Spring Framework example source code file (DependencyDescriptor.java)

This example Spring Framework source code file (DependencyDescriptor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

class, class, dependencydescriptor, dependencydescriptor, field, method, methodparameter, methodparameter, object, object, reflection

The Spring Framework DependencyDescriptor.java source code

/*
 * Copyright 2002-2008 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
 *
 *      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 org.springframework.beans.factory.config;

import java.lang.reflect.Field;
import java.lang.reflect.Method;

import org.springframework.core.GenericCollectionTypeResolver;
import org.springframework.core.JdkVersion;
import org.springframework.core.MethodParameter;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils;

/**
 * Descriptor for a specific dependency that is about to be injected.
 * Wraps a constructor parameter, a method parameter or a field,
 * allowing unified access to their metadata.
 *
 * @author Juergen Hoeller
 * @since 2.5
 */
public class DependencyDescriptor {

	private static final Method fieldAnnotationsMethod =
			ClassUtils.getMethodIfAvailable(Field.class, "getAnnotations", new Class[0]);


	private MethodParameter methodParameter;

	private Field field;

	private final boolean required;

	private final boolean eager;

	private Object[] fieldAnnotations;


	/**
	 * Create a new descriptor for a method or constructor parameter.
	 * Considers the dependency as 'eager'.
	 * @param methodParameter the MethodParameter to wrap
	 * @param required whether the dependency is required
	 */
	public DependencyDescriptor(MethodParameter methodParameter, boolean required) {
		this(methodParameter, required, true);
	}

	/**
	 * Create a new descriptor for a method or constructor parameter.
	 * @param methodParameter the MethodParameter to wrap
	 * @param required whether the dependency is required
	 * @param eager whether this dependency is 'eager' in the sense of
	 * eagerly resolving potential target beans for type matching
	 */
	public DependencyDescriptor(MethodParameter methodParameter, boolean required, boolean eager) {
		Assert.notNull(methodParameter, "MethodParameter must not be null");
		this.methodParameter = methodParameter;
		this.required = required;
		this.eager = eager;
	}

	/**
	 * Create a new descriptor for a field.
	 * Considers the dependency as 'eager'.
	 * @param field the field to wrap
	 * @param required whether the dependency is required
	 */
	public DependencyDescriptor(Field field, boolean required) {
		this(field, required, true);
	}

	/**
	 * Create a new descriptor for a field.
	 * @param field the field to wrap
	 * @param required whether the dependency is required
	 * @param eager whether this dependency is 'eager' in the sense of
	 * eagerly resolving potential target beans for type matching
	 */
	public DependencyDescriptor(Field field, boolean required, boolean eager) {
		Assert.notNull(field, "Field must not be null");
		this.field = field;
		this.required = required;
		this.eager = eager;
	}


	/**
	 * Return the wrapped MethodParameter, if any.
	 * <p>Note: Either MethodParameter or Field is available.
	 * @return the MethodParameter, or <code>null if none
	 */
	public MethodParameter getMethodParameter() {
		return this.methodParameter;
	}

	/**
	 * Return the wrapped Field, if any.
	 * <p>Note: Either MethodParameter or Field is available.
	 * @return the Field, or <code>null if none
	 */
	public Field getField() {
		return this.field;
	}

	/**
	 * Return whether this dependency is required.
	 */
	public boolean isRequired() {
		return this.required;
	}

	/**
	 * Return whether this dependency is 'eager' in the sense of
	 * eagerly resolving potential target beans for type matching.
	 */
	public boolean isEager() {
		return this.eager;
	}


	/**
	 * Determine the declared (non-generic) type of the wrapped parameter/field.
	 * @return the declared type (never <code>null)
	 */
	public Class getDependencyType() {
		return (this.field != null ? this.field.getType() : this.methodParameter.getParameterType());
	}

	/**
	 * Determine the generic element type of the wrapped Collection parameter/field, if any.
	 * @return the generic type, or <code>null if none
	 */
	public Class getCollectionType() {
		if (JdkVersion.getMajorJavaVersion() < JdkVersion.JAVA_15) {
			return null;
		}
		return (this.field != null ?
				GenericCollectionTypeResolver.getCollectionFieldType(this.field) :
				GenericCollectionTypeResolver.getCollectionParameterType(this.methodParameter));
	}

	/**
	 * Determine the generic key type of the wrapped Map parameter/field, if any.
	 * @return the generic type, or <code>null if none
	 */
	public Class getMapKeyType() {
		if (JdkVersion.getMajorJavaVersion() < JdkVersion.JAVA_15) {
			return null;
		}
		return (this.field != null ?
				GenericCollectionTypeResolver.getMapKeyFieldType(this.field) :
				GenericCollectionTypeResolver.getMapKeyParameterType(this.methodParameter));
	}

	/**
	 * Determine the generic value type of the wrapped Map parameter/field, if any.
	 * @return the generic type, or <code>null if none
	 */
	public Class getMapValueType() {
		if (JdkVersion.getMajorJavaVersion() < JdkVersion.JAVA_15) {
			return null;
		}
		return (this.field != null ?
				GenericCollectionTypeResolver.getMapValueFieldType(this.field) :
				GenericCollectionTypeResolver.getMapValueParameterType(this.methodParameter));
	}

	/**
	 * Obtain the annotations associated with the wrapped parameter/field, if any.
	 * @return the parameter/field annotations, or <code>null if there is
	 * no annotation support (on JDK < 1.5). The return value is an Object array
	 * instead of an Annotation array simply for compatibility with older JDKs;
	 * feel free to cast it to <code>Annotation[] on JDK 1.5 or higher.
	 */
	public Object[] getAnnotations() {
		if (this.field != null) {
			if (this.fieldAnnotations != null) {
				return this.fieldAnnotations;
			}
			if (fieldAnnotationsMethod == null) {
				return null;
			}
			this.fieldAnnotations = (Object[]) ReflectionUtils.invokeMethod(fieldAnnotationsMethod, this.field);
			return this.fieldAnnotations;
		}
		else {
			return this.methodParameter.getParameterAnnotations();
		}
	}

}