javax.servlet.jsp.JspWriter Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package javax.servlet.jsp;
import java.io.IOException;
/**
*
* 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 java.io.Writer
* @see java.io.BufferedWriter
* @see java.io.PrintWriter
*/
abstract public class JspWriter extends java.io.Writer {
/**
* Constant indicating that the Writer is not buffering output.
*/
public static final int NO_BUFFER = 0;
/**
* Constant indicating that the Writer is buffered and is using the
* implementation default buffer size.
*/
public static final int DEFAULT_BUFFER = -1;
/**
* Constant indicating that the Writer is buffered and is unbounded; this is
* used in BodyContent.
*/
public static final int UNBOUNDED_BUFFER = -2;
/**
* Protected constructor.
*
* @param bufferSize
* the size of the buffer to be used by the JspWriter
* @param autoFlush
* whether the JspWriter should be autoflushing
*/
protected JspWriter(int bufferSize, boolean autoFlush) {
this.bufferSize = bufferSize;
this.autoFlush = autoFlush;
}
/**
* 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.
*
* @exception IOException
* If an I/O error occurs
*/
abstract public void newLine() throws IOException;
/**
* Print a boolean value. The string produced by {@link
* java.lang.String#valueOf(boolean)}
* is written to the JspWriter's buffer or, if no buffer is used, directly
* to the underlying writer.
*
* @param b
* The boolean to be printed
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void print(boolean b) 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.
*
* @param c
* The char to be printed
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void print(char c) throws IOException;
/**
* Print an integer. The string produced by {@link
* java.lang.String#valueOf(int)}
* is written to the JspWriter's buffer or, if no buffer is used, directly
* to the underlying writer.
*
* @param i
* The int to be printed
* @see java.lang.Integer#toString(int)
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void print(int i) throws IOException;
/**
* Print a long integer. The string produced by {@link
* java.lang.String#valueOf(long)}
* is written to the JspWriter's buffer or, if no buffer is used, directly
* to the underlying writer.
*
* @param l
* The long to be printed
* @see java.lang.Long#toString(long)
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void print(long l) throws IOException;
/**
* Print a floating-point number. The string produced by {@link
* java.lang.String#valueOf(float)}
* is written to the JspWriter's buffer or, if no buffer is used, directly
* to the underlying writer.
*
* @param f
* The float to be printed
* @see java.lang.Float#toString(float)
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void print(float f) throws IOException;
/**
* Print a double-precision floating-point number. The string produced by
* {@link java.lang.String#valueOf(double)} is written to the
* JspWriter's buffer or, if no buffer is used, directly to the underlying
* writer.
*
* @param d
* The double to be printed
* @see java.lang.Double#toString(double)
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void print(double d) 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.
*
* @param s
* The array of chars to be printed
* @throws NullPointerException
* If s is null
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void print(char 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.
*
* @param s
* The String to be printed
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void print(String s) throws IOException;
/**
* Print an object. The string produced by the {@link
* java.lang.String#valueOf(Object)}
* method is written to the JspWriter's buffer or, if no buffer is used,
* directly to the underlying writer.
*
* @param obj
* The Object to be printed
* @see java.lang.Object#toString()
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void print(Object obj) 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 java.io.IOException
* If an error occurred while writing
*/
abstract public void println() throws IOException;
/**
* Print a boolean value and then terminate the line. This method behaves as
* though it invokes {@link #print(boolean)} and then
* {@link #println()}.
*
* @param x
* the boolean to write
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void println(boolean x) throws IOException;
/**
* Print a character and then terminate the line. This method behaves as
* though it invokes {@link #print(char)} and then {@link
* #println()}
* .
*
* @param x
* the char to write
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void println(char x) throws IOException;
/**
* Print an integer and then terminate the line. This method behaves as
* though it invokes {@link #print(int)} and then {@link
* #println()}
* .
*
* @param x
* the int to write
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void println(int x) throws IOException;
/**
* Print a long integer and then terminate the line. This method behaves as
* though it invokes {@link #print(long)} and then
* {@link #println()}.
*
* @param x
* the long to write
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void println(long x) throws IOException;
/**
* Print a floating-point number and then terminate the line. This method
* behaves as though it invokes {@link #print(float)} and then
* {@link #println()}.
*
* @param x
* the float to write
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void println(float x) throws IOException;
/**
* Print a double-precision floating-point number and then terminate the
* line. This method behaves as though it invokes {@link
* #print(double)} and
* then {@link #println()}.
*
* @param x
* the double to write
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void println(double 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().
*
* @param x
* the char[] to write
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void println(char x[]) throws IOException;
/**
* Print a String and then terminate the line. This method behaves as though
* it invokes {@link #print(String)} and then
* {@link #println()}.
*
* @param x
* the String to write
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void println(String x) throws IOException;
/**
* Print an Object and then terminate the line. This method behaves as
* though it invokes {@link #print(Object)} and then
* {@link #println()}.
*
* @param x
* the Object to write
* @throws java.io.IOException
* If an error occurred while writing
*/
abstract public void println(Object x) 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
*/
abstract public void clear() 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
*/
abstract public void clearBuffer() 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.
*
* @exception IOException
* If an I/O error occurs
*/
@Override
abstract public void flush() 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.
*
* @exception IOException
* If an I/O error occurs
*/
@Override
abstract public void close() throws IOException;
/**
* This method returns the size of the buffer used by the JspWriter.
*
* @return the size of the buffer in bytes, or 0 is unbuffered.
*/
public int getBufferSize() {
return bufferSize;
}
/**
* This method returns the number of unused bytes in the buffer.
*
* @return the number of bytes unused in the buffer
*/
abstract public int getRemaining();
/**
* This method indicates whether the JspWriter is autoFlushing.
*
* @return if this JspWriter is auto flushing or throwing IOExceptions on
* buffer overflow conditions
*/
public boolean isAutoFlush() {
return autoFlush;
}
/*
* fields
*/
/**
* The size of the buffer used by the JspWriter.
*/
protected int bufferSize;
/**
* Whether the JspWriter is autoflushing.
*/
protected boolean autoFlush;
}