org.springframework.expression.ParserContext.java Source code

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/*
 * Copyright 2002-2017 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
 *
 *      https://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;

/**
 * Input provided to an expression parser that can influence an expression
 * parsing/compilation routine.
 *
 * @author Keith Donald
 * @author Andy Clement
 * @since 3.0
 */
public interface ParserContext {

    /**
     * Whether or not the expression being parsed is a template. A template expression
     * consists of literal text that can be mixed with evaluatable blocks. Some examples:
     * <pre class="code">
     *       Some literal text
     *     Hello #{name.firstName}!
     *     #{3 + 4}
     * </pre>
     * @return true if the expression is a template, false otherwise
     */
    boolean isTemplate();

    /**
     * For template expressions, returns the prefix that identifies the start of an
     * expression block within a string. For example: "${"
     * @return the prefix that identifies the start of an expression
     */
    String getExpressionPrefix();

    /**
     * For template expressions, return the prefix that identifies the end of an
     * expression block within a string. For example: "}"
     * @return the suffix that identifies the end of an expression
     */
    String getExpressionSuffix();

    /**
     * The default ParserContext implementation that enables template expression
     * parsing mode. The expression prefix is "#{" and the expression suffix is "}".
     * @see #isTemplate()
     */
    ParserContext TEMPLATE_EXPRESSION = new ParserContext() {

        @Override
        public boolean isTemplate() {
            return true;
        }

        @Override
        public String getExpressionPrefix() {
            return "#{";
        }

        @Override
        public String getExpressionSuffix() {
            return "}";
        }
    };

}