ReflectiveField.java
/*
* Copyright (C) 2021 The Android Open Source Project
*
* 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
*
* http://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 androidx.test.internal.platform.reflect;
import androidx.annotation.RestrictTo;
import androidx.annotation.RestrictTo.Scope;
import java.lang.reflect.Field;
/**
* Helper class for making more performant reflection field access.
*
* <p>Lazy initializes and caches Method object ro attempt to reduce reflection overhead.
*
* @hide
*/
@RestrictTo(Scope.LIBRARY_GROUP)
public class ReflectiveField<T> {
private final String className;
private final String fieldName;
// lazy init
private boolean initialized = false;
private Field field;
/**
* Creates a ReflectiveField.
*
* @param className the fully qualified class name that defines the field
* @param fieldName the field name
*/
public ReflectiveField(String className, String fieldName) {
this.className = className;
this.fieldName = fieldName;
}
/**
* Retrieves the field's value, initializing if necessary.
*
* @param object the object that holds the field's value
* @return the field's value
* @throws ReflectionException if field could not be accessed
*/
public T get(Object object) throws ReflectionException {
try {
initIfNecessary();
return (T) field.get(object);
} catch (ClassNotFoundException | IllegalAccessException | NoSuchFieldException e) {
throw new ReflectionException(e);
}
}
private synchronized void initIfNecessary() throws ClassNotFoundException, NoSuchFieldException {
if (initialized) {
return;
}
field = Class.forName(className).getDeclaredField(fieldName);
field.setAccessible(true);
initialized = true;
}
}