/*
* Copyright 2002-2014 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.convert;
import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Type;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import org.springframework.core.MethodParameter;
import org.springframework.core.ResolvableType;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;
/**
* Context about a type to convert from or to.
*
* @author Keith Donald
* @author Andy Clement
* @author Juergen Hoeller
* @author Phillip Webb
* @author Sam Brannen
* @since 3.0
*/
@SuppressWarnings("serial")
public class TypeDescriptor implements Serializable {
static final Annotation[] EMPTY_ANNOTATION_ARRAY = new Annotation[0];
private static final Map<Class<?>, TypeDescriptor> commonTypesCache = new HashMap<Class<?>, TypeDescriptor>(18);
private static final Class<?>[] CACHED_COMMON_TYPES = {
boolean.class, Boolean.class, byte.class, Byte.class, char.class, Character.class,
double.class, Double.class, int.class, Integer.class, long.class, Long.class,
float.class, Float.class, short.class, Short.class, String.class, Object.class};
static {
for (Class<?> preCachedClass : CACHED_COMMON_TYPES) {
commonTypesCache.put(preCachedClass, valueOf(preCachedClass));
}
}
private final Class<?> type;
private final ResolvableType resolvableType;
private final Annotation[] annotations;
/**
* Create a new type descriptor from a {@link MethodParameter}.
* <p>Use this constructor when a source or target conversion point is a
* constructor parameter, method parameter, or method return value.
* @param methodParameter the method parameter
*/
public TypeDescriptor(MethodParameter methodParameter) {
Assert.notNull(methodParameter, "MethodParameter must not be null");
this.resolvableType = ResolvableType.forMethodParameter(methodParameter);
this.type = this.resolvableType.resolve(methodParameter.getParameterType());
this.annotations = (methodParameter.getParameterIndex() == -1 ?
nullSafeAnnotations(methodParameter.getMethodAnnotations()) :
nullSafeAnnotations(methodParameter.getParameterAnnotations()));
}
/**
* Create a new type descriptor from a {@link Field}.
* <p>Use this constructor when a source or target conversion point is a field.
* @param field the field
*/
public TypeDescriptor(Field field) {
Assert.notNull(field, "Field must not be null");
this.resolvableType = ResolvableType.forField(field);
this.type = this.resolvableType.resolve(field.getType());
this.annotations = nullSafeAnnotations(field.getAnnotations());
}
/**
* Create a new type descriptor from a {@link Property}.
* <p>Use this constructor when a source or target conversion point is a
* property on a Java class.
* @param property the property
*/
public TypeDescriptor(Property property) {
Assert.notNull(property, "Property must not be null");
this.resolvableType = ResolvableType.forMethodParameter(property.getMethodParameter());
this.type = this.resolvableType.resolve(property.getType());
this.annotations = nullSafeAnnotations(property.getAnnotations());
}
/**
* Create a new type descriptor from a {@link ResolvableType}. This protected
* constructor is used internally and may also be used by subclasses that support
* non-Java languages with extended type systems.
* @param resolvableType the resolvable type
* @param type the backing type or {@code null} if should be resolved
* @param annotations the type annotations
*/
protected TypeDescriptor(ResolvableType resolvableType, Class<?> type, Annotation[] annotations) {
this.resolvableType = resolvableType;
this.type = (type != null ? type : resolvableType.resolve(Object.class));
this.annotations = nullSafeAnnotations(annotations);
}
private Annotation[] nullSafeAnnotations(Annotation[] annotations) {
return (annotations != null ? annotations : EMPTY_ANNOTATION_ARRAY);
}
/**
* Variation of {@link #getType()} that accounts for a primitive type by
* returning its object wrapper type.
* <p>This is useful for conversion service implementations that wish to
* normalize to object-based types and not work with primitive types directly.
*/
public Class<?> getObjectType() {
return ClassUtils.resolvePrimitiveIfNecessary(getType());
}
/**
* The type of the backing class, method parameter, field, or property
* described by this TypeDescriptor.
