxIfNecessary(mv, leftDesc.charAt(0));
	}
	cf.enterCompilationScope();
	getRightOperand().generateCode(mv, cf);
	cf.exitCompilationScope();
	if (rightPrim) {
		CodeFlow.insertBoxIfNecessary(mv, rightDesc.charAt(0));
	}

	String operatorClassName = Operator.class.getName().replace('.', '/');
	String evaluationContextClassName = EvaluationContext.class.getName().replace('.', '/');
	mv.visitMethodInsn(INVOKESTATIC, operatorClassName, "equalityCheck",
			"(L" + evaluationContextClassName + ";Ljava/lang/Object;Ljava/lang/Object;)Z", false);

	// Invert the boolean
	Label notZero = new Label();
	Label end = new Label();
	mv.visitJumpInsn(IFNE, notZero);
	mv.visitInsn(ICONST_1);
	mv.visitJumpInsn(GOTO, end);
	mv.visitLabel(notZero);
	mv.visitInsn(ICONST_0);
	mv.visitLabel(end);

	cf.pushDescriptor("Z");
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	cf.loadEvaluationContext(mv);
	String leftDesc = getLeftOperand().exitTypeDescriptor;
	String rightDesc = getRightOperand().exitTypeDescriptor;
	boolean leftPrim = CodeFlow.isPrimitive(leftDesc);
	boolean rightPrim = CodeFlow.isPrimitive(rightDesc);

	cf.enterCompilationScope();
	getLeftOperand().generateCode(mv, cf);
	cf.exitCompilationScope();
	if (leftPrim) {
		CodeFlow.insertBoxIfNecessary(mv, leftDesc.charAt(0));
	}
	cf.enterCompilationScope();
	getRightOperand().generateCode(mv, cf);
	cf.exitCompilationScope();
	if (rightPrim) {
		CodeFlow.insertBoxIfNecessary(mv, rightDesc.charAt(0));
	}

	String operatorClassName = Operator.class.getName().replace('.', '/');
	String evaluationContextClassName = EvaluationContext.class.getName().replace('.', '/');
	mv.visitMethodInsn(INVOKESTATIC, operatorClassName, "equalityCheck",
			"(L" + evaluationContextClassName + ";Ljava/lang/Object;Ljava/lang/Object;)Z", false);

	// Invert the boolean
	Label notZero = new Label();
	Label end = new Label();
	mv.visitJumpInsn(IFNE, notZero);
	mv.visitInsn(ICONST_1);
	mv.visitJumpInsn(GOTO, end);
	mv.visitLabel(notZero);
	mv.visitInsn(ICONST_0);
	mv.visitLabel(end);

	cf.pushDescriptor("Z");
}
 

void generateClinitCode(String clazzname, String constantFieldName, MethodVisitor mv, CodeFlow codeflow, boolean nested) {
	mv.visitTypeInsn(NEW, "java/util/ArrayList");
	mv.visitInsn(DUP);
	mv.visitMethodInsn(INVOKESPECIAL, "java/util/ArrayList", "<init>", "()V", false);
	if (!nested) {
		mv.visitFieldInsn(PUTSTATIC, clazzname, constantFieldName, "Ljava/util/List;");
	}
	int childcount = getChildCount();		
	for (int c=0; c < childcount; c++) {
		if (!nested) {
			mv.visitFieldInsn(GETSTATIC, clazzname, constantFieldName, "Ljava/util/List;");
		}
		else {
			mv.visitInsn(DUP);
		}
		// The children might be further lists if they are not constants. In this
		// situation do not call back into generateCode() because it will register another clinit adder.
		// Instead, directly build the list here:
		if (children[c] instanceof InlineList) {
			((InlineList)children[c]).generateClinitCode(clazzname, constantFieldName, mv, codeflow, true);
		}
		else {
			children[c].generateCode(mv, codeflow);
			if (CodeFlow.isPrimitive(codeflow.lastDescriptor())) {
				CodeFlow.insertBoxIfNecessary(mv, codeflow.lastDescriptor().charAt(0));
			}
		}
		mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true);
		mv.visitInsn(POP);
	}
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	cf.loadEvaluationContext(mv);
	String leftDesc = getLeftOperand().exitTypeDescriptor;
	String rightDesc = getRightOperand().exitTypeDescriptor;
	boolean leftPrim = CodeFlow.isPrimitive(leftDesc);
	boolean rightPrim = CodeFlow.isPrimitive(rightDesc);

