/*
* Copyright 2002-2016 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.expression.spel.ast;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.springframework.asm.ClassWriter;
import org.springframework.asm.MethodVisitor;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.CodeFlow;
import org.springframework.expression.spel.ExpressionState;
import org.springframework.expression.spel.SpelNode;
/**
* Represent a list in an expression, e.g. '{1,2,3}'
*
* @author Andy Clement
* @since 3.0.4
*/
public class InlineList extends SpelNodeImpl {
// If the list is purely literals, it is a constant value and can be computed and cached
private TypedValue constant = null; // TODO must be immutable list
public InlineList(int pos, SpelNodeImpl... args) {
super(pos, args);
checkIfConstant();
}
/**
* If all the components of the list are constants, or lists that themselves contain constants, then a constant list
* can be built to represent this node. This will speed up later getValue calls and reduce the amount of garbage
* created.
*/
private void checkIfConstant() {
boolean isConstant = true;
for (int c = 0, max = getChildCount(); c < max; c++) {
SpelNode child = getChild(c);
if (!(child instanceof Literal)) {
if (child instanceof InlineList) {
InlineList inlineList = (InlineList) child;
if (!inlineList.isConstant()) {
isConstant = false;
}
}
else {
isConstant = false;
}
}
}
if (isConstant) {
List<Object> constantList = new ArrayList<>();
int childcount = getChildCount();
for (int c = 0; c < childcount; c++) {
SpelNode child = getChild(c);
if ((child instanceof Literal)) {
constantList.add(((Literal) child).getLiteralValue().getValue());
}
else if (child instanceof InlineList) {
constantList.add(((InlineList) child).getConstantValue());
}
}
this.constant = new TypedValue(Collections.unmodifiableList(constantList));
}
}
@Override
public TypedValue getValueInternal(ExpressionState expressionState) throws EvaluationException {
if (this.constant != null) {
return this.constant;
}
else {
List<Object> returnValue = new ArrayList<>();
int childCount = getChildCount();
for (int c = 0; c < childCount; c++) {
returnValue.add(getChild(c).getValue(expressionState));
}
return new TypedValue(returnValue);
}
}
@Override
public String toStringAST() {
StringBuilder sb = new StringBuilder("{");
// String ast matches input string, not the 'toString()' of the resultant collection, which would use []
int count = getChildCount();
for (int c = 0; c < count; c++) {
if (c > 0) {
sb.append(",");
}
sb.append(getChild(c).toStringAST());
}
sb.append("}");
return sb.toString();
}
/**
* Return whether this list is a constant value.
*/
public boolean isConstant() {
return (this.constant != null);
}
@SuppressWarnings("unchecked")
public List<Object> getConstantValue() {
return (List<Object>) this.constant.getValue();
}
@Override
public boolean isCompilable() {
return isConstant();
}
@Override
public void generateCode(MethodVisitor mv, CodeFlow codeflow) {
final String constantFieldName = "inlineList$" + codeflow.nextFieldId();
final String className = codeflow.getClassName();
codeflow.registerNewField(new CodeFlow.FieldAdder() {
public void generateField(ClassWriter cw, CodeFlow codeflow) {
cw.visitField(ACC_PRIVATE|ACC_STATIC|ACC_FINAL, constantFieldName, "Ljava/util/List;", null, null);
}
});
codeflow.registerNewClinit(new CodeFlow.ClinitAdder() {
public void generateCode(MethodVisitor mv, CodeFlow codeflow) {
generateClinitCode(className, constantFieldName, mv, codeflow, false);
}
});
mv.visitFieldInsn(GETSTATIC, className, constantFieldName, "Ljava/util/List;");
codeflow.pushDescriptor("Ljava/util/List");
}
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);
}
}
}