| /* |
| * Copyright 2004 The Apache Software Foundation |
| * |
| * Licensed 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; |
| |
| /** |
| * <p> |
| * 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. |
| *<p> |
| * 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. |
| * <p><B>Buffering</B> |
| * <p> |
| * 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. |
| * <p> |
| * Buffering raises the issue of what to do when the buffer is |
| * exceeded. Two approaches can be taken: |
| * <ul> |
| * <li> |
| * Exceeding the buffer is not a fatal error; when the buffer is |
| * exceeded, just flush the output. |
| * <li> |
| * Exceeding the buffer is a fatal error; when the buffer is exceeded, |
| * raise an exception. |
| * </ul> |
| * <p> |
| * 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. |
| * <p> |
| * 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. |
| * <p> |
| * 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 <tt>line.separator</tt>, 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 <code>{@link |
| * java.lang.String#valueOf(boolean)}</code> is written to the |
| * JspWriter's buffer or, if no buffer is used, directly to the |
| * underlying writer. |
| * |
| * @param b The <code>boolean</code> to be printed |
| * @throws java.io.IOException If an error occured 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 <code>char</code> to be printed |
| * @throws java.io.IOException If an error occured while writing |
| */ |
| |
| abstract public void print(char c) throws IOException; |
| |
| /** |
| * Print an integer. The string produced by <code>{@link |
| * java.lang.String#valueOf(int)}</code> is written to the |
| * JspWriter's buffer or, if no buffer is used, directly to the |
| * underlying writer. |
| * |
| * @param i The <code>int</code> to be printed |
| * @see java.lang.Integer#toString(int) |
| * @throws java.io.IOException If an error occured while writing |
| */ |
| |
| abstract public void print(int i) throws IOException; |
| |
| /** |
| * Print a long integer. The string produced by <code>{@link |
| * java.lang.String#valueOf(long)}</code> is written to the |
| * JspWriter's buffer or, if no buffer is used, directly to the |
| * underlying writer. |
| * |
| * @param l The <code>long</code> to be printed |
| * @see java.lang.Long#toString(long) |
| * @throws java.io.IOException If an error occured while writing |
| */ |
| |
| abstract public void print(long l) throws IOException; |
| |
| /** |
| * Print a floating-point number. The string produced by <code>{@link |
| * java.lang.String#valueOf(float)}</code> is written to the |
| * JspWriter's buffer or, if no buffer is used, directly to the |
| * underlying writer. |
| * |
| * @param f The <code>float</code> to be printed |
| * @see java.lang.Float#toString(float) |
| * @throws java.io.IOException If an error occured while writing |
| */ |
| |
| abstract public void print(float f) throws IOException; |
| |
| /** |
| * Print a double-precision floating-point number. The string produced by |
| * <code>{@link java.lang.String#valueOf(double)}</code> is written to |
| * the JspWriter's buffer or, if no buffer is used, directly to the |
| * underlying writer. |
| * |
| * @param d The <code>double</code> to be printed |
| * @see java.lang.Double#toString(double) |
| * @throws java.io.IOException If an error occured 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 <code>s</code> is <code>null</code> |
| * @throws java.io.IOException If an error occured while writing |
| */ |
| |
| abstract public void print(char s[]) throws IOException; |
| |
| /** |
| * Print a string. If the argument is <code>null</code> then the string |
| * <code>"null"</code> 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 <code>String</code> to be printed |
| * @throws java.io.IOException If an error occured while writing |
| */ |
| |
| abstract public void print(String s) throws IOException; |
| |
| /** |
| * Print an object. The string produced by the <code>{@link |
| * java.lang.String#valueOf(Object)}</code> method is written to the |
| * JspWriter's buffer or, if no buffer is used, directly to the |
| * underlying writer. |
| * |
| * @param obj The <code>Object</code> to be printed |
| * @see java.lang.Object#toString() |
| * @throws java.io.IOException If an error occured 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 |
| * <code>line.separator</code>, and is not necessarily a single newline |
| * character (<code>'\n'</code>). |
| * @throws java.io.IOException If an error occured while writing |
| */ |
| |
| abstract public void println() throws IOException; |
| |
| /** |
| * Print a boolean value and then terminate the line. This method behaves |
| * as though it invokes <code>{@link #print(boolean)}</code> and then |
| * <code>{@link #println()}</code>. |
| * |
| * @param x the boolean to write |
| * @throws java.io.IOException If an error occured 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 <code>{@link #print(char)}</code> and then <code>{@link |
| * #println()}</code>. |
| * |
| * @param x the char to write |
| * @throws java.io.IOException If an error occured 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 <code>{@link #print(int)}</code> and then <code>{@link |
| * #println()}</code>. |
| * |
| * @param x the int to write |
| * @throws java.io.IOException If an error occured 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 <code>{@link #print(long)}</code> and then |
| * <code>{@link #println()}</code>. |
| * |
| * @param x the long to write |
| * @throws java.io.IOException If an error occured 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 <code>{@link #print(float)}</code> and then |
| * <code>{@link #println()}</code>. |
| * |
| * @param x the float to write |
| * @throws java.io.IOException If an error occured 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 <code>{@link |
| * #print(double)}</code> and then <code>{@link #println()}</code>. |
| * |
| * @param x the double to write |
| * @throws java.io.IOException If an error occured 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 <code>print(char[])</code> and then |
| * <code>println()</code>. |
| * |
| * @param x the char[] to write |
| * @throws java.io.IOException If an error occured 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 <code>{@link #print(String)}</code> and then |
| * <code>{@link #println()}</code>. |
| * |
| * @param x the String to write |
| * @throws java.io.IOException If an error occured 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 <code>{@link #print(Object)}</code> and then |
| * <code>{@link #println()}</code>. |
| * |
| * @param x the Object to write |
| * @throws java.io.IOException If an error occured 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. |
| * <p> |
| * The method may be invoked indirectly if the buffer size is exceeded. |
| * <p> |
| * 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 |
| */ |
| |
| abstract public void flush() throws IOException; |
| |
| /** |
| * Close the stream, flushing it first. |
| * <p> |
| * 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(). |
| * <p> |
| * Closing a previously-closed stream, unlike flush(), has no effect. |
| * |
| * @exception IOException If an I/O error occurs |
| */ |
| |
| 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; |
| } |