001/* 002 * Copyright 2002-2017 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.context.expression; 018 019import org.springframework.core.env.Environment; 020import org.springframework.expression.AccessException; 021import org.springframework.expression.EvaluationContext; 022import org.springframework.expression.PropertyAccessor; 023import org.springframework.expression.TypedValue; 024import org.springframework.lang.Nullable; 025import org.springframework.util.Assert; 026 027/** 028 * Read-only EL property accessor that knows how to retrieve keys 029 * of a Spring {@link Environment} instance. 030 * 031 * @author Chris Beams 032 * @since 3.1 033 */ 034public class EnvironmentAccessor implements PropertyAccessor { 035 036 @Override 037 public Class<?>[] getSpecificTargetClasses() { 038 return new Class<?>[] {Environment.class}; 039 } 040 041 /** 042 * Can read any {@link Environment}, thus always returns true. 043 * @return true 044 */ 045 @Override 046 public boolean canRead(EvaluationContext context, @Nullable Object target, String name) throws AccessException { 047 return true; 048 } 049 050 /** 051 * Access the given target object by resolving the given property name against the given target 052 * environment. 053 */ 054 @Override 055 public TypedValue read(EvaluationContext context, @Nullable Object target, String name) throws AccessException { 056 Assert.state(target instanceof Environment, "Target must be of type Environment"); 057 return new TypedValue(((Environment) target).getProperty(name)); 058 } 059 060 /** 061 * Read-only: returns {@code false}. 062 */ 063 @Override 064 public boolean canWrite(EvaluationContext context, @Nullable Object target, String name) throws AccessException { 065 return false; 066 } 067 068 /** 069 * Read-only: no-op. 070 */ 071 @Override 072 public void write(EvaluationContext context, @Nullable Object target, String name, @Nullable Object newValue) 073 throws AccessException { 074 } 075 076}