javax.servlet.jsp

Class JspWriter

java.lang.Object

java.io.Writer

javax.servlet.jsp.JspWriter

Known Direct Subclasses:: BodyContent

public abstract class JspWriter

extends java.io.Writer

The actions and template data in a JSP page is written using the JspWriter object that is referenced by the implicit variable out which is initialized automatically using methods in the PageContext object.

This abstract class emulates some of the functionality found in the java.io.BufferedWriter and java.io.PrintWriter classes, however it differs in that it throws java.io.IOException from the print methods while PrintWriter does not.

Buffering

The initial JspWriter object is associated with the PrintWriter object of the ServletResponse in a way that depends on whether the page is or is not buffered. If the page is not buffered, output written to this JspWriter object will be written through to the PrintWriter directly, which will be created if necessary by invoking the getWriter() method on the response object. But if the page is buffered, the PrintWriter object will not be created until the buffer is flushed and operations like setContentType() are legal. Since this flexibility simplifies programming substantially, buffering is the default for JSP pages.

Buffering raises the issue of what to do when the buffer is exceeded. Two approaches can be taken:

Exceeding the buffer is not a fatal error; when the buffer is exceeded, just flush the output.
Exceeding the buffer is a fatal error; when the buffer is exceeded, raise an exception.

Both approaches are valid, and thus both are supported in the JSP technology. The behavior of a page is controlled by the autoFlush attribute, which defaults to true. In general, JSP pages that need to be sure that correct and complete data has been sent to their client may want to set autoFlush to false, with a typical case being that where the client is an application itself. On the other hand, JSP pages that send data that is meaningful even when partially constructed may want to set autoFlush to true; such as when the data is sent for immediate display through a browser. Each application will need to consider their specific needs.

An alternative considered was to make the buffer size unbounded; but, this had the disadvantage that runaway computations would consume an unbounded amount of resources.

The "out" implicit variable of a JSP implementation class is of this type. If the page directive selects autoflush="true" then all the I/O operations on this class shall automatically flush the contents of the buffer if an overflow condition would result if the current operation were performed without a flush. If autoflush="false" then all the I/O operations on this class shall throw an IOException if performing the current operation would result in a buffer overflow condition.

See Also:: java.io.Writer, java.io.BufferedWriter, java.io.PrintWriter

Field Summary
`static int`	`DEFAULT_BUFFER` constant indicating that the Writer is buffered and is using the implementation default buffer size
`static int`	`NO_BUFFER` constant indicating that the Writer is not buffering output
`static int`	`UNBOUNDED_BUFFER` constant indicating that the Writer is buffered and is unbounded; this is used in BodyContent
`protected boolean`	`autoFlush`
`protected int`	`bufferSize`

Constructor Summary
`JspWriter(int bufferSize, boolean autoFlush)` protected constructor.

Method Summary
`void`	`clear()` Clear the contents of the buffer.
`void`	`clearBuffer()` Clears the current contents of the buffer.
`void`	`close()` Close the stream, flushing it first This method needs not be invoked explicitly for the initial JspWriter as the code generated by the JSP container will automatically include a call to close().
`void`	`flush()` Flush the stream.
`int`	`getBufferSize()` This method returns the size of the buffer used by the JspWriter.
`int`	`getRemaining()` This method returns the number of unused bytes in the buffer.
`boolean`	`isAutoFlush()` This method indicates whether the JspWriter is autoFlushing.
`void`	`newLine()` Write a line separator.
`void`	`print(boolean b)` Print a boolean value.
`void`	`print(char c)` Print a character.
`void`	`print(double d)` Print a double-precision floating-point number.
`void`	`print(float f)` Print a floating-point number.
`void`	`print(int i)` Print an integer.
`void`	`print(java.lang.Object obj)` Print an object.
`void`	`print(java.lang.String s)` Print a string.
`void`	`print(long l)` Print a long integer.
`void`	`print(s[] )` Print an array of characters.
`void`	`println()` Terminate the current line by writing the line separator string.
`void`	`println(boolean x)` Print a boolean value and then terminate the line.
`void`	`println(char x)` Print a character and then terminate the line.
`void`	`println(double x)` Print a double-precision floating-point number and then terminate the line.
`void`	`println(float x)` Print a floating-point number and then terminate the line.
`void`	`println(int x)` Print an integer and then terminate the line.
`void`	`println(java.lang.Object x)` Print an Object and then terminate the line.
`void`	`println(java.lang.String x)` Print a String and then terminate the line.
`void`	`println(long x)` Print a long integer and then terminate the line.
`void`	`println(x[] )` Print an array of characters and then terminate the line.

