Java.io.ObjectInputStream Class in Java | Set 2
Java.io.ObjectInputStream Class in Java | Set 1
Note :
Java codes mentioned in this article won’t run on Online IDE as the file used in the code doesn’t exists online. So, to verify the working of the codes, you can copy them to your System and can run it over there.
More Methods of ObjectInputStream Class :
- defaultReadObject() : java.io.ObjectInputStream.defaultReadObject() reads the non-static field of the current class from the Input Stream. We use readObject() method of the serialized class to call this method.
Syntax :public void defaultReadObject() Parameters : ----------- Return : void Exception : -> IOException : in case of any IO error occurs. -> ClassNotFoundException : if the class of Object(being serialized) is not found -> NotActiveException : if the Stream is not reading.
- readObject() : java.io.ObjectInputStream.readObject() reads an object from the serialized class. This method is used to call the defaultReadObject. If the class is deserialized by defaut, then it can be overridden using the readObject and writeObject methods.
Syntax :public void defaultReadObject() Parameters : public final Object readObject() Return : void Exception : -> IOException : in case of any IO error occurs. -> ClassNotFoundException : if the class of Object(being serialized) is not found -> OptionalDataException : if instead of object, primitive data is found. -> InvalidClassException : is there is something wrong with serialized class
// Java program explaining the working of // readObject() and defaultReadObject() import java.io.*; public class NewClass { public static void main(String[] args) throws IOException, ClassNotFoundException { // create a new file with an ObjectOutputStream and ObjectInputStream FileOutputStream geek_out = new FileOutputStream("GEEKS.txt"); ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out); ObjectInputStream Geek_inStream = new ObjectInputStream(new FileInputStream("GEEKS.txt")); // These are ObjectOutputStream methods, Don't bother about these methods // As they are covered in other articles you can refer them geek_outStream.writeObject(new Geek()); geek_outStream.flush(); // Use of readObject() : Geek a = (Geek) Geek_inStream.readObject(); // Using both readObject and defaultReadObject(); System.out.println("Using defaultReadObject by readObject : "+ a.s); } static class Geek implements Serializable { String s = "GeeksForGeeks"; private void readObject(ObjectInputStream test)throws IOException, ClassNotFoundException { // Use of defaultReadObject() : test.defaultReadObject(); } } } |
output :
Using defaultReadObject by readObject : GeeksForGeeks
Syntax :
public int available() Parameters : ----------- Return : no. of bytes of that can be read without being blocked Exception : -> IOException : in case of any IO error occurs.
Syntax :
public void close() Parameters : ----------- Return : void Exception : -> IOException : in case of any IO error occurs.
Syntax :
public short readShort() Parameters : public final Object readObject() Return : reads 16 bit short. Exception : -> IOException : in case of any IO error occurs. -> EOFException : if End of stream is reached
// Java program explaining the working of // available(), readShort(),close() import java.io.*; public class NewClass { public static void main(String[] args) throws IOException, ClassNotFoundException { // create a new file with an ObjectOutputStream and ObjectInputStream FileOutputStream geek_out = new FileOutputStream("GEEKS.txt"); ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out); ObjectInputStream Geek_inStream = new ObjectInputStream(new FileInputStream("GEEKS.txt")); // These are ObjectOutputStream methods, Don't bother about these methods // As they are covered in other articles you can refer them geek_outStream.writeShort(3050); geek_outStream.writeUTF("gEEKSArehERE"); geek_outStream.flush(); // Use of available() method : System.out.println("Use of available() : " + Geek_inStream.available()); // Use of readShort() method : System.out.println("Use of readShort() : " + Geek_inStream.readShort()); // Use of close() method : to release the resources assigned to Geek_inStream System.out.println("Closing the stream"); Geek_inStream.close(); } } |
Output :
Use of available() : 16 Use of readShort() : 3050 Closing the stream
Syntax :
public String readUTF() Parameters : public final Object readObject() Return : reads String in modified UTF-8 (Unicode Transformation Format) format Exception : -> IOException : in case of any IO error occurs.
