/*
* @(#)Field.java 1.26 06/10/10
*
* Copyright 1990-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 only, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License version 2 for more details (a copy is
* included at /legal/license.txt).
*
* You should have received a copy of the GNU General Public License
* version 2 along with this work; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.com if you need additional
* information or have any questions.
*
*/
package java.lang.reflect;
/**
* A <code>Field</code> provides information about, and dynamic access to, a
* single field of a class or an interface. The reflected field may
* be a class (static) field or an instance field.
*
* <p>A <code>Field</code> permits widening conversions to occur during a get or
* set access operation, but throws an <code>IllegalArgumentException</code> if a
* narrowing conversion would occur.
*
* @see Member
* @see java.lang.Class
* @see java.lang.Class#getFields()
* @see java.lang.Class#getField(String)
* @see java.lang.Class#getDeclaredFields()
* @see java.lang.Class#getDeclaredField(String)
*
* @author Nakul Saraiya
*/
public final
class Field extends AccessibleObject implements Member {
private Class clazz;
private int slot;
private String name;
private Class type;
private int modifiers;
/**
* Constructor. Only the Java Virtual Machine may construct a Field.
*/
private Field() {}
/**
* Returns the <code>Class</code> object representing the class or interface
* that declares the field represented by this <code>Field</code> object.
*/
public Class getDeclaringClass() {
return clazz;
}
/**
* Returns the name of the field represented by this <code>Field</code> object.
*/
public String getName() {
return name;
}
/**
* Returns the Java language modifiers for the field represented
* by this <code>Field</code> object, as an integer. The <code>Modifier</code> class should
* be used to decode the modifiers.
*
* @see Modifier
*/
public int getModifiers() {
return modifiers;
}
/**
* Returns a <code>Class</code> object that identifies the
* declared type for the field represented by this
* <code>Field</code> object.
*
* @return a <code>Class</code> object identifying the declared
* type of the field represented by this object
*/
public Class getType() {
return type;
}
/**
* Compares this <code>Field</code> against the specified object. Returns
* true if the objects are the same. Two <code>Field</code> objects are the same if
* they were declared by the same class and have the same name
* and type.
*/
public boolean equals(Object obj) {
if (obj != null && obj instanceof Field) {
Field other = (Field)obj;
return (getDeclaringClass() == other.getDeclaringClass())
&& (getName().equals(other.getName()))
&& (getType() == other.getType());
}
return false;
}
/**
* Returns a hashcode for this <code>Field</code>. This is computed as the
* exclusive-or of the hashcodes for the underlying field's
* declaring class name and its name.
*/
public int hashCode() {
return getDeclaringClass().getName().hashCode() ^ getName().hashCode();
}
/**
* Returns a string describing this <code>Field</code>. The format is
* the access modifiers for the field, if any, followed
* by the field type, followed by a space, followed by
* the fully-qualified name of the class declaring the field,
* followed by a period, followed by the name of the field.
* For example:
* <pre>
* public static final int java.lang.Thread.MIN_PRIORITY
* private int java.io.FileDescriptor.fd
* </pre>
*
* <p>The modifiers are placed in canonical order as specified by
* "The Java Language Specification". This is <tt>public</tt>,
* <tt>protected</tt> or <tt>private</tt> first, and then other
* modifiers in the following order: <tt>static</tt>, <tt>final</tt>,
* <tt>transient</tt>, <tt>volatile</tt>.
*/
public String toString() {
int mod = getModifiers();
return (((mod == 0) ? "" : (Modifier.toString(mod) + " "))
+ getTypeName(getType()) + " "
+ getTypeName(getDeclaringClass()) + "."
+ getName());
}
/**
* Returns the value of the field represented by this <code>Field</code>, on
* the specified object. The value is automatically wrapped in an
* object if it has a primitive type.
*
* <p>The underlying field's value is obtained as follows:
*
* <p>If the underlying field is a static field, the <code>obj</code> argument
* is ignored; it may be null.
