JspWriter (Java EE 5 SDK) - Java Platform, Enterprise Edition v5.0 API Specifications

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javax.servlet.jsp
Class JspWriter

java.lang.Object
  java.io.Writer
      javax.servlet.jsp.JspWriter

All Implemented Interfaces:: Closeable, Flushable, Appendable

Direct Known Subclasses:: BodyContent

public abstract class JspWriter
extends Writer
extends 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:: Writer, BufferedWriter, PrintWriter

Field Summary

protected boolean autoFlush
          Whether the JspWriter is autoflushing.

protected int bufferSize
          The size of the buffer used by the JspWriter.

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.

Fields inherited from class java.io.Writer

lock

Constructor Summary

protected JspWriter(int bufferSize, boolean autoFlush)
          Protected constructor.

Method Summary

abstract void clear()
          Clear the contents of the buffer.

abstract void clearBuffer()
          Clears the current contents of the buffer.

abstract void close()
          Close the stream, flushing it first.

abstract void flush()
          Flush the stream.

int getBufferSize()
          This method returns the size of the buffer used by the JspWriter.

abstract int getRemaining()
          This method returns the number of unused bytes in the buffer.

boolean isAutoFlush()
          This method indicates whether the JspWriter is autoFlushing.

abstract void newLine()
          Write a line separator.

abstract void print(boolean b)
          Print a boolean value.

abstract void print(char c)
          Print a character.

abstract void print(char[] s)
          Print an array of characters.

abstract void print(double d)
          Print a double-precision floating-point number.

abstract void print(float f)
          Print a floating-point number.

abstract void print(int i)
          Print an integer.

abstract void print(long l)
          Print a long integer.

abstract void print(Object obj)
          Print an object.

abstract void print(String s)
          Print a string.

abstract void println()
          Terminate the current line by writing the line separator string.

abstract void println(boolean x)
          Print a boolean value and then terminate the line.

abstract void println(char x)
          Print a character and then terminate the line.

abstract void println(char[] x)
          Print an array of characters and then terminate the line.

abstract void println(double x)
          Print a double-precision floating-point number and then terminate the line.

abstract void println(float x)
          Print a floating-point number and then terminate the line.

abstract void println(int x)
          Print an integer and then terminate the line.

abstract void println(long x)
          Print a long integer and then terminate the line.

abstract void println(Object x)
          Print an Object and then terminate the line.

abstract void println(String x)
          Print a String and then terminate the line.

Methods inherited from class java.io.Writer

append, append, append, write, write, write, write, write

Methods inherited from class java.lang.Object

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

Field Summary
`protected boolean`	`autoFlush` Whether the JspWriter is autoflushing.
`protected int`	`bufferSize` The size of the buffer used by the JspWriter.
`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.

Fields inherited from class java.io.Writer
`lock`

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

Method Summary
`abstract void`	`clear()` Clear the contents of the buffer.
`abstract void`	`clearBuffer()` Clears the current contents of the buffer.
`abstract void`	`close()` Close the stream, flushing it first.
`abstract void`	`flush()` Flush the stream.
`int`	`getBufferSize()` This method returns the size of the buffer used by the JspWriter.
`abstract int`	`getRemaining()` This method returns the number of unused bytes in the buffer.
`boolean`	`isAutoFlush()` This method indicates whether the JspWriter is autoFlushing.
`abstract void`	`newLine()` Write a line separator.
`abstract void`	`print(boolean b)` Print a boolean value.
`abstract void`	`print(char c)` Print a character.
`abstract void`	`print(char[] s)` Print an array of characters.
`abstract void`	`print(double d)` Print a double-precision floating-point number.
`abstract void`	`print(float f)` Print a floating-point number.
`abstract void`	`print(int i)` Print an integer.
`abstract void`	`print(long l)` Print a long integer.
`abstract void`	`print(Object obj)` Print an object.
`abstract void`	`print(String s)` Print a string.
`abstract void`	`println()` Terminate the current line by writing the line separator string.
`abstract void`	`println(boolean x)` Print a boolean value and then terminate the line.
`abstract void`	`println(char x)` Print a character and then terminate the line.
`abstract void`	`println(char[] x)` Print an array of characters and then terminate the line.
`abstract void`	`println(double x)` Print a double-precision floating-point number and then terminate the line.
`abstract void`	`println(float x)` Print a floating-point number and then terminate the line.
`abstract void`	`println(int x)` Print an integer and then terminate the line.
`abstract void`	`println(long x)` Print a long integer and then terminate the line.
`abstract void`	`println(Object x)` Print an Object and then terminate the line.
`abstract void`	`println(String x)` Print a String and then terminate the line.

Methods inherited from class java.io.Writer
`append, append, append, write, write, write, write, write`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

NO_BUFFER

public static final int NO_BUFFER

Constant indicating that the Writer is not buffering output.

See Also:: Constant Field Values

DEFAULT_BUFFER

public static final int DEFAULT_BUFFER

Constant indicating that the Writer is buffered and is using the implementation default buffer size.

See Also:: Constant Field Values

UNBOUNDED_BUFFER

public static final int UNBOUNDED_BUFFER

Constant indicating that the Writer is buffered and is unbounded; this is used in BodyContent.

See Also:: Constant Field Values

bufferSize

protected int bufferSize

The size of the buffer used by the JspWriter.

autoFlush

protected boolean autoFlush

Whether the JspWriter is autoflushing.

Constructor Detail

JspWriter

protected JspWriter(int bufferSize,
                    boolean autoFlush)

Protected constructor.