// Java program explaining the working of readUTF() import java.io.*; public class NewClass { public static void main(String[] args) throws IOException, ClassNotFoundException { // create a new file with an ObjectOutputStream and ObjectInputStream FileOutputStream geek_out = new FileOutputStream("GEEKS.txt"); ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out); ObjectInputStream Geek_inStream = new ObjectInputStream(new FileInputStream("GEEKS.txt")); // These are ObjectOutputStream methods, Don't bother about these methods // As they are covered in other articles you can refer them geek_outStream.writeUTF("gEEKSArehERE"); geek_outStream.flush(); // Use of readUTF() method : System.out.println("Use of readUTF() : " + Geek_inStream.readUTF()); } } |
Output :
Use of readUTF() : gEEKSArehERE
Syntax :
public int skipBytes(int maxlen) Parameters : maxlen : max. no. of bytes to be skipped Return : no. of bytes to be skipped Exception : -> IOException : in case of any IO error occurs.
// Java program explaining the working of skipBytes() import java.io.*; public class NewClass { public static void main(String[] args) throws IOException, ClassNotFoundException { // create a new file with an ObjectOutputStream and ObjectInputStream FileOutputStream geek_out = new FileOutputStream("GEEKS.txt"); ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out); ObjectInputStream Geek_inStream = new ObjectInputStream(new FileInputStream("GEEKS.txt")); // These are ObjectOutputStream methods, Don't bother about these methods // As they are covered in other articles you can refer them geek_outStream.writeUTF("gEEKSArehERE"); geek_outStream.flush(); // Use of skipBytes() : Geek_inStream.skipBytes(7); for (int i = 2; i < Geek_inStream.available(); i++) { System.out.print((char) Geek_inStream.readByte()); } } } |
Output :
Are
Syntax :
public void readFully(byte[] destination) Parameters : destination : the buffer in which the data is to be read Return : returns the 32 bit float read Exception : -> IOException : in case of any IO error occurs. -> EOFException : if End of stream is reached
// Java program explaining the working of readFully() import java.io.*; public class NewClass { public static void main(String[] args) throws IOException, ClassNotFoundException { // create a new file with an ObjectOutputStream and ObjectInputStream FileOutputStream geek_out = new FileOutputStream("GEEKS.txt"); ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out); ObjectInputStream Geek_inStream = new ObjectInputStream(new FileInputStream("GEEKS.txt")); // These are ObjectOutputStream methods, Don't bother about these methods // As they are covered in other articles you can refer them geek_outStream.writeUTF("gEEKSArehERE"); geek_outStream.flush(); // Use of readFully() : byte[] destination = new byte[14]; Geek_inStream.readFully(destination); String str = new String(destination); System.out.println("Use of readFully(destination, offset, maxlen) : "+str); } } |
Output :
Use of readFully(destination, offset, maxlen) : gEEKSArehERE
Syntax :
public void readFully(byte[] destination, int offset, int maxlen) Parameters : destination : the buffer in which the data is to be read offset : starting position of the buffer maxlen : max no. of bytes to be read Return : void Exception : -> IOException : in case of any IO error occurs. -> EOFException : if End of stream is reached
// Java program explaining the working of // readFully(byte[] destination, int offset, int maxlen) import java.io.*; public class NewClass { public static void main(String[] args) throws IOException, ClassNotFoundException { // create a new file with an ObjectOutputStream and ObjectInputStream FileOutputStream geek_out = new FileOutputStream("GEEKS.txt"); ObjectOutputStream geek_outStream = new ObjectOutputStream(geek_out); ObjectInputStream Geek_inStream = new ObjectInputStream(new FileInputStream("GEEKS.txt")); // These are ObjectOutputStream methods, Don't bother about these methods // As they are covered in other articles you can refer them geek_outStream.writeUTF("gEEKSArehERE"); geek_outStream.flush(); // Use of readFully(byte[] destination, int offset, int maxlen) : byte[] destination = new byte[14]; Geek_inStream.readFully(destination, 3, 7); String str = new String(destination); System.out.println("Use of readFully(destination, offset, maxlen) : "+ str); } } |
Output :
Use of readFully(destination, offset, maxlen) : geeks
Syntax :
public ObjectInputStream.GetField readFields() Parameters : ------- Return : GetField object reading the constant fields Exception : -> IOException : in case of any IO error occurs. -> ClassNotFoundException : if class of serialized object is not found
Syntax :
protected Class resolveClass(ObjectStreamClass desc) : means that the class object can be of any type, it is to be specified by the coder. Parameters : INS_class : instance of the specified Stream Class Return : Class Object equivalent to the Specified Stream Class Exception : -> IO Exception : if any IO exception occurs -> ClassNotFoundException : if the argumented class is not available.