	cf.enterCompilationScope();
	getLeftOperand().generateCode(mv, cf);
	cf.exitCompilationScope();
	if (leftPrim) {
		CodeFlow.insertBoxIfNecessary(mv, leftDesc.charAt(0));
	}
	cf.enterCompilationScope();
	getRightOperand().generateCode(mv, cf);
	cf.exitCompilationScope();
	if (rightPrim) {
		CodeFlow.insertBoxIfNecessary(mv, rightDesc.charAt(0));
	}

	String operatorClassName = Operator.class.getName().replace('.', '/');
	String evaluationContextClassName = EvaluationContext.class.getName().replace('.', '/');
	mv.visitMethodInsn(INVOKESTATIC, operatorClassName, "equalityCheck",
			"(L" + evaluationContextClassName + ";Ljava/lang/Object;Ljava/lang/Object;)Z", false);
	cf.pushDescriptor("Z");
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	// May reach here without it computed if all elements are literals
	computeExitTypeDescriptor();
	cf.enterCompilationScope();
	this.children[0].generateCode(mv, cf);
	String lastDesc = cf.lastDescriptor();
	Assert.state(lastDesc != null, "No last descriptor");
	if (!CodeFlow.isPrimitive(lastDesc)) {
		CodeFlow.insertUnboxInsns(mv, 'Z', lastDesc);
	}
	cf.exitCompilationScope();
	Label elseTarget = new Label();
	Label endOfIf = new Label();
	mv.visitJumpInsn(IFEQ, elseTarget);
	cf.enterCompilationScope();
	this.children[1].generateCode(mv, cf);
	if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
		lastDesc = cf.lastDescriptor();
		Assert.state(lastDesc != null, "No last descriptor");
		CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
	}
	cf.exitCompilationScope();
	mv.visitJumpInsn(GOTO, endOfIf);
	mv.visitLabel(elseTarget);
	cf.enterCompilationScope();
	this.children[2].generateCode(mv, cf);
	if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
		lastDesc = cf.lastDescriptor();
		Assert.state(lastDesc != null, "No last descriptor");
		CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
	}
	cf.exitCompilationScope();
	mv.visitLabel(endOfIf);
	cf.pushDescriptor(this.exitTypeDescriptor);
}
 

