A {@code Field} permits widening conversions to occur during a get or * set access operation, but throws an {@code IllegalArgumentException} 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 Kenneth Russell * @author Nakul Saraiya */ public final class Field extends AccessibleObject implements Member { private int accessFlags; private Class declaringClass; private int dexFieldIndex; private int offset; private Class type; private Field() { } /** * Returns the {@code Class} object representing the class or interface * that declares the field represented by this {@code Field} object. */ public Class getDeclaringClass() { return declaringClass; } /** * Returns the name of the field represented by this {@code Field} object. */ public String getName() { if (dexFieldIndex == -1) { // Proxy classes have 1 synthesized static field with no valid dex index. if (!declaringClass.isProxy()) { throw new AssertionError(); } return "throws"; } Dex dex = declaringClass.getDex(); int nameIndex = dex.nameIndexFromFieldIndex(dexFieldIndex); return declaringClass.getDexCacheString(dex, nameIndex); } /** * Returns the Java language modifiers for the field represented * by this {@code Field} object, as an integer. The {@code Modifier} class should * be used to decode the modifiers. * * @see Modifier */ public int getModifiers() { return accessFlags & 0xffff; // mask out bits not used by Java } /** * Returns {@code true} if this field represents an element of * an enumerated type; returns {@code false} otherwise. * * @return {@code true} if and only if this field represents an element of * an enumerated type. * @since 1.5 */ public boolean isEnumConstant() { return (getModifiers() & Modifier.ENUM) != 0; } /** * Returns {@code true} if this field is a synthetic * field; returns {@code false} otherwise. * * @return true if and only if this field is a synthetic * field as defined by the Java Language Specification. * @since 1.5 */ public boolean isSynthetic() { return Modifier.isSynthetic(getModifiers()); } /** * Returns a {@code Class} object that identifies the * declared type for the field represented by this * {@code Field} object. * * @return a {@code Class} object identifying the declared * type of the field represented by this object */ public Class getType() { return type; } /** * Returns a {@code Type} object that represents the declared type for * the field represented by this {@code Field} object. * *
If the {@code Type} is a parameterized type, the * {@code Type} object returned must accurately reflect the * actual type parameters used in the source code. * *
If the type of the underlying field is a type variable or a * parameterized type, it is created. Otherwise, it is resolved. * * @return a {@code Type} object that represents the declared type for * the field represented by this {@code Field} object * @throws GenericSignatureFormatError if the generic field * signature does not conform to the format specified in * The Java™ Virtual Machine Specification * @throws TypeNotPresentException if the generic type * signature of the underlying field refers to a non-existent * type declaration * @throws MalformedParameterizedTypeException if the generic * signature of the underlying field refers to a parameterized type * that cannot be instantiated for any reason * @since 1.5 */ public Type getGenericType() { String signatureAttribute = getSignatureAttribute(); ClassLoader cl = declaringClass.getClassLoader(); GenericSignatureParser parser = new GenericSignatureParser(cl); parser.parseForField(declaringClass, signatureAttribute); Type genericType = parser.fieldType; if (genericType == null) { genericType = getType(); } return genericType; } private String getSignatureAttribute() { String[] annotation = getSignatureAnnotation(); if (annotation == null) { return null; } StringBuilder result = new StringBuilder(); for (String s : annotation) { result.append(s); } return result.toString(); } private native String[] getSignatureAnnotation(); /** * Compares this {@code Field} against the specified object. Returns * true if the objects are the same. Two {@code Field} 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() == other.getName()) && (getType() == other.getType()); } return false; } /** * Returns a hashcode for this {@code Field}. 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}. 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: *
* public static final int java.lang.Thread.MIN_PRIORITY
* private int java.io.FileDescriptor.fd
*
*
* The modifiers are placed in canonical order as specified by * "The Java Language Specification". This is {@code public}, * {@code protected} or {@code private} first, and then other * modifiers in the following order: {@code static}, {@code final}, * {@code transient}, {@code volatile}. */ public String toString() { int mod = getModifiers(); return (((mod == 0) ? "" : (Modifier.toString(mod) + " ")) + getTypeName(getType()) + " " + getTypeName(getDeclaringClass()) + "." + getName()); } /** * Returns a string describing this {@code Field}, including * its generic type. The format is the access modifiers for the * field, if any, followed by the generic 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. * *
The modifiers are placed in canonical order as specified by * "The Java Language Specification". This is {@code public}, * {@code protected} or {@code private} first, and then other * modifiers in the following order: {@code static}, {@code final}, * {@code transient}, {@code volatile}. * * @return a string describing this {@code Field}, including * its generic type * * @since 1.5 */ public String toGenericString() { int mod = getModifiers(); Type fieldType = getGenericType(); return (((mod == 0) ? "" : (Modifier.toString(mod) + " ")) + ((fieldType instanceof Class) ? getTypeName((Class)fieldType): fieldType.toString())+ " " + getTypeName(getDeclaringClass()) + "." + getName()); } /** * Returns the value of the field represented by this {@code Field}, on * the specified object. The value is automatically wrapped in an * object if it has a primitive type. * *
The underlying field's value is obtained as follows: * *
If the underlying field is a static field, the {@code obj} argument * is ignored; it may be null. * *
Otherwise, the underlying field is an instance field. If the * specified {@code obj} argument is null, the method throws a * {@code NullPointerException}. If the specified object is not an * instance of the class or interface declaring the underlying * field, the method throws an {@code IllegalArgumentException}. * *