Syntax :
public void registerValidation(ObjectInputValidation object, int order) Parameters : ------- Return : object : object to be validated order : Controls the order of callback. These are processed in no particular order Exception : -> NotActiveException : If IO stream is not ready to be read -> InvalidObjectException : if the argumented object to be validated is NULL.
enableResolveObject is called. It is called after an object has been read.
Syntax :
protected Object resolveObject(Object o) Parameters : o : object we want to substitue Return : --------- Exception : -> IOException : If IO error occurs.
enableResolveObject is called. It is called after an object has been read.
Syntax :
protected boolean enableResolveObject(boolean enable) Parameters : check : "true" to allow resolveObject() method Return : ----
Syntax :
protected ObjectStreamClass readClassDescriptor() Parameters : ------- Return : reads class descriptor
Syntax :
protected Object readObjectOverride() Parameters : ------- Return : reads object from the Stream
Syntax :
protected void readStreamHeader() Parameters : ------- Return : void
Syntax :
protected Class resolveProxyClass(String[] in_list) Parameters : in_List : interface names list, deserialized in the proxy class descriptor Return : Proxy class for specific Interface mentioned in the list
// Java Program explaining working of ObjectInputStream class methods import java.io.*; public class ObjectInputStreamDemo extends ObjectInputStream { public ObjectInputStreamDemo(InputStream in) throws IOException { super(in); } } public class NewClass { public static void main(String[] args) { String str = "Geeks"; try { // create a new file with an ObjectOutputStream and ObjectInputStream FileOutputStream geek_out = new FileOutputStream("test.txt"); ObjectOutputStream geek_in = new ObjectOutputStream(geek_out); ObjectInputStream geek_InStream = new ObjectInputStream(new FileInputStream("test.txt")); // These are ObjectOutputStream methods, Don't bother about these methods // As they are covered in other articles you can refer them geek_in.writeObject(new Test()); geek_in.writeUTF(str); geek_in.flush(); // Gvivg true to the resove Object to enable it geek_InStream.enableResolveObject(true); // Using resolveObject() : System.out.println("resoveObject() : " + geek_InStream.resolveObject(geek_InStream.readUTF())); // read the object and print the string Test a = (Test) geek_InStream.readObject(); // String value using readFields() methods : System.out.println("Using readFields() : " + a.geek); // Checking th use of registerValidation System.out.println("Testing the valiations : : : "); if (Test.geek.equals("Geeks For Geeks")) { System.out.println("\t\t\t\tWorking Perfect "); } else { System.out.println("Something wrong with the validations : "); } } catch (Exception excpt) { System.out.println("Error"); excpt.printStackTrace(); } } static class Test implements Serializable, ObjectInputValidation { static String geek = "Geeks For Geeks"; private String readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { // use of readFields() method : ObjectInputStream.GetField getfield = in.readFields(); // USe of registerValidation() method : in.registerValidation(this, 0); // Returning String "geek" to the main return (String) getfield.get("geek", null); } @Override public void validateObject() throws InvalidObjectException { throw new UnsupportedOperationException("Not supported yet."); } } } |
Output :
Using resoveObject() : Geeks Using readFields() : Geeks For Geeks Testing the valiations : : : Working Perfect
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