void generateClinitCode(String clazzname, String constantFieldName, MethodVisitor mv, CodeFlow codeflow, boolean nested) {
	mv.visitTypeInsn(NEW, "java/util/ArrayList");
	mv.visitInsn(DUP);
	mv.visitMethodInsn(INVOKESPECIAL, "java/util/ArrayList", "<init>", "()V", false);
	if (!nested) {
		mv.visitFieldInsn(PUTSTATIC, clazzname, constantFieldName, "Ljava/util/List;");
	}
	int childCount = getChildCount();
	for (int c = 0; c < childCount; c++) {
		if (!nested) {
			mv.visitFieldInsn(GETSTATIC, clazzname, constantFieldName, "Ljava/util/List;");
		}
		else {
			mv.visitInsn(DUP);
		}
		// The children might be further lists if they are not constants. In this
		// situation do not call back into generateCode() because it will register another clinit adder.
		// Instead, directly build the list here:
		if (this.children[c] instanceof InlineList) {
			((InlineList)this.children[c]).generateClinitCode(clazzname, constantFieldName, mv, codeflow, true);
		}
		else {
			this.children[c].generateCode(mv, codeflow);
			String lastDesc = codeflow.lastDescriptor();
			if (CodeFlow.isPrimitive(lastDesc)) {
				CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
			}
		}
		mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true);
		mv.visitInsn(POP);
	}
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	getLeftOperand().generateCode(mv, cf);
	CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor());
	if (this.type.isPrimitive()) {
		// always false - but left operand code always driven
		// in case it had side effects
		mv.visitInsn(POP);
		mv.visitInsn(ICONST_0); // value of false
	} 
	else {
		mv.visitTypeInsn(INSTANCEOF, Type.getInternalName(this.type));
	}
	cf.pushDescriptor(this.exitTypeDescriptor);
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	// exit type descriptor can be null if both components are literal expressions
	computeExitTypeDescriptor();
	cf.enterCompilationScope();
	this.children[0].generateCode(mv, cf);
	String lastDesc = cf.lastDescriptor();
	Assert.state(lastDesc != null, "No last descriptor");
	CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
	cf.exitCompilationScope();
	Label elseTarget = new Label();
	Label endOfIf = new Label();
	mv.visitInsn(DUP);
	mv.visitJumpInsn(IFNULL, elseTarget);
	// Also check if empty string, as per the code in the interpreted version
	mv.visitInsn(DUP);
	mv.visitLdcInsn("");
	mv.visitInsn(SWAP);
	mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/String", "equals", "(Ljava/lang/Object;)Z",false);
	mv.visitJumpInsn(IFEQ, endOfIf);  // if not empty, drop through to elseTarget
	mv.visitLabel(elseTarget);
	mv.visitInsn(POP);
	cf.enterCompilationScope();
	this.children[1].generateCode(mv, cf);
	if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
		lastDesc = cf.lastDescriptor();
		Assert.state(lastDesc != null, "No last descriptor");
		CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
	}
	cf.exitCompilationScope();
	mv.visitLabel(endOfIf);
	cf.pushDescriptor(this.exitTypeDescriptor);
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	cf.loadEvaluationContext(mv);
	String leftDesc = getLeftOperand().exitTypeDescriptor;
	String rightDesc = getRightOperand().exitTypeDescriptor;
	boolean leftPrim = CodeFlow.isPrimitive(leftDesc);
	boolean rightPrim = CodeFlow.isPrimitive(rightDesc);

	cf.enterCompilationScope();
	getLeftOperand().generateCode(mv, cf);
	cf.exitCompilationScope();
	if (leftPrim) {
		CodeFlow.insertBoxIfNecessary(mv, leftDesc.charAt(0));
	}
	cf.enterCompilationScope();
	getRightOperand().generateCode(mv, cf);
	cf.exitCompilationScope();
	if (rightPrim) {
		CodeFlow.insertBoxIfNecessary(mv, rightDesc.charAt(0));
	}

	String operatorClassName = Operator.class.getName().replace('.', '/');
	String evaluationContextClassName = EvaluationContext.class.getName().replace('.', '/');
	mv.visitMethodInsn(INVOKESTATIC, operatorClassName, "equalityCheck",
			"(L" + evaluationContextClassName + ";Ljava/lang/Object;Ljava/lang/Object;)Z", false);
	cf.pushDescriptor("Z");
}
 

void generateClinitCode(String clazzname, String constantFieldName, MethodVisitor mv, CodeFlow codeflow, boolean nested) {
	mv.visitTypeInsn(NEW, "java/util/ArrayList");
	mv.visitInsn(DUP);
	mv.visitMethodInsn(INVOKESPECIAL, "java/util/ArrayList", "<init>", "()V", false);
	if (!nested) {
		mv.visitFieldInsn(PUTSTATIC, clazzname, constantFieldName, "Ljava/util/List;");
	}
	int childCount = getChildCount();
	for (int c = 0; c < childCount; c++) {
		if (!nested) {
			mv.visitFieldInsn(GETSTATIC, clazzname, constantFieldName, "Ljava/util/List;");
		}
		else {
			mv.visitInsn(DUP);
		}
		// The children might be further lists if they are not constants. In this
		// situation do not call back into generateCode() because it will register another clinit adder.
		// Instead, directly build the list here:
		if (this.children[c] instanceof InlineList) {
			((InlineList)this.children[c]).generateClinitCode(clazzname, constantFieldName, mv, codeflow, true);
		}
		else {
			this.children[c].generateCode(mv, codeflow);
			String lastDesc = codeflow.lastDescriptor();
			if (CodeFlow.isPrimitive(lastDesc)) {
				CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
			}
		}
		mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true);
		mv.visitInsn(POP);
	}
}
 