Parameters:: bufferSize - the size of the buffer to be used by the JspWriter; autoFlush - whether the JspWriter should be autoflushing

Method Detail

newLine

public abstract void newLine()
                      throws IOException

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.

Throws:: IOException - If an I/O error occurs

print

public abstract void print(boolean b)
                    throws IOException

Print a boolean value. The string produced by String.valueOf(boolean) is written to the JspWriter's buffer or, if no buffer is used, directly to the underlying writer.

Parameters:: b - The boolean to be printed
Throws:: IOException - If an error occured while writing

print

public abstract void print(char c)
                    throws IOException

Print a character. The character is written to the JspWriter's buffer or, if no buffer is used, directly to the underlying writer.

Parameters:: c - The char to be printed
Throws:: IOException - If an error occured while writing

print

public abstract void print(int i)
                    throws IOException

Print an integer. The string produced by String.valueOf(int) is written to the JspWriter's buffer or, if no buffer is used, directly to the underlying writer.

Parameters:: i - The int to be printed
Throws:: IOException - If an error occured while writing
See Also:: Integer.toString(int)

print

public abstract void print(long l)
                    throws IOException

Print a long integer. The string produced by String.valueOf(long) is written to the JspWriter's buffer or, if no buffer is used, directly to the underlying writer.

Parameters:: l - The long to be printed
Throws:: IOException - If an error occured while writing
See Also:: Long.toString(long)

print

public abstract void print(float f)
                    throws IOException

Print a floating-point number. The string produced by String.valueOf(float) is written to the JspWriter's buffer or, if no buffer is used, directly to the underlying writer.

Parameters:: f - The float to be printed
Throws:: IOException - If an error occured while writing
See Also:: Float.toString(float)

print

public abstract void print(double d)
                    throws IOException

Print a double-precision floating-point number. The string produced by String.valueOf(double) is written to the JspWriter's buffer or, if no buffer is used, directly to the underlying writer.

Parameters:: d - The double to be printed
Throws:: IOException - If an error occured while writing
See Also:: Double.toString(double)

print

public abstract void print(char[] s)
                    throws IOException

Print an array of characters. The characters are written to the JspWriter's buffer or, if no buffer is used, directly to the underlying writer.

Parameters:: s - The array of chars to be printed
Throws:: NullPointerException - If s is null; IOException - If an error occured while writing

print

public abstract void print(String s)
                    throws IOException

Print a string. If the argument is null then the string "null" is printed. Otherwise, the string's characters are written to the JspWriter's buffer or, if no buffer is used, directly to the underlying writer.

Parameters:: s - The String to be printed
Throws:: IOException - If an error occured while writing

print

public abstract void print(Object obj)
                    throws IOException

Print an object. The string produced by the String.valueOf(Object) method is written to the JspWriter's buffer or, if no buffer is used, directly to the underlying writer.

Parameters:: obj - The Object to be printed
Throws:: IOException - If an error occured while writing
See Also:: Object.toString()

println

public abstract void println()
                      throws IOException

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').

Throws:: IOException - If an error occured while writing

println

public abstract void println(boolean x)
                      throws IOException

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

Parameters:: x - the boolean to write
Throws:: IOException - If an error occured while writing

println

public abstract void println(char x)
                      throws IOException

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

Parameters:: x - the char to write
Throws:: IOException - If an error occured while writing

println

public abstract void println(int x)
                      throws IOException

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

Parameters:: x - the int to write
Throws:: IOException - If an error occured while writing

println

public abstract void println(long x)
                      throws IOException

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

Parameters:: x - the long to write
Throws:: IOException - If an error occured while writing

println

public abstract void println(float x)
                      throws IOException

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

Parameters:: x - the float to write
Throws:: IOException - If an error occured while writing

println

public abstract void println(double x)
                      throws IOException

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

Parameters:: x - the double to write
Throws:: IOException - If an error occured while writing

println

public abstract void println(char[] x)
                      throws IOException

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

Parameters:: x - the char[] to write
Throws:: IOException - If an error occured while writing

println

public abstract void println(String x)
                      throws IOException

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

Parameters:: x - the String to write
Throws:: IOException - If an error occured while writing

println

public abstract void println(Object x)
                      throws IOException

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

Parameters:: x - the Object to write
Throws:: IOException - If an error occured while writing

clear

public abstract void clear()
                    throws IOException

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.

Throws:: IOException - If an I/O error occurs

clearBuffer

public abstract void clearBuffer()
                          throws IOException

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.

Throws:: IOException - If an I/O error occurs

flush

public abstract void flush()
                    throws IOException

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.

Specified by:: flush in interface Flushable
Specified by:: flush in class Writer

Throws:: IOException - If an I/O error occurs

close

public abstract void close()
                    throws IOException

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.

Specified by:: close in interface Closeable
Specified by:: close in class Writer

Throws:: IOException - If an I/O error occurs

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 abstract 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

Overview

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Tree

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Java EE 5 SDK

PREV CLASS NEXT CLASS

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Submit a bug or feature

JspWriter (Java EE 5 SDK) - Java Platform, Enterprise Edition v5.0 API Specifications

javax.servlet.jsp Class JspWriter

NO_BUFFER

DEFAULT_BUFFER

UNBOUNDED_BUFFER

bufferSize

autoFlush

JspWriter

newLine

print

print

print

print

print

print

print

print

print

println

println

println

println

println

println

println

println

println

println

clear

clearBuffer

flush

close

getBufferSize

getRemaining

isAutoFlush

javax.servlet.jsp
Class JspWriter