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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; import org.springframework.core.convert.TypeDescriptor; import org.springframework.lang.Nullable; /** * An expression capable of evaluating itself against context objects. * Encapsulates the details of a previously parsed expression string. * Provides a common abstraction for expression evaluation. * * @author Keith Donald * @author Andy Clement * @author Juergen Hoeller * @since 3.0 */ public interface Expression { /** * Return the original string used to create this expression (unmodified). * @return the original expression string */ String getExpressionString(); /** * Evaluate this expression in the default standard context. * @return the evaluation result * @throws EvaluationException if there is a problem during evaluation */ @Nullable Object getValue() throws EvaluationException; /** * Evaluate the expression in the default context. If the result * of the evaluation does not match (and cannot be converted to) * the expected result type then an exception will be returned. * @param desiredResultType the class the caller would like the result to be * @return the evaluation result * @throws EvaluationException if there is a problem during evaluation */ @Nullable <T> T getValue(@Nullable Class<T> desiredResultType) throws EvaluationException; /** * Evaluate this expression against the specified root object. * @param rootObject the root object against which to evaluate the expression * @return the evaluation result * @throws EvaluationException if there is a problem during evaluation */ @Nullable Object getValue(Object rootObject) throws EvaluationException; /** * Evaluate the expression in the default context against the specified root * object. If the result of the evaluation does not match (and cannot be * converted to) the expected result type then an exception will be returned. * @param rootObject the root object against which to evaluate the expression * @param desiredResultType the class the caller would like the result to be * @return the evaluation result * @throws EvaluationException if there is a problem during evaluation */ @Nullable <T> T getValue(Object rootObject, @Nullable Class<T> desiredResultType) throws EvaluationException; /** * Evaluate this expression in the provided context and return the result * of evaluation. * @param context the context in which to evaluate the expression * @return the evaluation result * @throws EvaluationException if there is a problem during evaluation */ @Nullable Object getValue(EvaluationContext context) throws EvaluationException; /** * Evaluate this expression in the provided context and return the result * of evaluation, but use the supplied root context as an override for any * default root object specified in the context. * @param context the context in which to evaluate the expression * @param rootObject the root object against which to evaluate the expression * @return the evaluation result * @throws EvaluationException if there is a problem during evaluation */ @Nullable Object getValue(EvaluationContext context, Object rootObject) throws EvaluationException; /** * Evaluate the expression in a specified context which can resolve references * to properties, methods, types, etc. The type of the evaluation result is * expected to be of a particular class and an exception will be thrown if it * is not and cannot be converted to that type. * @param context the context in which to evaluate the expression * @param desiredResultType the class the caller would like the result to be * @return the evaluation result * @throws EvaluationException if there is a problem during evaluation */ @Nullable <T> T getValue(EvaluationContext context, @Nullable Class<T> desiredResultType) throws EvaluationException; /** * Evaluate the expression in a specified context which can resolve references * to properties, methods, types, etc. The type of the evaluation result is * expected to be of a particular class and an exception will be thrown if it * is not and cannot be converted to that type. The supplied root object * overrides any default specified on the supplied context. * @param context the context in which to evaluate the expression * @param rootObject the root object against which to evaluate the expression * @param desiredResultType the class the caller would like the result to be * @return the evaluation result * @throws EvaluationException if there is a problem during evaluation */ @Nullable <T> T getValue(EvaluationContext context, Object rootObject, @Nullable Class<T> desiredResultType) throws EvaluationException; /** * Return the most general type that can be passed to a {@link #setValue} * method using the default context. * @return the most general type of value that can be set on this context * @throws EvaluationException if there is a problem determining the type */ @Nullable Class<?> getValueType() throws EvaluationException; /** * Return the most general type that can be passed to the * {@link #setValue(Object, Object)} method using the default context. * @param rootObject the root object against which to evaluate the expression * @return the most general type of value that can be set on this context * @throws EvaluationException if there is a problem determining the type */ @Nullable Class<?