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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.context.expression; import java.util.Map; import org.springframework.asm.MethodVisitor; import org.springframework.expression.AccessException; import org.springframework.expression.EvaluationContext; import org.springframework.expression.TypedValue; import org.springframework.expression.spel.CodeFlow; import org.springframework.expression.spel.CompilablePropertyAccessor; import org.springframework.lang.Nullable; import org.springframework.util.Assert; /** * EL property accessor that knows how to traverse the keys * of a standard {@link java.util.Map}. * * @author Juergen Hoeller * @author Andy Clement * @since 3.0 */ public class MapAccessor implements CompilablePropertyAccessor { @Override public Class<?>[] getSpecificTargetClasses() { return new Class<?>[] { Map.class }; } @Override public boolean canRead(EvaluationContext context, @Nullable Object target, String name) throws AccessException { return (target instanceof Map && ((Map<?, ?>) target).containsKey(name)); } @Override public TypedValue read(EvaluationContext context, @Nullable Object target, String name) throws AccessException { Assert.state(target instanceof Map, "Target must be of type Map"); Map<?, ?> map = (Map<?, ?>) target; Object value = map.get(name); if (value == null && !map.containsKey(name)) { throw new MapAccessException(name); } return new TypedValue(value); } @Override public boolean canWrite(EvaluationContext context, @Nullable Object target, String name) throws AccessException { return true; } @Override @SuppressWarnings("unchecked") public void write(EvaluationContext context, @Nullable Object target, String name, @Nullable Object newValue) throws AccessException { Assert.state(target instanceof Map, "Target must be a Map"); Map<Object, Object> map = (Map<Object, Object>) target; map.put(name, newValue); } @Override public boolean isCompilable() { return true; } @Override public Class<?> getPropertyType() { return Object.class; } @Override public void generateCode(String propertyName, MethodVisitor mv, CodeFlow cf) { String descriptor = cf.lastDescriptor(); if (descriptor == null || !descriptor.equals("Ljava/util/Map")) { if (descriptor == null) { cf.loadTarget(mv); } CodeFlow.insertCheckCast(mv, "Ljava/util/Map"); } mv.visitLdcInsn(propertyName); mv.visitMethodInsn(INVOKEINTERFACE, "java/util/Map", "get", "(Ljava/lang/Object;)Ljava/lang/Object;", true); } /** * Exception thrown from {@code read} in order to reset a cached * PropertyAccessor, allowing other accessors to have a try. */ @SuppressWarnings("serial") private static class MapAccessException extends AccessException { private final String key; public MapAccessException(String key) { super(""); this.key = key; } @Override public String getMessage() { return "Map does not contain a value for key '" + this.key + "'"; } } }