org.apache.harmony.security.asn1

Class ASN1Choice

java.lang.Object

org.apache.harmony.security.asn1.ASN1Type

org.apache.harmony.security.asn1.ASN1Choice

All Implemented Interfaces:

ASN1Constants

public abstract class ASN1Choice
extends ASN1Type

This abstract class represents ASN.1 Choice type. To implement custom ASN.1 choice type an application class must provide implementation for the following methods: getIndex() getObjectToEncode() There are two ways to implement custom ASN.1 choice type: with application class that represents ASN.1 custom choice type or without. The key point is how a value of choice type is stored by application classes. For example, let's consider the following ASN.1 notations (see http://www.ietf.org/rfc/rfc3280.txt) Time ::= CHOICE { utcTime UTCTime, generalTime GeneralizedTime } Validity ::= SEQUENCE { notBefore Time, notAfter Time } 1)First approach: No application class to represent ASN.1 Time notation The Time notation is a choice of different time formats: UTC and Generalized. Both of them are mapped to java.util.Date object, so an application class that represents ASN.1 Validity notation may keep values as Date objects. So a custom ASN.1 Time choice type should map its notation to Date object. class Time { // custom ASN.1 choice class: maps Time to is notation public static final ASN1Choice asn1 = new ASN1Choice(new ASN1Type[] { ASN1GeneralizedTime.asn1, ASN1UTCTime.asn1 }) { public int getIndex(java.lang.Object object) { return 0; // always encode as ASN1GeneralizedTime } public Object getObjectToEncode(Object object) { // A value to be encoded value is a Date object // pass it to custom time class return object; } }; } class Validity { private Date notBefore; // choice as Date private Date notAfter; // choice as Date ... // constructors and other methods go here // custom ASN.1 sequence class: maps Validity class to is notation public static final ASN1Sequence ASN1 = new ASN1Sequence(new ASN1Type[] {Time.asn1, Time.asn1 }) { protected Object getObject(Object[] values) { // ASN.1 Time choice passed Data object - use it return new Validity((Date) values[0], (Date) values[1]); } protected void getValues(Object object, Object[] values) { Validity validity = (Validity) object; // pass Date objects to ASN.1 Time choice values[0] = validity.notBefore; values[1] = validity.notAfter; } } } 2)Second approach: There is an application class to represent ASN.1 Time notation If it is a matter what time format should be used to decode/encode Date objects a class to represent ASN.1 Time notation must be created. For example, class Time { private Date utcTime; private Date gTime; ... // constructors and other methods go here // custom ASN.1 choice class: maps Time to is notation public static final ASN1Choice asn1 = new ASN1Choice(new ASN1Type[] { ASN1GeneralizedTime.asn1, ASN1UTCTime.asn1 }) { public Object getDecodedObject(BerInputStream in) { // create Time object to pass as decoded value Time time = new Time(); if (in.choiceIndex==0) { // we decoded GeneralizedTime // store decoded Date value in corresponding field time.gTime = in.content; // return it return time; } else { // we decoded UTCTime // store decoded Date value in corresponding field time.utcTime = in.content; // return it return time; } } public int getIndex(java.lang.Object object) { Time time = (Time)object; if(time.utcTime!=null){ // encode Date as UTCTime return 1; } else { // otherwise encode Date as GeneralizedTime return 0; } } public Object getObjectToEncode(Object object) { Time time = (Time)object; if(time.utcTime!=null){ // encode Date as UTCTime return 1; } else { // otherwise encode Date as GeneralizedTime return 0; } } }; } So now Validity class must keep all values in Time object and its custom ASN.1 sequence class must handle this class of objects class Validity { private Time notBefore; // now it is a Time!!! private Time notAfter; // now it is a Time!!! ... // constructors and other methods go here // custom ASN.1 sequence class: maps Validity class to is notation public static final ASN1Sequence ASN1 = new ASN1Sequence(new ASN1Type[] {Time.asn1, Time.asn1 }) { protected Object getObject(Object[] values) { // We've gotten Time objects here !!! return new Validity((Time) values[0], (Time) values[1]); } protected void getValues(Object object, Object[] values) { Validity validity = (Validity) object; // pass Time objects to ASN.1 Time choice values[0] = validity.notBefore; values[1] = validity.notAfter; } } }

