com.jfinal.template.expr.ast.ExprList Maven / Gradle / Ivy
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the jfinal enjoy plugin for normal java program to use sql management function.
/**
* Copyright (c) 2011-2017, James Zhan 詹波 ([email protected]).
*
* 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 com.jfinal.template.expr.ast;
import java.util.ArrayList;
import java.util.List;
import com.jfinal.template.TemplateException;
import com.jfinal.template.stat.Scope;
/**
* ExprList
*/
public class ExprList extends Expr {
public static final Expr NULL_EXPR = NullExpr.me;
public static final Expr[] NULL_EXPR_ARRAY = new Expr[0];
public static final ExprList NULL_EXPR_LIST = new ExprList(new ArrayList(0));
public static final Object[] NULL_OBJECT_ARRAY = new Object[0];
private Expr[] exprArray;
public ExprList(List exprList) {
if (exprList.size() > 0) {
exprArray = exprList.toArray(new Expr[exprList.size()]);
} else {
exprArray = NULL_EXPR_ARRAY;
}
}
/**
* 持有 ExprList 的指令可以通过此方法提升 AST 执行性能
* 1：当 exprArray.length == 1 时返回 exprArray[0]
* 2：当 exprArray.length == 0 时返回 NullExpr
* 3：其它情况返回 ExprList 自身
*
* 意义在于，当满足前面两个条件时，避免掉了 ExprList.eval(...) 方法中的判断与循环
*/
public Expr getActualExpr() {
if (exprArray.length == 1) {
return exprArray[0];
} else if (exprArray.length == 0) {
return NULL_EXPR;
} else {
return this;
}
}
public Expr[] getExprArray() {
return exprArray;
}
public Expr getExpr(int index) {
if (index < 0 || index >= exprArray.length) {
throw new TemplateException("Index out of bounds: index = " + index + ", length = " + exprArray.length, location);
}
return exprArray[index];
}
public Expr getFirstExpr() {
return exprArray.length > 0 ? exprArray[0] : null;
}
public Expr getLastExpr() {
return exprArray.length > 0 ? exprArray[exprArray.length - 1] : null;
}
public int length() {
return exprArray.length;
}
/**
* 对所有表达式求值，只返回最后一个表达式的值
*/
public Object eval(Scope scope) {
// 优化：绝大多数情况下 length 等于 1
if (exprArray.length == 1) {
return exprArray[0].eval(scope);
}
if (exprArray.length == 0) {
return null;
}
int end = exprArray.length - 1;
for (int i=0; i