*
* <p>Otherwise, the underlying field is an instance field. If the
* specified <code>obj</code> argument is null, the method throws a
* <code>NullPointerException.</code> If the specified object is not an
* instance of the class or interface declaring the underlying
* field, the method throws an <code>IllegalArgumentException</code>.
*
* <p>If this <code>Field</code> object enforces Java language access control, and
* the underlying field is inaccessible, the method throws an
* <code>IllegalAccessException</code>.
* If the underlying field is static, the class that declared the
* field is initialized if it has not already been initialized.
*
* <p>Otherwise, the value is retrieved from the underlying instance
* or static field. If the field has a primitive type, the value
* is wrapped in an object before being returned, otherwise it is
* returned as is.
*
* <p>If the field is hidden in the type of <code>obj</code>,
* the field's value is obtained according to the preceding rules.
*
* @param obj object from which the represented field's value is
* to be extracted
* @return the value of the represented field in object
* <tt>obj</tt>; primitive values are wrapped in an appropriate
* object before being returned
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof).
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
*/
public native Object get(Object obj)
throws IllegalArgumentException, IllegalAccessException;
/**
* Gets the value of a static or instance <code>boolean</code> field.
*
* @param obj the object to extract the <code>boolean</code> value
* from
* @return the value of the <code>boolean</code> field
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not
* an instance of the class or interface declaring the
* underlying field (or a subclass or implementor
* thereof), or if the field value cannot be
* converted to the type <code>boolean</code> by a
* widening conversion.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#get
*/
public native boolean getBoolean(Object obj)
throws IllegalArgumentException, IllegalAccessException;
/**
* Gets the value of a static or instance <code>byte</code> field.
*
* @param obj the object to extract the <code>byte</code> value
* from
* @return the value of the <code>byte</code> field
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not
* an instance of the class or interface declaring the
* underlying field (or a subclass or implementor
* thereof), or if the field value cannot be
* converted to the type <code>byte</code> by a
* widening conversion.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#get
*/
public native byte getByte(Object obj)
throws IllegalArgumentException, IllegalAccessException;
/**
* Gets the value of a static or instance field of type
* <code>char</code> or of another primitive type convertible to
* type <code>char</code> via a widening conversion.
*
* @param obj the object to extract the <code>char</code> value
* from
* @return the value of the field converted to type <code>char</code>
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not
* an instance of the class or interface declaring the
* underlying field (or a subclass or implementor
* thereof), or if the field value cannot be
* converted to the type <code>char</code> by a
* widening conversion.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#get
*/
public native char getChar(Object obj)
throws IllegalArgumentException, IllegalAccessException;
/**
* Gets the value of a static or instance field of type
* <code>short</code> or of another primitive type convertible to
* type <code>short</code> via a widening conversion.
*
* @param obj the object to extract the <code>short</code> value
* from
* @return the value of the field converted to type <code>short</code>
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not
* an instance of the class or interface declaring the
* underlying field (or a subclass or implementor
* thereof), or if the field value cannot be
* converted to the type <code>short</code> by a
* widening conversion.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#get
*/
public native short getShort(Object obj)
throws IllegalArgumentException, IllegalAccessException;
/**
* Gets the value of a static or instance field of type
* <code>int</code> or of another primitive type convertible to
* type <code>int</code> via a widening conversion.
*
* @param obj the object to extract the <code>int</code> value
* from
* @return the value of the field converted to type <code>int</code>
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not
* an instance of the class or interface declaring the
* underlying field (or a subclass or implementor
* thereof), or if the field value cannot be
* converted to the type <code>int</code> by a
* widening conversion.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#get
*/
public native int getInt(Object obj)
throws IllegalArgumentException, IllegalAccessException;
/**
* Gets the value of a static or instance field of type
* <code>long</code> or of another primitive type convertible to
* type <code>long</code> via a widening conversion.
