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Apache Commons BeanUtils provides an easy-to-use but flexible wrapper around reflection and introspection.
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.commons.beanutils2;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.io.StreamCorruptedException;
import java.util.List;
import java.util.Map;
import java.util.Objects;
/**
* The metadata describing an individual property of a DynaBean.
*
* The meta contains an optional content type property ({@link #getContentType})
* for use by mapped and iterated properties.
* A mapped or iterated property may choose to indicate the type it expects.
* The DynaBean implementation may choose to enforce this type on its entries.
* Alternatively, an implementation may choose to ignore this property.
* All keys for maps must be of type String so no meta data is needed for map keys.
*
*/
public class DynaProperty implements Serializable {
private static final long serialVersionUID = -3084907613499830175L;
/*
* There are issues with serializing primitive class types on certain JVM versions
* (including java 1.3).
* This class uses a custom serialization implementation that writes an integer
* for these primitive class.
* This list of constants are the ones used in serialization.
* If these values are changed, then older versions will no longer be read correctly
*/
private static final int BOOLEAN_TYPE = 1;
private static final int BYTE_TYPE = 2;
private static final int CHAR_TYPE = 3;
private static final int DOUBLE_TYPE = 4;
private static final int FLOAT_TYPE = 5;
private static final int INT_TYPE = 6;
private static final int LONG_TYPE = 7;
private static final int SHORT_TYPE = 8;
/**
* Constructs a property that accepts any data type.
*
* @param name Name of the property being described
*/
public DynaProperty(final String name) {
this(name, Object.class);
}
/**
* Constructs a property of the specified data type.
*
* @param name Name of the property being described
* @param type Java class representing the property data type
*/
public DynaProperty(final String name, final Class type) {
this.name = name;
this.type = type;
if (type != null && type.isArray()) {
this.contentType = type.getComponentType();
}
}
/**
* Constructs an indexed or mapped {@code DynaProperty} that supports (pseudo)-introspection
* of the content type.
*
* @param name Name of the property being described
* @param type Java class representing the property data type
* @param contentType Class that all indexed or mapped elements are instances of
*/
public DynaProperty(final String name, final Class type, final Class contentType) {
this.name = name;
this.type = type;
this.contentType = contentType;
}
/** Property name */
protected String name;
/**
* Get the name of this property.
* @return the name of the property
*/
public String getName() {
return this.name;
}
/** Property type */
protected transient Class type;
/**
* Gets the Java class representing the data type of the underlying property
* values.
*
* There are issues with serializing primitive class types on certain JVM versions
* (including java 1.3).
* Therefore, this field must not be serialized using the standard methods.
*
* Please leave this field as {@code transient}
*
* @return the property type
*/
public Class getType() {
return this.type;
}
/** The (optional) type of content elements for indexed {@code DynaProperty} */
protected transient Class contentType;
/**
* Empty array.
*/
static final DynaProperty[] EMPTY_DYNA_PROPERTY_ARRAY = new DynaProperty[0];
/**
* Gets the (optional) type of the indexed content for {@code DynaProperty}'s
* that support this feature.
*
* There are issues with serializing primitive class types on certain JVM versions
* (including java 1.3).
* Therefore, this field must not be serialized using the standard methods.
*
* @return the Class for the content type if this is an indexed {@code DynaProperty}
* and this feature is supported. Otherwise null.
*/
public Class getContentType() {
return contentType;
}
/**
* Does this property represent an indexed value (ie an array or List)?
*
* @return {@code true} if the property is indexed (i.e. is a List or
* array), otherwise {@code false}
*/
public boolean isIndexed() {
if (type == null) {
return false;
} else if (type.isArray() || List.class.isAssignableFrom(type)) {
return true;
} else {
return false;
}
}
/**
* Does this property represent a mapped value (ie a Map)?