> getValueType(Object rootObject) throws EvaluationException; /** * Return the most general type that can be passed to the * {@link #setValue(EvaluationContext, Object)} method for the given context. * @param context the context in which to evaluate the expression * @return the most general type of value that can be set on this context * @throws EvaluationException if there is a problem determining the type */ @Nullable Class<?> getValueType(EvaluationContext context) throws EvaluationException; /** * Return the most general type that can be passed to the * {@link #setValue(EvaluationContext, Object, Object)} method for the given * context. The supplied root object overrides any specified in the context. * @param context the context in which to evaluate the expression * @param rootObject the root object against which to evaluate the expression * @return the most general type of value that can be set on this context * @throws EvaluationException if there is a problem determining the type */ @Nullable Class<?> getValueType(EvaluationContext context, Object rootObject) throws EvaluationException; /** * Return the most general type that can be passed to a {@link #setValue} * method using the default context. * @return a type descriptor for values that can be set on this context * @throws EvaluationException if there is a problem determining the type */ @Nullable TypeDescriptor getValueTypeDescriptor() throws EvaluationException; /** * Return the most general type that can be passed to the * {@link #setValue(Object, Object)} method using the default context. * @param rootObject the root object against which to evaluate the expression * @return a type descriptor for values that can be set on this context * @throws EvaluationException if there is a problem determining the type */ @Nullable TypeDescriptor getValueTypeDescriptor(Object rootObject) throws EvaluationException; /** * Return the most general type that can be passed to the * {@link #setValue(EvaluationContext, Object)} method for the given context. * @param context the context in which to evaluate the expression * @return a type descriptor for values that can be set on this context * @throws EvaluationException if there is a problem determining the type */ @Nullable TypeDescriptor getValueTypeDescriptor(EvaluationContext context) throws EvaluationException; /** * Return the most general type that can be passed to the * {@link #setValue(EvaluationContext, Object, Object)} method for the given * context. The supplied root object overrides any specified in the context. * @param context the context in which to evaluate the expression * @param rootObject the root object against which to evaluate the expression * @return a type descriptor for values that can be set on this context * @throws EvaluationException if there is a problem determining the type */ @Nullable TypeDescriptor getValueTypeDescriptor(EvaluationContext context, Object rootObject) throws EvaluationException; /** * Determine if an expression can be written to, i.e. setValue() can be called. * @param rootObject the root object against which to evaluate the expression * @return {@code true} if the expression is writable; {@code false} otherwise * @throws EvaluationException if there is a problem determining if it is writable */ boolean isWritable(Object rootObject) throws EvaluationException; /** * Determine if an expression can be written to, i.e. setValue() can be called. * @param context the context in which the expression should be checked * @return {@code true} if the expression is writable; {@code false} otherwise * @throws EvaluationException if there is a problem determining if it is writable */ boolean isWritable(EvaluationContext context) throws EvaluationException; /** * Determine if an expression can be written to, i.e. setValue() can be called. * The supplied root object overrides any specified in the context. * @param context the context in which the expression should be checked * @param rootObject the root object against which to evaluate the expression * @return {@code true} if the expression is writable; {@code false} otherwise * @throws EvaluationException if there is a problem determining if it is writable */ boolean isWritable(EvaluationContext context, Object rootObject) throws EvaluationException; /** * Set this expression in the provided context to the value provided. * @param rootObject the root object against which to evaluate the expression * @param value the new value * @throws EvaluationException if there is a problem during evaluation */ void setValue(Object rootObject, @Nullable Object value) throws EvaluationException; /** * Set this expression in the provided context to the value provided. * @param context the context in which to set the value of the expression * @param value the new value * @throws EvaluationException if there is a problem during evaluation */ void setValue(EvaluationContext context, @Nullable Object value) throws EvaluationException; /** * Set this expression in the provided context to the value provided. * The supplied root object overrides any specified in the context. * @param context the context in which to set the value of the expression * @param rootObject the root object against which to evaluate the expression * @param value the new value * @throws EvaluationException if there is a problem during evaluation */ void setValue(EvaluationContext context, Object rootObject, @Nullable Object value) throws EvaluationException; }