DEFAULT_BUFFER

public static final int DEFAULT_BUFFER

constant indicating that the Writer is buffered and is using the implementation default buffer size
Field Value:
-1

NO_BUFFER

public static final int NO_BUFFER

constant indicating that the Writer is not buffering output
Field Value:
0

UNBOUNDED_BUFFER

public static final int UNBOUNDED_BUFFER

constant indicating that the Writer is buffered and is unbounded; this is used in BodyContent
Field Value:
-2

autoFlush

protected boolean autoFlush

bufferSize

protected int bufferSize

JspWriter

protected JspWriter(int bufferSize,
                    boolean autoFlush)

protected constructor.

clear

public void clear()

Clear the contents of the buffer. If the buffer has been already been flushed then the clear operation shall throw an IOException to signal the fact that some data has already been irrevocably written to the client response stream.

clearBuffer

public void clearBuffer()

Clears the current contents of the buffer. Unlike clear(), this method will not throw an IOException if the buffer has already been flushed. It merely clears the current content of the buffer and returns.

close

public void close()

Close the stream, flushing it first
This method needs not be invoked explicitly for the initial JspWriter as the code generated by the JSP container will automatically include a call to close().
Closing a previously-closed stream, unlike flush(), has no effect.

flush

public void flush()

Flush the stream. If the stream has saved any characters from the various write() methods in a buffer, write them immediately to their intended destination. Then, if that destination is another character or byte stream, flush it. Thus one flush() invocation will flush all the buffers in a chain of Writers and OutputStreams.
The method may be invoked indirectly if the buffer size is exceeded.
Once a stream has been closed, further write() or flush() invocations will cause an IOException to be thrown.

getBufferSize

public int getBufferSize()

This method returns the size of the buffer used by the JspWriter.
Returns:
the size of the buffer in bytes, or 0 is unbuffered.

getRemaining

public int getRemaining()

This method returns the number of unused bytes in the buffer.
Returns:
the number of bytes unused in the buffer

isAutoFlush

public boolean isAutoFlush()

This method indicates whether the JspWriter is autoFlushing.
Returns:
if this JspWriter is auto flushing or throwing IOExceptions on buffer overflow conditions

newLine

public void newLine()

Write a line separator. The line separator string is defined by the system property line.separator, and is not necessarily a single newline ('\n') character.

print

public void print(boolean b)

Print a boolean value. The string produced by java.lang.String.valueOf(boolean) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
b - The boolean to be printed

print

public void print(char c)

Print a character. The character is translated into one or more bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
c - The char to be printed

print

public void print(double d)

Print a double-precision floating-point number. The string produced by java.lang.String.valueOf(double) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
d - The double to be printed
See Also:
java.lang.Double.toString(double)

print

public void print(float f)

Print a floating-point number. The string produced by java.lang.String.valueOf(float) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
f - The float to be printed
See Also:
java.lang.Float.toString(float)

print

public void print(int i)

Print an integer. The string produced by java.lang.String.valueOf(int) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
i - The int to be printed
See Also:
java.lang.Integer.toString(int)

print

public void print(java.lang.Object obj)

Print an object. The string produced by the java.lang.String.valueOf(Object) method is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
obj - The Object to be printed
See Also:
java.lang.Object.toString()

print

public void print(java.lang.String s)

Print a string. If the argument is null then the string "null" is printed. Otherwise, the string's characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
s - The String to be printed

print

public void print(long l)

Print a long integer. The string produced by java.lang.String.valueOf(long) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
Parameters:
l - The long to be printed
See Also:
java.lang.Long.toString(long)

print

public void print(s[] )

Print an array of characters. The characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
Parameters:

println

public void println()

Terminate the current line by writing the line separator string. The line separator string is defined by the system property line.separator, and is not necessarily a single newline character ('\n').

println

public void println(boolean x)

Print a boolean value and then terminate the line. This method behaves as though it invokes print(boolean) and then println().

println

public void println(char x)

Print a character and then terminate the line. This method behaves as though it invokes print(char) and then println().

println

public void println(double x)

Print a double-precision floating-point number and then terminate the line. This method behaves as though it invokes print(double) and then println().

println

public void println(float x)

Print a floating-point number and then terminate the line. This method behaves as though it invokes print(float) and then println().

println

public void println(int x)

Print an integer and then terminate the line. This method behaves as though it invokes print(int) and then println().

println

public void println(java.lang.Object x)

Print an Object and then terminate the line. This method behaves as though it invokes print(Object) and then println().

println

public void println(java.lang.String x)

Print a String and then terminate the line. This method behaves as though it invokes print(String) and then println().

println

public void println(long x)

Print a long integer and then terminate the line. This method behaves as though it invokes print(long) and then println().

println

public void println(x[] )

Print an array of characters and then terminate the line. This method behaves as though it invokes print(char[]) and then println().

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javax.servlet.jsp

Class JspWriter

Field Summary

Constructor Summary

Method Summary

Field Details

DEFAULT_BUFFER

NO_BUFFER

UNBOUNDED_BUFFER

autoFlush

bufferSize

Constructor Details

JspWriter

Method Details

clear

clearBuffer

close

flush

getBufferSize

getRemaining

isAutoFlush

newLine

print

print

print

print

print

print

print

print

print

println

println

println

println

println

println

println

println

println

println