See Also:

ASN.1

Field Summary

Fields

Modifier and Type	Field and Description
ASN1Type[]	type

Fields inherited from class org.apache.harmony.security.asn1.ASN1Type

constrId, id

Fields inherited from interface org.apache.harmony.security.asn1.ASN1Constants

CLASS_APPLICATION, CLASS_CONTEXTSPECIFIC, CLASS_PRIVATE, CLASS_UNIVERSAL, PC_CONSTRUCTED, PC_PRIMITIVE, TAG_ANY, TAG_BITSTRING, TAG_BMPSTRING, TAG_BOOLEAN, TAG_C_BITSTRING, TAG_C_GENERALIZEDTIME, TAG_C_OCTETSTRING, TAG_C_SEQUENCE, TAG_C_SEQUENCEOF, TAG_C_SET, TAG_C_SETOF, TAG_C_UTCTIME, TAG_C_UTF8STRING, TAG_CHOICE, TAG_EMBEDDEDPDV, TAG_ENUM, TAG_EXTERNAL, TAG_GENERALIZEDTIME, TAG_GENERALSTRING, TAG_GRAPHICSTRING, TAG_IA5STRING, TAG_INSTANCEOF, TAG_INTEGER, TAG_ISO646STRING, TAG_NULL, TAG_NUMERICSTRING, TAG_OBJDESCRIPTOR, TAG_OCTETSTRING, TAG_OID, TAG_PRINTABLESTRING, TAG_REAL, TAG_RELATIVEOID, TAG_SEQUENCE, TAG_SEQUENCEOF, TAG_SET, TAG_SETOF, TAG_T61STRING, TAG_TELETEXSTRING, TAG_UNIVERSALSTRING, TAG_UTCTIME, TAG_UTF8STRING, TAG_VIDEOTEXSTRING, TAG_VISIBLESTRING

Constructor Summary

Constructors

Constructor and Description
ASN1Choice(ASN1Type[] type) Constructs ASN.1 choice type.

Method Summary

Modifier and Type	Method and Description
boolean	checkTag(int identifier) Tests whether one of choice alternatives has the same identifier or not.
Object	decode(BerInputStream in) Decodes ASN.1 type.
void	encodeASN(BerOutputStream out) Encodes ASN.1 type.
void	encodeContent(BerOutputStream out)
abstract int	getIndex(Object object)
abstract Object	getObjectToEncode(Object object)
void	setEncodingContent(BerOutputStream out)

Methods inherited from class org.apache.harmony.security.asn1.ASN1Type

decode, decode, decode, encode, getDecodedObject, getEncodedLength, toString, verify, verify

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

type

public final ASN1Type[] type

Constructor Detail

ASN1Choice

public ASN1Choice(ASN1Type[] type)

Constructs ASN.1 choice type.

Parameters:

type - - an array of one or more ASN.1 type alternatives.

Throws:

IllegalArgumentException - - type parameter is invalid

Method Detail

checkTag

public final boolean checkTag(int identifier)

Tests whether one of choice alternatives has the same identifier or not.

Specified by:

checkTag in class ASN1Type

Parameters:

identifier - - ASN.1 identifier to be verified

Returns:

- true if one of choice alternatives has the same identifier, otherwise false;

decode

public Object decode(BerInputStream in)
              throws IOException

Description copied from class: ASN1Type

Decodes ASN.1 type.

Specified by:

decode in class ASN1Type

Throws:

IOException - if an I/O error occurs or the end of the stream is reached

encodeASN

public void encodeASN(BerOutputStream out)

Description copied from class: ASN1Type

Encodes ASN.1 type.

Specified by:

encodeASN in class ASN1Type

encodeContent

public final void encodeContent(BerOutputStream out)

Specified by:

encodeContent in class ASN1Type

getIndex

public abstract int getIndex(Object object)

getObjectToEncode

public abstract Object getObjectToEncode(Object object)

setEncodingContent

public final void setEncodingContent(BerOutputStream out)

Specified by:

setEncodingContent in class ASN1Type