/**
 * Generate the class that encapsulates the compiled expression and define it.
 * The  generated class will be a subtype of CompiledExpression.
 * @param expressionToCompile the expression to be compiled
 * @return the expression call, or {@code null} if the decision was to opt out of
 * compilation during code generation
 */
@SuppressWarnings("unchecked")
private Class<? extends CompiledExpression> createExpressionClass(SpelNodeImpl expressionToCompile) {
	// Create class outline 'spel/ExNNN extends org.springframework.expression.spel.CompiledExpression'
	String clazzName = "spel/Ex" + getNextSuffix();
	ClassWriter cw = new ExpressionClassWriter();
	cw.visit(V1_5, ACC_PUBLIC, clazzName, null, "org/springframework/expression/spel/CompiledExpression", null);

	// Create default constructor
	MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
	mv.visitCode();
	mv.visitVarInsn(ALOAD, 0);
	mv.visitMethodInsn(INVOKESPECIAL, "org/springframework/expression/spel/CompiledExpression",
			"<init>", "()V", false);
	mv.visitInsn(RETURN);
	mv.visitMaxs(1, 1);
	mv.visitEnd();

	// Create getValue() method
	mv = cw.visitMethod(ACC_PUBLIC, "getValue",
			"(Ljava/lang/Object;Lorg/springframework/expression/EvaluationContext;)Ljava/lang/Object;", null,
			new String[ ]{"org/springframework/expression/EvaluationException"});
	mv.visitCode();

	CodeFlow cf = new CodeFlow(clazzName, cw);

	// Ask the expression AST to generate the body of the method
	try {
		expressionToCompile.generateCode(mv, cf);
	}
	catch (IllegalStateException ex) {
		if (logger.isDebugEnabled()) {
			logger.debug(expressionToCompile.getClass().getSimpleName() +
					".generateCode opted out of compilation: " + ex.getMessage());
		}
		return null;
	}

	CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor());
	if ("V".equals(cf.lastDescriptor())) {
		mv.visitInsn(ACONST_NULL);
	}
	mv.visitInsn(ARETURN);

	mv.visitMaxs(0, 0);  // not supplied due to COMPUTE_MAXS
	mv.visitEnd();
	cw.visitEnd();

	cf.finish();

	byte[] data = cw.toByteArray();
	// TODO need to make this conditionally occur based on a debug flag
	// dump(expressionToCompile.toStringAST(), clazzName, data);
	return (Class<? extends CompiledExpression>) this.ccl.defineClass(clazzName.replaceAll("/", "."), data);
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	String leftDesc = getLeftOperand().exitTypeDescriptor;
	String rightDesc = getRightOperand().exitTypeDescriptor;
	Label elseTarget = new Label();
	Label endOfIf = new Label();
	boolean leftPrim = CodeFlow.isPrimitive(leftDesc);
	boolean rightPrim = CodeFlow.isPrimitive(rightDesc);

	DescriptorComparison dc = DescriptorComparison.checkNumericCompatibility(leftDesc, rightDesc,
			this.leftActualDescriptor, this.rightActualDescriptor);
	
	if (dc.areNumbers && dc.areCompatible) {
		char targetType = dc.compatibleType;
		
		getLeftOperand().generateCode(mv, cf);
		if (!leftPrim) {
			CodeFlow.insertUnboxInsns(mv, targetType, leftDesc);
		}
	