* <p>Returns primitive types as-is.
* <p>See {@link #getObjectType()} for a variation of this operation that
* resolves primitive types to their corresponding Object types if necessary.
* @return the type, or {@code null}
* @see #getObjectType()
*/
public Class<?> getType() {
return this.type;
}
/**
* Return the underlying {@link ResolvableType}.
* @since 4.0
*/
public ResolvableType getResolvableType() {
return this.resolvableType;
}
/**
* Return the underlying source of the descriptor. Will return a {@link Field},
* {@link MethodParameter} or {@link Type} depending on how the {@link TypeDescriptor}
* was constructed. This method is primarily to provide access to additional
* type information or meta-data that alternative JVM languages may provide.
* @since 4.0
*/
public Object getSource() {
return (this.resolvableType != null ? this.resolvableType.getSource() : null);
}
/**
* Narrows this {@link TypeDescriptor} by setting its type to the class of the
* provided value.
* <p>If the value is {@code null}, no narrowing is performed and this TypeDescriptor
* is returned unchanged.
* <p>Designed to be called by binding frameworks when they read property, field,
* or method return values. Allows such frameworks to narrow a TypeDescriptor built
* from a declared property, field, or method return value type. For example, a field
* declared as {@code java.lang.Object} would be narrowed to {@code java.util.HashMap}
* if it was set to a {@code java.util.HashMap} value. The narrowed TypeDescriptor
* can then be used to convert the HashMap to some other type. Annotation and nested
* type context is preserved by the narrowed copy.
* @param value the value to use for narrowing this type descriptor
* @return this TypeDescriptor narrowed (returns a copy with its type updated to the
* class of the provided value)
*/
public TypeDescriptor narrow(Object value) {
if (value == null) {
return this;
}
ResolvableType narrowed = ResolvableType.forType(value.getClass(), this.resolvableType);
return new TypeDescriptor(narrowed, null, this.annotations);
}
/**
* Cast this {@link TypeDescriptor} to a superclass or implemented interface
* preserving annotations and nested type context.
* @param superType the super type to cast to (can be {@code null}
* @return a new TypeDescriptor for the up-cast type
* @throws IllegalArgumentException if this type is not assignable to the super-type
* @since 3.2
*/
public TypeDescriptor upcast(Class<?> superType) {
if (superType == null) {
return null;
}
Assert.isAssignable(superType, getType());
return new TypeDescriptor(this.resolvableType.as(superType), superType, this.annotations);
}
/**
* Returns the name of this type: the fully qualified class name.
*/
public String getName() {
return ClassUtils.getQualifiedName(getType());
}
/**
* Is this type a primitive type?
*/
public boolean isPrimitive() {
return getType().isPrimitive();
}
/**
* The annotations associated with this type descriptor, if any.
* @return the annotations, or an empty array if none
*/
public Annotation[] getAnnotations() {
return this.annotations;
}
/**
* Determine if this type descriptor has the specified annotation.
* @param annotationType the annotation type
* @return <tt>true</tt> if the annotation is present
*/
public boolean hasAnnotation(Class<? extends Annotation> annotationType) {
return (getAnnotation(annotationType) != null);
}
/**
* Obtain the annotation associated with this type descriptor of the specified type.
* @param annotationType the annotation type
* @return the annotation, or {@code null} if no such annotation exists on this type descriptor
*/
@SuppressWarnings("unchecked")
public <T extends Annotation> T getAnnotation(Class<T> annotationType) {
for (Annotation annotation : getAnnotations()) {
if (annotation.annotationType().equals(annotationType)) {
return (T) annotation;
}
}
for (Annotation metaAnn : getAnnotations()) {
T ann = metaAnn.annotationType().getAnnotation(annotationType);
if (ann != null) {
return ann;
}
}
return null;
}
/**
* Returns true if an object of this type descriptor can be assigned to the location
* described by the given type descriptor.
