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Spring Framework example source code file (MethodParameter.java)

This example Spring Framework source code file (MethodParameter.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, constructor, constructor, illegalargumentexception, integer, map, method, method, methodparameter, methodparameter, object, object, parameternamediscoverer, reflection, string, util

The Spring Framework MethodParameter.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.core;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils;

/**
 * Helper class that encapsulates the specification of a method parameter, i.e.
 * a Method or Constructor plus a parameter index and a nested type index for
 * a declared generic type. Useful as a specification object to pass along.
 *
 * <p>Used by {@link GenericCollectionTypeResolver},
 * {@link org.springframework.beans.BeanWrapperImpl} and
 * {@link org.springframework.beans.factory.support.AbstractBeanFactory}.
 *
 * <p>Note that this class does not depend on JDK 1.5 API artifacts, in order
 * to remain compatible with JDK 1.4. Concrete generic type resolution
 * via JDK 1.5 API happens in {@link GenericCollectionTypeResolver} only.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @since 2.0
 * @see GenericCollectionTypeResolver
 */
public class MethodParameter {

	private static final Method methodParameterAnnotationsMethod =
			ClassUtils.getMethodIfAvailable(Method.class, "getParameterAnnotations", new Class[0]);

	private static final Method constructorParameterAnnotationsMethod =
			ClassUtils.getMethodIfAvailable(Constructor.class, "getParameterAnnotations", new Class[0]);


	private Method method;

	private Constructor constructor;

	private final int parameterIndex;

	private Class parameterType;

	private Object[] parameterAnnotations;

	private ParameterNameDiscoverer parameterNameDiscoverer;

	private String parameterName;

	private int nestingLevel = 1;

	/** Map from Integer level to Integer type index */
	private Map typeIndexesPerLevel;

	Map typeVariableMap;


	/**
	 * Create a new MethodParameter for the given method, with nesting level 1.
	 * @param method the Method to specify a parameter for
	 * @param parameterIndex the index of the parameter
	 */
	public MethodParameter(Method method, int parameterIndex) {
		this(method, parameterIndex, 1);
	}

	/**
	 * Create a new MethodParameter for the given method.
	 * @param method the Method to specify a parameter for
	 * @param parameterIndex the index of the parameter
	 * (-1 for the method return type; 0 for the first method parameter,
	 * 1 for the second method parameter, etc)
	 * @param nestingLevel the nesting level of the target type
	 * (typically 1; e.g. in case of a List of Lists, 1 would indicate the
	 * nested List, whereas 2 would indicate the element of the nested List)
	 */
	public MethodParameter(Method method, int parameterIndex, int nestingLevel) {
		Assert.notNull(method, "Method must not be null");
		this.method = method;
		this.parameterIndex = parameterIndex;
		this.nestingLevel = nestingLevel;
	}

	/**
	 * Create a new MethodParameter for the given constructor, with nesting level 1.
	 * @param constructor the Constructor to specify a parameter for
	 * @param parameterIndex the index of the parameter
	 */
	public MethodParameter(Constructor constructor, int parameterIndex) {
		this(constructor, parameterIndex, 1);
	}

	/**
	 * Create a new MethodParameter for the given constructor.
	 * @param constructor the Constructor to specify a parameter for
	 * @param parameterIndex the index of the parameter
	 * @param nestingLevel the nesting level of the target type
	 * (typically 1; e.g. in case of a List of Lists, 1 would indicate the
	 * nested List, whereas 2 would indicate the element of the nested List)
	 */
	public MethodParameter(Constructor constructor, int parameterIndex, int nestingLevel) {
		Assert.notNull(constructor, "Constructor must not be null");
		this.constructor = constructor;
		this.parameterIndex = parameterIndex;
		this.nestingLevel = nestingLevel;
	}

	/**
	 * Copy constructor, resulting in an independent MethodParameter object
	 * based on the same metadata and cache state that the original object was in.
	 * @param original the original MethodParameter object to copy from
	 */
	public MethodParameter(MethodParameter original) {
		Assert.notNull(original, "Original must not be null");
		this.method = original.method;
		this.constructor = original.constructor;
		this.parameterIndex = original.parameterIndex;
		this.parameterType = original.parameterType;
		this.parameterAnnotations = original.parameterAnnotations;
		this.typeVariableMap = original.typeVariableMap;
	}


	/**
	 * Return the wrapped Method, if any.
	 * <p>Note: Either Method or Constructor is available.
	 * @return the Method, or <code>null if none
	 */
	public Method getMethod() {
		return this.method;
	}

	/**
	 * Return the wrapped Constructor, if any.
	 * <p>Note: Either Method or Constructor is available.
	 * @return the Constructor, or <code>null if none
	 */
	public Constructor getConstructor() {
		return this.constructor;
	}

	/**
	 * Return the index of the method/constructor parameter.
	 * @return the parameter index (never negative)
	 */
	public int getParameterIndex() {
		return this.parameterIndex;
	}

	/**
	 * Set a resolved (generic) parameter type.
	 */
	void setParameterType(Class parameterType) {
		this.parameterType = parameterType;
	}