If this {@code Field} object is enforcing Java language access control, and * the underlying field is inaccessible, the method throws an * {@code IllegalAccessException}. * If the underlying field is static, the class that declared the * field is initialized if it has not already been initialized. * *
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. * *
If the field is hidden in the type of {@code obj}, * the field's value is obtained according to the preceding rules. * * @param object object from which the represented field's value is * to be extracted * @return the value of the represented field in object * {@code obj}; primitive values are wrapped in an appropriate * object before being returned * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and 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 object) throws IllegalAccessException, IllegalArgumentException; /** * Gets the value of a static or instance {@code boolean} field. * * @param object the object to extract the {@code boolean} value * from * @return the value of the {@code boolean} field * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and 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} 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 object) throws IllegalAccessException, IllegalArgumentException; /** * Gets the value of a static or instance {@code byte} field. * * @param object the object to extract the {@code byte} value * from * @return the value of the {@code byte} field * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and 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} 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 object) throws IllegalAccessException, IllegalArgumentException; /** * Gets the value of a static or instance field of type * {@code char} or of another primitive type convertible to * type {@code char} via a widening conversion. * * @param object the object to extract the {@code char} value * from * @return the value of the field converted to type {@code char} * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and 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} 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 object) throws IllegalAccessException, IllegalArgumentException; /** * Gets the value of a static or instance field of type * {@code short} or of another primitive type convertible to * type {@code short} via a widening conversion. * * @param object the object to extract the {@code short} value * from * @return the value of the field converted to type {@code short} * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and 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} 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 object) throws IllegalAccessException, IllegalArgumentException; /** * Gets the value of a static or instance field of type * {@code int} or of another primitive type convertible to * type {@code int} via a widening conversion. * * @param object the object to extract the {@code int} value * from * @return the value of the field converted to type {@code int} * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and 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} 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 object) throws IllegalAccessException, IllegalArgumentException; /** * Gets the value of a static or instance field of type * {@code long} or of another primitive type convertible to * type {@code long} via a widening conversion. * * @param object the object to extract the {@code long} value * from * @return the value of the field converted to type {@code long} * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and 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} 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 object) throws IllegalAccessException, IllegalArgumentException; /** * Gets the value of a static or instance field of type * {@code float} or of another primitive type convertible to * type {@code float} via a widening conversion. * * @param object the object to extract the {@code float} value * from * @return the value of the field converted to type {@code float} * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and 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} 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 object) throws IllegalAccessException, IllegalArgumentException; /** * Gets the value of a static or instance field of type * {@code double} or of another primitive type convertible to * type {@code double} via a widening conversion. * * @param object the object to extract the {@code double} value * from * @return the value of the field converted to type {@code double} * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and 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} 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 object) throws IllegalAccessException, IllegalArgumentException; /** * Sets the field represented by this {@code Field} 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. * *
The operation proceeds as follows: * *
If the underlying field is static, the {@code obj} argument is * ignored; it may be null. * *
Otherwise the underlying field is an instance field. If the * specified object argument is null, the method throws a * {@code NullPointerException}. If the specified object argument is not * an instance of the class or interface declaring the underlying * field, the method throws an {@code IllegalArgumentException}. * *
If this {@code Field} object is enforcing Java language access control, and * the underlying field is inaccessible, the method throws an * {@code IllegalAccessException}. * *
If the underlying field is final, the method throws an * {@code IllegalAccessException} unless {@code setAccessible(true)} * has succeeded for this {@code Field} object * and the field is non-static. Setting a final field in this way * is meaningful only during deserialization or reconstruction of * instances of classes with blank final fields, before they are * made available for access by other parts of a program. Use in * any other context may have unpredictable effects, including cases * in which other parts of a program continue to use the original * value of this field. * *
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}. * *
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}. * *
If the underlying field is static, the class that declared the * field is initialized if it has not already been initialized. * *