* <p>For example, {@code valueOf(String.class).isAssignableTo(valueOf(CharSequence.class))}
* returns {@code true} because a String value can be assigned to a CharSequence variable.
* On the other hand, {@code valueOf(Number.class).isAssignableTo(valueOf(Integer.class))}
* returns {@code false} because, while all Integers are Numbers, not all Numbers are Integers.
* <p>For arrays, collections, and maps, element and key/value types are checked if declared.
* For example, a List<String> field value is assignable to a Collection<CharSequence>
* field, but List<Number> is not assignable to List<Integer>.
* @return {@code true} if this type is assignable to the type represented by the provided
* type descriptor
* @see #getObjectType()
*/
public boolean isAssignableTo(TypeDescriptor typeDescriptor) {
boolean typesAssignable = typeDescriptor.getObjectType().isAssignableFrom(getObjectType());
if (!typesAssignable) {
return false;
}
if (isArray() && typeDescriptor.isArray()) {
return getElementTypeDescriptor().isAssignableTo(typeDescriptor.getElementTypeDescriptor());
}
else if (isCollection() && typeDescriptor.isCollection()) {
return isNestedAssignable(getElementTypeDescriptor(), typeDescriptor.getElementTypeDescriptor());
}
else if (isMap() && typeDescriptor.isMap()) {
return isNestedAssignable(getMapKeyTypeDescriptor(), typeDescriptor.getMapKeyTypeDescriptor()) &&
isNestedAssignable(getMapValueTypeDescriptor(), typeDescriptor.getMapValueTypeDescriptor());
}
else {
return true;
}
}
private boolean isNestedAssignable(TypeDescriptor nestedTypeDescriptor, TypeDescriptor otherNestedTypeDescriptor) {
if (nestedTypeDescriptor == null || otherNestedTypeDescriptor == null) {
return true;
}
return nestedTypeDescriptor.isAssignableTo(otherNestedTypeDescriptor);
}
/**
* Is this type a {@link Collection} type?
*/
public boolean isCollection() {
return Collection.class.isAssignableFrom(getType());
}
/**
* Is this type an array type?
*/
public boolean isArray() {
return getType().isArray();
}
/**
* If this type is an array, returns the array's component type.
* If this type is a {@link Collection} and it is parameterized, returns the Collection's element type.
* If the Collection is not parameterized, returns {@code null} indicating the element type is not declared.
* @return the array component type or Collection element type, or {@code null} if this type is a
* Collection but its element type is not parameterized
* @throws IllegalStateException if this type is not a {@code java.util.Collection} or array type
*/
public TypeDescriptor getElementTypeDescriptor() {
if (this.resolvableType.isArray()) {
return new TypeDescriptor(this.resolvableType.getComponentType(), null, this.annotations);
}
return getRelatedIfResolvable(this, this.resolvableType.asCollection().getGeneric());
}
/**
* If this type is a {@link Collection} or an array, creates a element TypeDescriptor
* from the provided collection or array element.
* <p>Narrows the {@link #getElementTypeDescriptor() elementType} property to the class
* of the provided collection or array element. For example, if this describes a
* {@code java.util.List<java.lang.Number<} and the element argument is an
* {@code java.lang.Integer}, the returned TypeDescriptor will be {@code java.lang.Integer}.
* If this describes a {@code java.util.List<?>} and the element argument is an
* {@code java.lang.Integer}, the returned TypeDescriptor will be {@code java.lang.Integer}
* as well.
* <p>Annotation and nested type context will be preserved in the narrowed
* TypeDescriptor that is returned.
* @param element the collection or array element
* @return a element type descriptor, narrowed to the type of the provided element
* @throws IllegalStateException if this type is not a {@code java.util.Collection}
* or array type
* @see #narrow(Object)
*/
public TypeDescriptor elementTypeDescriptor(Object element) {
return narrow(element, getElementTypeDescriptor());
}
/**
* Is this type a {@link Map} type?
