69 lines
2.0 KiB
Java
69 lines
2.0 KiB
Java
/**
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* Copyright (c) 2011-2017, James Zhan 詹波 (jfinal@126.com).
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.jfinal.template.expr.ast;
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import com.jfinal.template.stat.Ctrl;
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import com.jfinal.template.stat.Location;
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import com.jfinal.template.stat.ParseException;
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import com.jfinal.template.stat.Scope;
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/**
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* NullSafe
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* 在原则上只支持具有动态特征的用法，例如：方法调用、字段取值、Map 与 List 取值
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* 而不支持具有静态特征的用法，例如：static method 调用、shared method 调用
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*
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* 用法：
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* #( seoTitle ?? "JFinal 极速开发社区" )
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* 支持级联： #( a.b.c ?? "JFinal 极速开发社区" )
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* 支持嵌套： #( a ?? b ?? c ?? d)
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*/
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public class NullSafe extends Expr {
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private Expr left;
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private Expr right;
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public NullSafe(Expr left, Expr right, Location location) {
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if (left == null) {
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throw new ParseException("The expression on the left side of null coalescing and safe access operator \"??\" can not be blank", location);
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}
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this.left = left;
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this.right = right;
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this.location = location;
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}
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public Object eval(Scope scope) {
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Ctrl ctrl = scope.getCtrl();
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boolean oldNullSafeValue = ctrl.isNullSafe();
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Object ret;
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try {
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ctrl.setNullSafe(true);
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ret = left.eval(scope);
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} finally {
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ctrl.setNullSafe(oldNullSafeValue);
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}
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return ret == null && right != null ? right.eval(scope) : ret;
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}
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}
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