JSP Out Object

In this JSP tutorial, you will learn about out object and its methods viz. clear, clearBuffer, flush, isAutoFlush, getBufferSize, getRemaining, newLine, print and println.

out object denotes the Output stream in the context of page. The class or the interface name of the object out is jsp.JspWriter.

The out object is written as:

The object that write to the JSP’s output stream is defined by the out object.

Methods of out Object:

There are numerous methods available for out Object, such as:

• clear
• clearBuffer
• flush
• isAutoFlush
• getBufferSize
• getRemaining
• newLine
• print
• println

Detailed below is the usage with syntax, example and explanation of above methods.

clear:

As the name implies, the clear method of out object is used to clear the output buffer. This method does not write any contents to the client. An exception is thrown by this method if the buffer was flushed.

General syntax of clear method of out object is as follows:

clearBuffer:

The clearBuffer method of out object is used to clear the output buffer. This method does not write any contents to the client.

The only difference between the clear method of out object and clearBuffer method is

• clear method throws an exception when the buffer is flushed.
• clearBuffer method does not throw an exception when the buffer is flushed.

General syntax of clearBuffer method of out object is as follows:

For example

out.clearBuffer();

For example

flush:

Two methods of out object, clear and clearBuffer are used to clear the output buffer without writing any contents to the client. If you wish to flush the buffer and write contents to the client, then you can use the flush method of out object. The flush method of out object is used to flush the buffer by writing the contents to the client.

General syntax of flush method of out object is as follows:

For example:

The above example will output only the first line of text. This text will be the only thing viewed in the browser. In the above example, no forwarding will take place. This is because of the out.flush() method. This method will flush the JspWriter buffer. Once the content is written to the browser, a forward cannot be invoked. Trying this throws the exception IllegalStateException. The user can handle this exception by catching it using the catch block. Handling Exceptions will be covered in detail in a later section of this tutorial.

isAutoFlush:

The isAutoFlush method of out object returns a true value if the output buffer is automatically flushed.

General syntax of isAutoFlush method of out object is as follows:

The returned value from this method is Boolean value of true or false.

getBufferSize:

The getBufferSize method of out object is used to return the size of the buffer. The returned value of the size of the buffer is in bytes. If the output is not buffered, then the getBufferSize method returns a 0 byte.

General syntax of getBufferSize method of out object is as follows:

The return value from the above method is in bytes.

For example:

getRemaining:

The getRemaining method of out object is used to return the number of empty bytes in the buffer.

General syntax of getRemaining method of out object is as follows:

newLine:

As the name implies, the newLine method of out object is used to write a newline character to the output.

The general syntax of newLine method of out object is as follows:

For example:

If a JSP program has the following statements in sequence

Then the output would be as follows:

The newLine method of out object gives a new line to the output and thus, the parameter given in third out.write statement "To Exforsys Training" is written in the next line.

print:

The print method of out object writes the value to the output without a newline character.

General syntax of print method of out object is as follows:

For example:

If a JSP program has the following statements in sequence

would give output as

This is because the print method of out object writes the output without a newline character.

println:

The println method of out object is used to write the value to the output, including the newline character.

General syntax of println method of out object is as follows:

For example:

Here if the value of ex is 5 then the output is

Here the string concatenation operator + is used along with println method of out object.