*
* @param obj the object to extract the <code>long</code> value
* from
* @return the value of the field converted to type <code>long</code>
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not
* an instance of the class or interface declaring the
* underlying field (or a subclass or implementor
* thereof), or if the field value cannot be
* converted to the type <code>long</code> by a
* widening conversion.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#get
*/
public native long getLong(Object obj)
throws IllegalArgumentException, IllegalAccessException;
/**
* Gets the value of a static or instance field of type
* <code>float</code> or of another primitive type convertible to
* type <code>float</code> via a widening conversion.
*
* @param obj the object to extract the <code>float</code> value
* from
* @return the value of the field converted to type <code>float</code>
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not
* an instance of the class or interface declaring the
* underlying field (or a subclass or implementor
* thereof), or if the field value cannot be
* converted to the type <code>float</code> by a
* widening conversion.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#get
*/
public native float getFloat(Object obj)
throws IllegalArgumentException, IllegalAccessException;
/**
* Gets the value of a static or instance field of type
* <code>double</code> or of another primitive type convertible to
* type <code>double</code> via a widening conversion.
*
* @param obj the object to extract the <code>double</code> value
* from
* @return the value of the field converted to type <code>double</code>
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not
* an instance of the class or interface declaring the
* underlying field (or a subclass or implementor
* thereof), or if the field value cannot be
* converted to the type <code>double</code> by a
* widening conversion.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#get
*/
public native double getDouble(Object obj)
throws IllegalArgumentException, IllegalAccessException;
/**
* Sets the field represented by this <code>Field</code> object on the
* specified object argument to the specified new value. The new
* value is automatically unwrapped if the underlying field has a
* primitive type.
*
* <p>The operation proceeds as follows:
*
* <p>If the underlying field is static, the <code>obj</code> argument is
* ignored; it may be null.
*
* <p>Otherwise the underlying field is an instance field. If the
* specified object argument is null, the method throws a
* <code>NullPointerException</code>. If the specified object argument is not
* an instance of the class or interface declaring the underlying
* field, the method throws an <code>IllegalArgumentException</code>.
*
* <p>If this <code>Field</code> object enforces Java language access control, and
* the underlying field is inaccessible, the method throws an
* <code>IllegalAccessException</code>.
*
* <p>If the underlying field is final, the method throws an
* <code>IllegalAccessException</code>.
*
* <p>If the underlying field is of a primitive type, an unwrapping
* conversion is attempted to convert the new value to a value of
* a primitive type. If this attempt fails, the method throws an
* <code>IllegalArgumentException</code>.
*
* <p>If, after possible unwrapping, the new value cannot be
* converted to the type of the underlying field by an identity or
* widening conversion, the method throws an
* <code>IllegalArgumentException</code>.
*
* <p>If the underlying field is static, the class that declared the
* field is initialized if it has not already been initialized.
*
* <p>The field is set to the possibly unwrapped and widened new value.
*
* <p>If the field is hidden in the type of <code>obj</code>,
* the field's value is set according to the preceding rules.
*
* @param obj the object whose field should be modified
* @param value the new value for the field of <code>obj</code>
* being modified
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof),
* or if an unwrapping conversion fails.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
*/
public native void set(Object obj, Object value)
throws IllegalArgumentException, IllegalAccessException;
/**
* Sets the value of a field as a <code>boolean</code> on the specified object.
* This method is equivalent to
* <code>set(obj, zObj)</code>,
* where <code>zObj</code> is a <code>Boolean</code> object and
* <code>zObj.booleanValue() == z</code>.
*
* @param obj the object whose field should be modified
* @param z the new value for the field of <code>obj</code>
* being modified
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof),
* or if an unwrapping conversion fails.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#set
*/
public native void setBoolean(Object obj, boolean z)
throws IllegalArgumentException, IllegalAccessException;
/**
* Sets the value of a field as a <code>byte</code> on the specified object.
* This method is equivalent to
* <code>set(obj, bObj)</code>,
* where <code>bObj</code> is a <code>Byte</code> object and
* <code>bObj.byteValue() == b</code>.
*
* @param obj the object whose field should be modified
* @param b the new value for the field of <code>obj</code>
* being modified
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof),
* or if an unwrapping conversion fails.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#set
*/
public native void setByte(Object obj, byte b)
throws IllegalArgumentException, IllegalAccessException;
/**
* Sets the value of a field as a <code>char</code> on the specified object.