*
* @return {@code true} if the property is a Map
* otherwise {@code false}
*/
public boolean isMapped() {
if (type == null) {
return false;
}
return Map.class.isAssignableFrom(type);
}
/**
* Checks this instance against the specified Object for equality. Overrides the
* default reference test for equality provided by {@link java.lang.Object#equals(Object)}
* @param obj The object to compare to
* @return {@code true} if object is a dyna property with the same name
* type and content type, otherwise {@code false}
* @since 1.8.0
*/
@Override
public boolean equals(final Object obj) {
boolean result;
result = obj == this;
if (!result && obj instanceof DynaProperty) {
final DynaProperty that = (DynaProperty) obj;
result =
(Objects.equals(this.name, that.name)) &&
(Objects.equals(this.type, that.type)) &&
(Objects.equals(this.contentType, that.contentType));
}
return result;
}
/**
* @return the hashcode for this dyna property
* @see java.lang.Object#hashCode
* @since 1.8.0
*/
@Override
public int hashCode() {
int result = 1;
result = result * 31 + (name == null ? 0 : name.hashCode());
result = result * 31 + (type == null ? 0 : type.hashCode());
result = result * 31 + (contentType == null ? 0 : contentType.hashCode());
return result;
}
/**
* Gets a String representation of this Object.
* @return a String representation of the dyna property
*/
@Override
public String toString() {
final StringBuilder sb = new StringBuilder("DynaProperty[name=");
sb.append(this.name);
sb.append(",type=");
sb.append(this.type);
if (isMapped() || isIndexed()) {
sb.append(" <").append(this.contentType).append(">");
}
sb.append("]");
return sb.toString();
}
/**
* Writes this object safely.
* There are issues with serializing primitive class types on certain JVM versions
* (including java 1.3).
* This method provides a workaround.
*
* @param out {@link ObjectOutputStream} to write object to
* @throws IOException if the object can't be written
*/
private void writeObject(final ObjectOutputStream out) throws IOException {
writeAnyClass(this.type,out);
if (isMapped() || isIndexed()) {
writeAnyClass(this.contentType,out);
}
// write out other values
out.defaultWriteObject();
}
/**
* Write a class using safe encoding to workaround java 1.3 serialization bug.
*/
private void writeAnyClass(final Class clazz, final ObjectOutputStream out) throws IOException {
// safely write out any class
int primitiveType = 0;
if (Boolean.TYPE.equals(clazz)) {
primitiveType = BOOLEAN_TYPE;
} else if (Byte.TYPE.equals(clazz)) {
primitiveType = BYTE_TYPE;
} else if (Character.TYPE.equals(clazz)) {
primitiveType = CHAR_TYPE;
} else if (Double.TYPE.equals(clazz)) {
primitiveType = DOUBLE_TYPE;
} else if (Float.TYPE.equals(clazz)) {
primitiveType = FLOAT_TYPE;
} else if (Integer.TYPE.equals(clazz)) {
primitiveType = INT_TYPE;
} else if (Long.TYPE.equals(clazz)) {
primitiveType = LONG_TYPE;
} else if (Short.TYPE.equals(clazz)) {
primitiveType = SHORT_TYPE;
}
if (primitiveType == 0) {
// then it's not a primitive type
out.writeBoolean(false);
out.writeObject(clazz);
} else {
// we'll write out a constant instead
out.writeBoolean(true);
out.writeInt(primitiveType);
}
}
/**
* Reads field values for this object safely.
* There are issues with serializing primitive class types on certain JVM versions
* (including java 1.3).
* This method provides a workaround.
*
* @param in {@link ObjectInputStream} to read object from
* @throws StreamCorruptedException when the stream data values are outside expected range
* @throws IOException if the input stream can't be read
* @throws ClassNotFoundException When trying to read an object of class that is not on the classpath
*/
private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
this.type = readAnyClass(in);
if (isMapped() || isIndexed()) {
this.contentType = readAnyClass(in);
}
// read other values
in.defaultReadObject();
}
/**
* Reads a class using safe encoding to workaround java 1.3 serialization bug.
*/
private Class readAnyClass(final ObjectInputStream in) throws IOException, ClassNotFoundException {
// read back type class safely
if (in.readBoolean()) {
// it's a type constant
switch (in.readInt()) {
case BOOLEAN_TYPE: return Boolean.TYPE;
case BYTE_TYPE: return Byte.TYPE;
case CHAR_TYPE: return Character.TYPE;
case DOUBLE_TYPE: return Double.TYPE;
case FLOAT_TYPE: return Float.TYPE;
case INT_TYPE: return Integer.TYPE;
case LONG_TYPE: return Long.TYPE;
case SHORT_TYPE: return Short.TYPE;
default:
// something's gone wrong
throw new StreamCorruptedException(
"Invalid primitive type. "
+ "Check version of beanutils used to serialize is compatible.");
}
}
// it's another class
return (Class) in.readObject();
}
}