JspWriter (Apache Tomcat 7.0.109 API Documentation)

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

All Implemented Interfaces:

Closeable, Flushable, Appendable, AutoCloseable

Direct Known Subclasses:

BodyContent, JspWriterImpl
```
public abstract class JspWriter
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

Fields
Modifier and Type	Field and Description
`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

Constructors
Modifier Constructor and Description

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

Constructors
Modifier	Constructor and Description
`protected`	`JspWriter(int bufferSize, boolean autoFlush)` Protected constructor.

Method Summary

Methods
Modifier and Type	Method and Description
`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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 occurred 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 interface AutoCloseable
    
    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

Class JspWriter

Field Summary

Fields inherited from class java.io.Writer

Constructor Summary

Method Summary

Methods inherited from class java.io.Writer

Methods inherited from class java.lang.Object

Field Detail

NO_BUFFER

DEFAULT_BUFFER

UNBOUNDED_BUFFER

bufferSize

autoFlush

Constructor Detail

JspWriter

Method Detail

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