*/
public boolean isMap() {
return Map.class.isAssignableFrom(getType());
}
/**
* If this type is a {@link Map} and its key type is parameterized,
* returns the map's key type. If the Map's key type is not parameterized,
* returns {@code null} indicating the key type is not declared.
* @return the Map key type, or {@code null} if this type is a Map
* but its key type is not parameterized
* @throws IllegalStateException if this type is not a {@code java.util.Map}
*/
public TypeDescriptor getMapKeyTypeDescriptor() {
Assert.state(isMap(), "Not a java.util.Map");
return getRelatedIfResolvable(this, this.resolvableType.asMap().getGeneric(0));
}
/**
* If this type is a {@link Map}, creates a mapKey {@link TypeDescriptor}
* from the provided map key.
* <p>Narrows the {@link #getMapKeyTypeDescriptor() mapKeyType} property
* to the class of the provided map key. For example, if this describes a
* {@code java.util.Map<java.lang.Number, java.lang.String<} and the key
* argument is a {@code java.lang.Integer}, the returned TypeDescriptor will be
* {@code java.lang.Integer}. If this describes a {@code java.util.Map<?, ?>}
* and the key argument is a {@code java.lang.Integer}, the returned
* TypeDescriptor will be {@code java.lang.Integer} as well.
* <p>Annotation and nested type context will be preserved in the narrowed
* TypeDescriptor that is returned.
* @param mapKey the map key
* @return the map key type descriptor
* @throws IllegalStateException if this type is not a {@code java.util.Map}
* @see #narrow(Object)
*/
public TypeDescriptor getMapKeyTypeDescriptor(Object mapKey) {
return narrow(mapKey, getMapKeyTypeDescriptor());
}
/**
* If this type is a {@link Map} and its value type is parameterized,
* returns the map's value type.
* <p>If the Map's value type is not parameterized, returns {@code null}
* indicating the value type is not declared.
* @return the Map value type, or {@code null} if this type is a Map
* but its value type is not parameterized
* @throws IllegalStateException if this type is not a {@code java.util.Map}
*/
public TypeDescriptor getMapValueTypeDescriptor() {
Assert.state(isMap(), "Not a java.util.Map");
return getRelatedIfResolvable(this, this.resolvableType.asMap().getGeneric(1));
}
/**
* If this type is a {@link Map}, creates a mapValue {@link TypeDescriptor}
* from the provided map value.
* <p>Narrows the {@link #getMapValueTypeDescriptor() mapValueType} property
* to the class of the provided map value. For example, if this describes a
* {@code java.util.Map<java.lang.String, java.lang.Number<} and the value
* argument is a {@code java.lang.Integer}, the returned TypeDescriptor will be
* {@code java.lang.Integer}. If this describes a {@code java.util.Map<?, ?>}
* and the value argument is a {@code java.lang.Integer}, the returned
* TypeDescriptor will be {@code java.lang.Integer} as well.
* <p>Annotation and nested type context will be preserved in the narrowed
* TypeDescriptor that is returned.
* @param mapValue the map value
* @return the map value type descriptor
* @throws IllegalStateException if this type is not a {@code java.util.Map}
* @see #narrow(Object)
*/
public TypeDescriptor getMapValueTypeDescriptor(Object mapValue) {
return narrow(mapValue, getMapValueTypeDescriptor());
}
/**
* Returns the value of {@link TypeDescriptor#getType() getType()} for the
* {@link #getElementTypeDescriptor() elementTypeDescriptor}.
* @deprecated in Spring 3.1 in favor of {@link #getElementTypeDescriptor()}
* @throws IllegalStateException if this type is not a {@code java.util.Collection} or array type
*/
@Deprecated
public Class<?> getElementType() {
return getType(getElementTypeDescriptor());
}
/**
* Returns the value of {@link TypeDescriptor#getType() getType()} for the
* {@link #getMapKeyTypeDescriptor() getMapKeyTypeDescriptor}.
