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Java Annotation Command Interface
/******************************************************************************
* Copyright (C) 2016 Yevgeny Krasik *
* *
* 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 com.github.ykrasik.jaci.reflection;
import com.github.ykrasik.jaci.util.function.Spplr;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
/**
* Suppliers that supply through reflection, usually by invoking a method.
*
* @author Yevgeny Krasik
*/
public final class ReflectionSuppliers {
private ReflectionSuppliers() { }
/**
* Create a supplier that will invoke the method specified by the give method name
* on the given object instance through reflection.
* The method must be no-args and must return a value of the specified type.
* The method may be private, in which case it will be made accessible outside it's class.
*
* @param instance Instance to invoke the method one.
* @param methodName Method name to invoke. Method must be no-args and return a value of the specified type.
* @param suppliedClass Expected return type of the method.
* @param Supplier return type.
* @return A {@link Spplr} that will invoke the no-args method specified by the given name on the given instance.
*/
public static Spplr reflectionSupplier(Object instance,
String methodName,
Class suppliedClass) {
final ReflectionMethod method = ReflectionUtils.getNoArgsMethod(instance.getClass(), methodName);
ReflectionUtils.assertReturnValue(method, suppliedClass);
return new ReflectionSupplier<>(instance, method);
}
/**
* Similar to {@link #reflectionSupplier(Object, String, Class)}, except allows for an alternative return type.
* Will first try to create a reflection supplier using the primary class, but if that fails (the method doesn't
* return the primary class), will re-try with the secondary class.
* Useful for cases where the return type could be either a primitive or the primitive's boxed version
* (i.e. Integer.type or Integer.class).
*
* @param instance Instance to invoke the method one.
* @param methodName Method name to invoke. Method must be no-args and return a value of
* either the primary class or the secondary type.
* @param primaryClass Primary return type of the method. Will be tried first.
* @param secondaryClass Secondary return type of the method.
* Will be tried if the method doesn't return the primary type.
* @param Supplier return type.
* @return A {@link Spplr} that will invoke the no-args method specified by the given name on the given instance.
*/
public static Spplr reflectionSupplier(Object instance,
String methodName,
Class primaryClass,
Class secondaryClass) {
try {
return reflectionSupplier(instance, methodName, primaryClass);
} catch (IllegalArgumentException e) {
// Try the alternative return value.
return reflectionSupplier(instance, methodName, secondaryClass);
}
}
/**
* A {@link Spplr} that invokes a (possibly private) no-args method through reflection.
*
* @author Yevgeny Krasik
*/
private static class ReflectionSupplier implements Spplr {
private final Object instance;
private final ReflectionMethod method;
private ReflectionSupplier(Object instance, ReflectionMethod method) {
this.instance = Objects.requireNonNull(instance, "instance");
this.method = Objects.requireNonNull(method, "method");
}
@Override
public T get() {
return ReflectionUtils.invokeNoArgs(instance, method);
}
@Override
public String toString() {
final StringBuilder sb = new StringBuilder("ReflectionSupplier{");
sb.append("instance=").append(instance);
sb.append(", method=").append(method);
sb.append('}');
return sb.toString();
}
}
/**
* Create a supplier that will invoke the method specified by the give method name
* on the given object instance through reflection.
* The created supplier will supply a {@link List} of values.
* The method must be no-args and must return an array of the specified type.
* The method may be private, in which case it will be made accessible outside it's class.
*
* @param instance Instance to invoke the method one.
* @param methodName Method name to invoke. Method must be no-args and return an array of the specified type.
* @param suppliedClass Expected array return type of the method.
* @param Supplier return type.
* @return A {@link Spplr} that will invoke the no-args method specified by the given name on the given instance.
*/
public static Spplr> reflectionListSupplier(Object instance, String methodName, Class suppliedClass) {
final Spplr supplier = reflectionSupplier(instance, methodName, suppliedClass);
return new ArrayListSupplier<>(supplier);
}
/**
* A {@link Spplr} that wraps another {@link Spplr} that returns an array of {@code T}, delegates to that supplier
* and instead wraps the returned array in a {@link List} of {@code T}.
*
* @author Yevgeny Krasik
*/
private static class ArrayListSupplier implements Spplr> {
private final Spplr supplier;
private ArrayListSupplier(Spplr supplier) {
this.supplier = Objects.requireNonNull(supplier);
}
@Override
public List get() {
return Arrays.asList(supplier.get());
}
@Override
public String toString() {
final StringBuilder sb = new StringBuilder("ReflectionListSupplier{");
sb.append("supplier=").append(supplier);
sb.append('}');
return sb.toString();
}
}
}
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