		cf.enterCompilationScope();
		getRightOperand().generateCode(mv, cf);
		cf.exitCompilationScope();
		if (!rightPrim) {
			CodeFlow.insertUnboxInsns(mv, targetType, rightDesc);
		}
		// assert: SpelCompiler.boxingCompatible(leftDesc, rightDesc)
		if (targetType=='D') {
			mv.visitInsn(DCMPL);
			mv.visitJumpInsn(IFNE, elseTarget);
		}
		else if (targetType=='F') {
			mv.visitInsn(FCMPL);		
			mv.visitJumpInsn(IFNE, elseTarget);
		}
		else if (targetType=='J') {
			mv.visitInsn(LCMP);		
			mv.visitJumpInsn(IFNE, elseTarget);
		}
		else if (targetType=='I' || targetType=='Z') {
			mv.visitJumpInsn(IF_ICMPNE, elseTarget);		
		}
		else {
			throw new IllegalStateException("Unexpected descriptor "+leftDesc);
		}
	}
	else {
		getLeftOperand().generateCode(mv, cf);
		if (leftPrim) {
			CodeFlow.insertBoxIfNecessary(mv, leftDesc.charAt(0));
		}
		getRightOperand().generateCode(mv, cf);
		if (rightPrim) {
			CodeFlow.insertBoxIfNecessary(mv, rightDesc.charAt(0));
		}
		Label leftNotNull = new Label();
		mv.visitInsn(DUP_X1); // Dup right on the top of the stack
		mv.visitJumpInsn(IFNONNULL,leftNotNull);
		// Right is null!
		mv.visitInsn(SWAP);
		mv.visitInsn(POP); // remove it
		Label rightNotNull = new Label();
		mv.visitJumpInsn(IFNONNULL, rightNotNull);
		// Left is null too
		mv.visitInsn(ICONST_1);
		mv.visitJumpInsn(GOTO, endOfIf);
		mv.visitLabel(rightNotNull);
		mv.visitInsn(ICONST_0);
		mv.visitJumpInsn(GOTO,endOfIf);
		mv.visitLabel(leftNotNull);
		mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Object", "equals", "(Ljava/lang/Object;)Z", false);
		mv.visitLabel(endOfIf);
		cf.pushDescriptor("Z");
		return;
	}
	mv.visitInsn(ICONST_1);
	mv.visitJumpInsn(GOTO,endOfIf);
	mv.visitLabel(elseTarget);
	mv.visitInsn(ICONST_0);
	mv.visitLabel(endOfIf);
	cf.pushDescriptor("Z");
}
 

/**
 * Generate the class that encapsulates the compiled expression and define it.
 * The  generated class will be a subtype of CompiledExpression.
 * @param expressionToCompile the expression to be compiled
 * @return the expression call, or {@code null} if the decision was to opt out of
 * compilation during code generation
 */
@Nullable
private Class<? extends CompiledExpression> createExpressionClass(SpelNodeImpl expressionToCompile) {
	// Create class outline 'spel/ExNNN extends org.springframework.expression.spel.CompiledExpression'
	String className = "spel/Ex" + getNextSuffix();
	ClassWriter cw = new ExpressionClassWriter();
	cw.visit(V1_5, ACC_PUBLIC, className, null, "org/springframework/expression/spel/CompiledExpression", null);

	// Create default constructor
	MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
	mv.visitCode();
	mv.visitVarInsn(ALOAD, 0);
	mv.visitMethodInsn(INVOKESPECIAL, "org/springframework/expression/spel/CompiledExpression",
			"<init>", "()V", false);
	mv.visitInsn(RETURN);
	mv.visitMaxs(1, 1);
	mv.visitEnd();

	// Create getValue() method
	mv = cw.visitMethod(ACC_PUBLIC, "getValue",
			"(Ljava/lang/Object;Lorg/springframework/expression/EvaluationContext;)Ljava/lang/Object;", null,
			new String[ ]{"org/springframework/expression/EvaluationException"});
	mv.visitCode();

	CodeFlow cf = new CodeFlow(className, cw);

	// Ask the expression AST to generate the body of the method
	try {
		expressionToCompile.generateCode(mv, cf);
	}
	catch (IllegalStateException ex) {
		if (logger.isDebugEnabled()) {
			logger.debug(expressionToCompile.getClass().getSimpleName() +
					".generateCode opted out of compilation: " + ex.getMessage());
		}
		return null;
	}

	CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor());
	if ("V".equals(cf.lastDescriptor())) {
		mv.visitInsn(ACONST_NULL);
	}
	mv.visitInsn(ARETURN);

	mv.visitMaxs(0, 0);  // not supplied due to COMPUTE_MAXS
	mv.visitEnd();
	cw.visitEnd();

	cf.finish();

	byte[] data = cw.toByteArray();
	// TODO need to make this conditionally occur based on a debug flag
	// dump(expressionToCompile.toStringAST(), clazzName, data);
	return loadClass(StringUtils.replace(className, "/", "."), data);
}
 