* @deprecated in Spring 3.1 in favor of {@link #getMapKeyTypeDescriptor()}
* @throws IllegalStateException if this type is not a {@code java.util.Map}
*/
@Deprecated
public Class<?> getMapKeyType() {
return getType(getMapKeyTypeDescriptor());
}
/**
* Returns the value of {@link TypeDescriptor#getType() getType()} for the
* {@link #getMapValueTypeDescriptor() getMapValueTypeDescriptor}.
* @deprecated in Spring 3.1 in favor of {@link #getMapValueTypeDescriptor()}
* @throws IllegalStateException if this type is not a {@code java.util.Map}
*/
@Deprecated
public Class<?> getMapValueType() {
return getType(getMapValueTypeDescriptor());
}
private Class<?> getType(TypeDescriptor typeDescriptor) {
return (typeDescriptor != null ? typeDescriptor.getType() : null);
}
private TypeDescriptor narrow(Object value, TypeDescriptor typeDescriptor) {
if (typeDescriptor != null) {
return typeDescriptor.narrow(value);
}
return (value != null ? new TypeDescriptor(this.resolvableType, value.getClass(), this.annotations) : null);
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof TypeDescriptor)) {
return false;
}
TypeDescriptor other = (TypeDescriptor) obj;
if (!ObjectUtils.nullSafeEquals(this.type, other.type)) {
return false;
}
if (getAnnotations().length != other.getAnnotations().length) {
return false;
}
for (Annotation ann : getAnnotations()) {
if (other.getAnnotation(ann.annotationType()) == null) {
return false;
}
}
if (isCollection() || isArray()) {
return ObjectUtils.nullSafeEquals(getElementTypeDescriptor(), other.getElementTypeDescriptor());
}
else if (isMap()) {
return ObjectUtils.nullSafeEquals(getMapKeyTypeDescriptor(), other.getMapKeyTypeDescriptor()) &&
ObjectUtils.nullSafeEquals(getMapValueTypeDescriptor(), other.getMapValueTypeDescriptor());
}
else {
return true;
}
}
@Override
public int hashCode() {
return getType().hashCode();
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
for (Annotation ann : getAnnotations()) {
builder.append("@").append(ann.annotationType().getName()).append(' ');
}
builder.append(this.resolvableType.toString());
return builder.toString();
}
/**
* Create a new type descriptor from the given type.
* <p>Use this to instruct the conversion system to convert an object to a
* specific target type, when no type location such as a method parameter or
* field is available to provide additional conversion context.
* <p>Generally prefer use of {@link #forObject(Object)} for constructing type
* descriptors from source objects, as it handles the {@code null} object case.
* @param type the class (may be {@code null} to indicate {@code Object.class})
* @return the corresponding type descriptor
*/
public static TypeDescriptor valueOf(Class<?> type) {
if (type == null) {
type = Object.class;
}
TypeDescriptor desc = commonTypesCache.get(type);
return (desc != null ? desc : new TypeDescriptor(ResolvableType.forClass(type), null, null));
}
/**
* Create a new type descriptor from a {@link java.util.Collection} type.
* <p>Useful for converting to typed Collections.
* <p>For example, a {@code List<String>} could be converted to a
* {@code List<EmailAddress>} by converting to a targetType built with this method.
* The method call to construct such a {@code TypeDescriptor} would look something
* like: {@code collection(List.class, TypeDescriptor.valueOf(EmailAddress.class));}
* @param collectionType the collection type, which must implement {@link Collection}.