	/**
	 * Return the type of the method/constructor parameter.
	 * @return the parameter type (never <code>null)
	 */
	public Class getParameterType() {
		if (this.parameterType == null) {
			this.parameterType = (this.method != null ?
					this.method.getParameterTypes()[this.parameterIndex] :
					this.constructor.getParameterTypes()[this.parameterIndex]);
		}
		return this.parameterType;
	}

	/**
	 * Return the annotations associated with the method/constructor parameter.
	 * @return the parameter 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[] getParameterAnnotations() {
		if (this.parameterAnnotations != null) {
			return this.parameterAnnotations;
		}
		if (methodParameterAnnotationsMethod == null) {
			return null;
		}
		Object[][] annotationArray = (this.method != null ?
				((Object[][]) ReflectionUtils.invokeMethod(methodParameterAnnotationsMethod, this.method)) :
				((Object[][]) ReflectionUtils.invokeMethod(constructorParameterAnnotationsMethod, this.constructor)));
		this.parameterAnnotations = annotationArray[this.parameterIndex];
		return this.parameterAnnotations;
	}

	/**
	 * Initialize parameter name discovery for this method parameter.
	 * <p>This method does not actually try to retrieve the parameter name at
	 * this point; it just allows discovery to happen when the application calls
	 * {@link #getParameterName()} (if ever).
	 */
	public void initParameterNameDiscovery(ParameterNameDiscoverer parameterNameDiscoverer) {
		this.parameterNameDiscoverer = parameterNameDiscoverer;
	}

	/**
	 * Return the name of the method/constructor parameter.
	 * @return the parameter name (may be <code>null if no
	 * parameter name metadata is contained in the class file or no
	 * {@link #initParameterNameDiscovery ParameterNameDiscoverer}
	 * has been set to begin with)
	 */
	public String getParameterName() {
		if (this.parameterNameDiscoverer != null) {
			String[] parameterNames = (this.method != null ?
					this.parameterNameDiscoverer.getParameterNames(this.method) :
					this.parameterNameDiscoverer.getParameterNames(this.constructor));
			if (parameterNames != null) {
				this.parameterName = parameterNames[this.parameterIndex];
			}
			this.parameterNameDiscoverer = null;
		}
		return this.parameterName;
	}

	/**
	 * Increase this parameter's nesting level.
	 * @see #getNestingLevel()
	 */
	public void increaseNestingLevel() {
		this.nestingLevel++;
	}

	/**
	 * Decrease this parameter's nesting level.
	 * @see #getNestingLevel()
	 */
	public void decreaseNestingLevel() {
		getTypeIndexesPerLevel().remove(new Integer(this.nestingLevel));
		this.nestingLevel--;
	}

	/**
	 * Return the nesting level of the target type
	 * (typically 1; e.g. in case of a List of Lists, 1 would indicate the
	 * nested List, whereas 2 would indicate the element of the nested List).
	 */
	public int getNestingLevel() {
		return this.nestingLevel;
	}

	/**
	 * Set the type index for the current nesting level.
	 * @param typeIndex the corresponding type index
	 * (or <code>null for the default type index)
	 * @see #getNestingLevel()
	 */
	public void setTypeIndexForCurrentLevel(int typeIndex) {
		getTypeIndexesPerLevel().put(new Integer(this.nestingLevel), new Integer(typeIndex));
	}

	/**
	 * Return the type index for the current nesting level.
	 * @return the corresponding type index, or <code>null
	 * if none specified (indicating the default type index)
	 * @see #getNestingLevel()
	 */
	public Integer getTypeIndexForCurrentLevel() {
		return getTypeIndexForLevel(this.nestingLevel);
	}

	/**
	 * Return the type index for the specified nesting level.
	 * @param nestingLevel the nesting level to check
	 * @return the corresponding type index, or <code>null
	 * if none specified (indicating the default type index)
	 */
	public Integer getTypeIndexForLevel(int nestingLevel) {
		return (Integer) getTypeIndexesPerLevel().get(new Integer(nestingLevel));
	}

	/**
	 * Obtain the (lazily constructed) type-indexes-per-level Map.
	 */
	private Map getTypeIndexesPerLevel() {
		if (this.typeIndexesPerLevel == null) {
			this.typeIndexesPerLevel = new HashMap(4);
		}
		return this.typeIndexesPerLevel;
	}


	/**
	 * Create a new MethodParameter for the given method or constructor.
	 * <p>This is a convenience constructor for scenarios where a
	 * Method or Constructor reference is treated in a generic fashion.
	 * @param methodOrConstructor the Method or Constructor to specify a parameter for
	 * @param parameterIndex the index of the parameter
	 * @return the corresponding MethodParameter instance
	 */
	public static MethodParameter forMethodOrConstructor(Object methodOrConstructor, int parameterIndex) {
		if (methodOrConstructor instanceof Method) {
			return new MethodParameter((Method) methodOrConstructor, parameterIndex);
		}
		else if (methodOrConstructor instanceof Constructor) {
			return new MethodParameter((Constructor) methodOrConstructor, parameterIndex);
		}
		else {
			throw new IllegalArgumentException(
					"Given object [" + methodOrConstructor + "] is neither a Method nor a Constructor");
		}
	}

}

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