/**
 * Generate the class that encapsulates the compiled expression and define it.
 * The  generated class will be a subtype of CompiledExpression.
 * @param expressionToCompile the expression to be compiled
 * @return the expression call, or {@code null} if the decision was to opt out of
 * compilation during code generation
 */
@SuppressWarnings("unchecked")
private Class<? extends CompiledExpression> createExpressionClass(SpelNodeImpl expressionToCompile) {
	// Create class outline 'spel/ExNNN extends org.springframework.expression.spel.CompiledExpression'
	String clazzName = "spel/Ex" + getNextSuffix();
	ClassWriter cw = new ExpressionClassWriter();
	cw.visit(V1_5, ACC_PUBLIC, clazzName, null, "org/springframework/expression/spel/CompiledExpression", null);

	// Create default constructor
	MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
	mv.visitCode();
	mv.visitVarInsn(ALOAD, 0);
	mv.visitMethodInsn(INVOKESPECIAL, "org/springframework/expression/spel/CompiledExpression",
			"<init>", "()V", false);
	mv.visitInsn(RETURN);
	mv.visitMaxs(1, 1);
	mv.visitEnd();

	// Create getValue() method
	mv = cw.visitMethod(ACC_PUBLIC, "getValue",
			"(Ljava/lang/Object;Lorg/springframework/expression/EvaluationContext;)Ljava/lang/Object;", null,
			new String[ ]{"org/springframework/expression/EvaluationException"});
	mv.visitCode();

	CodeFlow cf = new CodeFlow(clazzName, cw);

	// Ask the expression AST to generate the body of the method
	try {
		expressionToCompile.generateCode(mv, cf);
	}
	catch (IllegalStateException ex) {
		if (logger.isDebugEnabled()) {
			logger.debug(expressionToCompile.getClass().getSimpleName() +
					".generateCode opted out of compilation: " + ex.getMessage());
		}
		return null;
	}

	CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor());
	if ("V".equals(cf.lastDescriptor())) {
		mv.visitInsn(ACONST_NULL);
	}
	mv.visitInsn(ARETURN);

	mv.visitMaxs(0, 0);  // not supplied due to COMPUTE_MAXS
	mv.visitEnd();
	cw.visitEnd();

	cf.finish();

	byte[] data = cw.toByteArray();
	// TODO need to make this conditionally occur based on a debug flag
	// dump(expressionToCompile.toStringAST(), clazzName, data);
	return (Class<? extends CompiledExpression>) this.ccl.defineClass(clazzName.replaceAll("/", "."), data);
}
 

@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
	CachedMethodExecutor executorToCheck = this.cachedExecutor;
	if (executorToCheck == null || !(executorToCheck.get() instanceof ReflectiveMethodExecutor)) {
		throw new IllegalStateException("No applicable cached executor found: " + executorToCheck);
	}

	ReflectiveMethodExecutor methodExecutor = (ReflectiveMethodExecutor) executorToCheck.get();
	Method method = methodExecutor.getMethod();
	boolean isStaticMethod = Modifier.isStatic(method.getModifiers());
	String descriptor = cf.lastDescriptor();

	if (descriptor == null) {
		if (!isStaticMethod) {
			// Nothing on the stack but something is needed
			cf.loadTarget(mv);
		}
	}
	else {
		if (isStaticMethod) {
			// Something on the stack when nothing is needed
			mv.visitInsn(POP);
		}
	}
	
	if (CodeFlow.isPrimitive(descriptor)) {
		CodeFlow.insertBoxIfNecessary(mv, descriptor.charAt(0));
	}

	String classDesc = (Modifier.isPublic(method.getDeclaringClass().getModifiers()) ?
			method.getDeclaringClass().getName().replace('.', '/') :
			methodExecutor.getPublicDeclaringClass().getName().replace('.', '/'));
	if (!isStaticMethod) {
		if (descriptor == null || !descriptor.substring(1).equals(classDesc)) {
			CodeFlow.insertCheckCast(mv, "L" + classDesc);
		}
	}

	generateCodeForArguments(mv, cf, method, this.children);
	mv.visitMethodInsn((isStaticMethod ? INVOKESTATIC : INVOKEVIRTUAL), classDesc, method.getName(),
			CodeFlow.createSignatureDescriptor(method), method.getDeclaringClass().isInterface());
	cf.pushDescriptor(this.exitTypeDescriptor);
}