* @param elementTypeDescriptor a descriptor for the collection's element type,
* used to convert collection elements
* @return the collection type descriptor
*/
public static TypeDescriptor collection(Class<?> collectionType, TypeDescriptor elementTypeDescriptor) {
Assert.notNull(collectionType, "collectionType must not be null");
if (!Collection.class.isAssignableFrom(collectionType)) {
throw new IllegalArgumentException("collectionType must be a java.util.Collection");
}
ResolvableType element = (elementTypeDescriptor != null ? elementTypeDescriptor.resolvableType : null);
return new TypeDescriptor(ResolvableType.forClassWithGenerics(collectionType, element), null, null);
}
/**
* Create a new type descriptor from a {@link java.util.Map} type.
* <p>Useful for converting to typed Maps.
* <p>For example, a Map<String, String> could be converted to a Map<Id, EmailAddress>
* by converting to a targetType built with this method:
* The method call to construct such a TypeDescriptor would look something like:
* <pre class="code">
* map(Map.class, TypeDescriptor.valueOf(Id.class), TypeDescriptor.valueOf(EmailAddress.class));
* </pre>
* @param mapType the map type, which must implement {@link Map}
* @param keyTypeDescriptor a descriptor for the map's key type, used to convert map keys
* @param valueTypeDescriptor the map's value type, used to convert map values
* @return the map type descriptor
*/
public static TypeDescriptor map(Class<?> mapType, TypeDescriptor keyTypeDescriptor, TypeDescriptor valueTypeDescriptor) {
if (!Map.class.isAssignableFrom(mapType)) {
throw new IllegalArgumentException("mapType must be a java.util.Map");
}
ResolvableType key = (keyTypeDescriptor != null ? keyTypeDescriptor.resolvableType : null);
ResolvableType value = (valueTypeDescriptor != null ? valueTypeDescriptor.resolvableType : null);
return new TypeDescriptor(ResolvableType.forClassWithGenerics(mapType, key, value), null, null);
}
/**
* Create a new type descriptor as an array of the specified type.
* <p>For example to create a {@code Map<String,String>[]} use:
* <pre class="code">
* TypeDescriptor.array(TypeDescriptor.map(Map.class, TypeDescriptor.value(String.class), TypeDescriptor.value(String.class)));
* </pre>
* @param elementTypeDescriptor the {@link TypeDescriptor} of the array element or {@code null}
* @return an array {@link TypeDescriptor} or {@code null} if {@code elementTypeDescriptor} is {@code null}
* @since 3.2.1
*/
public static TypeDescriptor array(TypeDescriptor elementTypeDescriptor) {
if (elementTypeDescriptor == null) {
return null;
}
return new TypeDescriptor(ResolvableType.forArrayComponent(elementTypeDescriptor.resolvableType),
null, elementTypeDescriptor.getAnnotations());
}
/**
* Creates a type descriptor for a nested type declared within the method parameter.
* <p>For example, if the methodParameter is a {@code List<String>} and the
* nesting level is 1, the nested type descriptor will be String.class.
* <p>If the methodParameter is a {@code List<List<String>>} and the nesting
* level is 2, the nested type descriptor will also be a String.class.
* <p>If the methodParameter is a {@code Map<Integer, String>} and the nesting
* level is 1, the nested type descriptor will be String, derived from the map value.
* <p>If the methodParameter is a {@code List<Map<Integer, String>>} and the
* nesting level is 2, the nested type descriptor will be String, derived from the map value.
* <p>Returns {@code null} if a nested type cannot be obtained because it was not declared.
* For example, if the method parameter is a {@code List<?>}, the nested type
* descriptor returned will be {@code null}.
* @param methodParameter the method parameter with a nestingLevel of 1
* @param nestingLevel the nesting level of the collection/array element or
* map key/value declaration within the method parameter
* @return the nested type descriptor at the specified nesting level,
* or {@code null} if it could not be obtained
* @throws IllegalArgumentException if the nesting level of the input
* {@link MethodParameter} argument is not 1, or if the types up to the
* specified nesting level are not of collection, array, or map types
*/
public static TypeDescriptor nested(MethodParameter methodParameter, int nestingLevel) {
if (methodParameter.getNestingLevel() != 1) {
throw new IllegalArgumentException("MethodParameter nesting level must be 1: " +
"use the nestingLevel parameter to specify the desired nestingLevel for nested type traversal");
}
return nested(new TypeDescriptor(methodParameter), nestingLevel);
}
/**
* Creates a type descriptor for a nested type declared within the field.