The field is set to the possibly unwrapped and widened new value. * *
If the field is hidden in the type of {@code obj}, * the field's value is set according to the preceding rules. * * @param object the object whose field should be modified * @param value the new value for the field of {@code obj} * being modified * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and the underlying * field is either inaccessible or final. * @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 object, Object value) throws IllegalAccessException, IllegalArgumentException; /** * Sets the value of a field as a {@code boolean} on the specified object. * This method is equivalent to * {@code set(obj, zObj)}, * where {@code zObj} is a {@code Boolean} object and * {@code zObj.booleanValue() == z}. * * @param object the object whose field should be modified * @param value the new value for the field of {@code obj} * being modified * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and the underlying * field is either inaccessible or final. * @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 object, boolean value) throws IllegalAccessException, IllegalArgumentException; /** * Sets the value of a field as a {@code byte} on the specified object. * This method is equivalent to * {@code set(obj, bObj)}, * where {@code bObj} is a {@code Byte} object and * {@code bObj.byteValue() == b}. * * @param object the object whose field should be modified * @param value the new value for the field of {@code obj} * being modified * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and the underlying * field is either inaccessible or final. * @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 object, byte value) throws IllegalAccessException, IllegalArgumentException; /** * Sets the value of a field as a {@code char} on the specified object. * This method is equivalent to * {@code set(obj, cObj)}, * where {@code cObj} is a {@code Character} object and * {@code cObj.charValue() == c}. * * @param object the object whose field should be modified * @param value the new value for the field of {@code obj} * being modified * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and the underlying * field is either inaccessible or final. * @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 object, char value) throws IllegalAccessException, IllegalArgumentException; /** * Sets the value of a field as a {@code short} on the specified object. * This method is equivalent to * {@code set(obj, sObj)}, * where {@code sObj} is a {@code Short} object and * {@code sObj.shortValue() == s}. * * @param object the object whose field should be modified * @param value the new value for the field of {@code obj} * being modified * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and the underlying * field is either inaccessible or final. * @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 object, short value) throws IllegalAccessException, IllegalArgumentException; /** * Sets the value of a field as an {@code int} on the specified object. * This method is equivalent to * {@code set(obj, iObj)}, * where {@code iObj} is a {@code Integer} object and * {@code iObj.intValue() == i}. * * @param object the object whose field should be modified * @param value the new value for the field of {@code obj} * being modified * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and the underlying * field is either inaccessible or final. * @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 object, int value) throws IllegalAccessException, IllegalArgumentException; /** * Sets the value of a field as a {@code long} on the specified object. * This method is equivalent to * {@code set(obj, lObj)}, * where {@code lObj} is a {@code Long} object and * {@code lObj.longValue() == l}. * * @param object the object whose field should be modified * @param value the new value for the field of {@code obj} * being modified * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and the underlying * field is either inaccessible or final. * @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 object, long value) throws IllegalAccessException, IllegalArgumentException; /** * Sets the value of a field as a {@code float} on the specified object. * This method is equivalent to * {@code set(obj, fObj)}, * where {@code fObj} is a {@code Float} object and * {@code fObj.floatValue() == f}. * * @param object the object whose field should be modified * @param value the new value for the field of {@code obj} * being modified * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and the underlying * field is either inaccessible or final. * @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 object, float value) throws IllegalAccessException, IllegalArgumentException; /** * Sets the value of a field as a {@code double} on the specified object. * This method is equivalent to * {@code set(obj, dObj)}, * where {@code dObj} is a {@code Double} object and * {@code dObj.doubleValue() == d}. * * @param object the object whose field should be modified * @param value the new value for the field of {@code obj} * being modified * * @exception IllegalAccessException if this {@code Field} object * is enforcing Java language access control and the underlying * field is either inaccessible or final. * @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 object, double value) throws IllegalAccessException, IllegalArgumentException; /* * 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(); } /** * @throws NullPointerException {@inheritDoc} * @since 1.5 */ @Override public A getAnnotation(Class annotationType) { if (annotationType == null) { throw new NullPointerException("annotationType == null"); } return getAnnotationNative(annotationType); } private native A getAnnotationNative(Class annotationType); @Override public boolean isAnnotationPresent(Class annotationType) { if (annotationType == null) { throw new NullPointerException("annotationType == null"); } return isAnnotationPresentNative(annotationType); } private native boolean isAnnotationPresentNative(Class annotationType); /** * @since 1.5 */ @Override public native Annotation[] getDeclaredAnnotations(); /** * Returns the index of this field's ID in its dex file. * * @hide */ public int getDexFieldIndex() { return dexFieldIndex; } /** * Returns the offset of the field within an instance, or for static fields, the class. * * @hide */ public int getOffset() { return offset; } }