* This method is equivalent to
* <code>set(obj, cObj)</code>,
* where <code>cObj</code> is a <code>Character</code> object and
* <code>cObj.charValue() == c</code>.
*
* @param obj the object whose field should be modified
* @param c the new value for the field of <code>obj</code>
* being modified
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof),
* or if an unwrapping conversion fails.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#set
*/
public native void setChar(Object obj, char c)
throws IllegalArgumentException, IllegalAccessException;
/**
* Sets the value of a field as a <code>short</code> on the specified object.
* This method is equivalent to
* <code>set(obj, sObj)</code>,
* where <code>sObj</code> is a <code>Short</code> object and
* <code>sObj.shortValue() == s</code>.
*
* @param obj the object whose field should be modified
* @param s the new value for the field of <code>obj</code>
* being modified
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof),
* or if an unwrapping conversion fails.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#set
*/
public native void setShort(Object obj, short s)
throws IllegalArgumentException, IllegalAccessException;
/**
* Sets the value of a field as an <code>int</code> on the specified object.
* This method is equivalent to
* <code>set(obj, iObj)</code>,
* where <code>iObj</code> is a <code>Integer</code> object and
* <code>iObj.intValue() == i</code>.
*
* @param obj the object whose field should be modified
* @param i the new value for the field of <code>obj</code>
* being modified
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof),
* or if an unwrapping conversion fails.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#set
*/
public native void setInt(Object obj, int i)
throws IllegalArgumentException, IllegalAccessException;
/**
* Sets the value of a field as a <code>long</code> on the specified object.
* This method is equivalent to
* <code>set(obj, lObj)</code>,
* where <code>lObj</code> is a <code>Long</code> object and
* <code>lObj.longValue() == l</code>.
*
* @param obj the object whose field should be modified
* @param l the new value for the field of <code>obj</code>
* being modified
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof),
* or if an unwrapping conversion fails.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#set
*/
public native void setLong(Object obj, long l)
throws IllegalArgumentException, IllegalAccessException;
/**
* Sets the value of a field as a <code>float</code> on the specified object.
* This method is equivalent to
* <code>set(obj, fObj)</code>,
* where <code>fObj</code> is a <code>Float</code> object and
* <code>fObj.floatValue() == f</code>.
*
* @param obj the object whose field should be modified
* @param f the new value for the field of <code>obj</code>
* being modified
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof),
* or if an unwrapping conversion fails.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#set
*/
public native void setFloat(Object obj, float f)
throws IllegalArgumentException, IllegalAccessException;
/**
* Sets the value of a field as a <code>double</code> on the specified object.
* This method is equivalent to
* <code>set(obj, dObj)</code>,
* where <code>dObj</code> is a <code>Double</code> object and
* <code>dObj.doubleValue() == d</code>.
*
* @param obj the object whose field should be modified
* @param d the new value for the field of <code>obj</code>
* being modified
*
* @exception IllegalAccessException if the underlying field
* is inaccessible.
* @exception IllegalArgumentException if the specified object is not an
* instance of the class or interface declaring the underlying
* field (or a subclass or implementor thereof),
* or if an unwrapping conversion fails.
* @exception NullPointerException if the specified object is null
* and the field is an instance field.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
* @see Field#set
*/
public native void setDouble(Object obj, double d)
throws IllegalArgumentException, IllegalAccessException;
/*
* Utility routine to paper over array type names
*/
static String getTypeName(Class type) {
if (type.isArray()) {
try {
Class cl = type;
int dimensions = 0;
while (cl.isArray()) {
dimensions++;
cl = cl.getComponentType();
}
StringBuffer sb = new StringBuffer();
sb.append(cl.getName());
for (int i = 0; i < dimensions; i++) {
sb.append("[]");
}
return sb.toString();
} catch (Throwable e) { /*FALLTHRU*/ }
}
return type.getName();
}
}