* <p>For example, if the field is a {@code List<String>} and the nesting
* level is 1, the nested type descriptor will be {@code String.class}.
* <p>If the field is a {@code List<List<String>>} and the nesting level is
* 2, the nested type descriptor will also be a {@code String.class}.
* <p>If the field is a {@code Map<Integer, String>} and the nesting level
* is 1, the nested type descriptor will be String, derived from the map value.
* <p>If the field is a {@code List<Map<Integer, String>>} and the nesting
* level is 2, the nested type descriptor will be String, derived from the map value.
* <p>Returns {@code null} if a nested type cannot be obtained because it was not declared.
* For example, if the field is a {@code List<?>}, the nested type descriptor returned will be {@code null}.
* @param field the field
* @param nestingLevel the nesting level of the collection/array element or
* map key/value declaration within the field
* @return the nested type descriptor at the specified nesting level,
* or {@code null} if it could not be obtained
* @throws IllegalArgumentException if the types up to the specified nesting
* level are not of collection, array, or map types
*/
public static TypeDescriptor nested(Field field, int nestingLevel) {
return nested(new TypeDescriptor(field), nestingLevel);
}
/**
* Creates a type descriptor for a nested type declared within the property.
* <p>For example, if the property is a {@code List<String>} and the nesting
* level is 1, the nested type descriptor will be {@code String.class}.
* <p>If the property is a {@code List<List<String>>} and the nesting level
* is 2, the nested type descriptor will also be a {@code String.class}.
* <p>If the property is a {@code Map<Integer, String>} and the nesting level
* is 1, the nested type descriptor will be String, derived from the map value.
* <p>If the property is a {@code List<Map<Integer, String>>} and the nesting
* level is 2, the nested type descriptor will be String, derived from the map value.
* <p>Returns {@code null} if a nested type cannot be obtained because it was not declared.
* For example, if the property is a {@code List<?>}, the nested type descriptor
* returned will be {@code null}.
* @param property the property
* @param nestingLevel the nesting level of the collection/array element or
* map key/value declaration within the property
* @return the nested type descriptor at the specified nesting level, or
* {@code null} if it could not be obtained
* @throws IllegalArgumentException if the types up to the specified nesting
* level are not of collection, array, or map types
*/
public static TypeDescriptor nested(Property property, int nestingLevel) {
return nested(new TypeDescriptor(property), nestingLevel);
}
/**
* Create a new type descriptor for an object.
* <p>Use this factory method to introspect a source object before asking the
* conversion system to convert it to some another type.
* <p>If the provided object is {@code null}, returns {@code null}, else calls
* {@link #valueOf(Class)} to build a TypeDescriptor from the object's class.
* @param source the source object
* @return the type descriptor
*/
public static TypeDescriptor forObject(Object source) {
return (source != null ? valueOf(source.getClass()) : null);
}
private static TypeDescriptor nested(TypeDescriptor typeDescriptor, int nestingLevel) {
ResolvableType nested = typeDescriptor.resolvableType;
for (int i = 0; i < nestingLevel; i++) {
if (Object.class.equals(nested.getType())) {
// Could be a collection type but we don't know about its element type,
// so let's just assume there is an element type of type Object...
}
else {
nested = nested.getNested(2);
}
}
if (nested == ResolvableType.NONE) {
return null;
}
return getRelatedIfResolvable(typeDescriptor, nested);
}
private static TypeDescriptor getRelatedIfResolvable(TypeDescriptor source, ResolvableType type) {
if (type.resolve() == null) {
return null;
}
return new TypeDescriptor(type, null, source.annotations);
}
}