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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><!--NewPage--><HTML><HEAD><!-- Generated by javadoc (build 1.4.2_02) on Thu Nov 13 17:20:47 PST 2003 --><TITLE>JspWriter (Java 2 Platform Ent. Ed. v1.4)</TITLE><META NAME="keywords" CONTENT="javax.servlet.jsp.JspWriter class"><LINK REL ="stylesheet" TYPE="text/css" HREF="../../../stylesheet.css" TITLE="Style"><SCRIPT type="text/javascript">function windowTitle(){ parent.document.title="JspWriter (Java 2 Platform Ent. Ed. v1.4)";}</SCRIPT></HEAD><BODY BGCOLOR="white" onload="windowTitle();"><!-- ========= START OF TOP NAVBAR ======= --><A NAME="navbar_top"><!-- --></A><A HREF="#skip-navbar_top" title="Skip navigation links"></A><TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0" SUMMARY=""><TR><TD COLSPAN=3 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"><A NAME="navbar_top_firstrow"><!-- --></A><TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3" SUMMARY=""> <TR ALIGN="center" VALIGN="top"> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-summary.html"><FONT CLASS="NavBarFont1"><B>Package</B></FONT></A> </TD> <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Class</B></FONT> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../index-all.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../../help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> </TR></TABLE></TD><TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM><b>Java<sup><font size=-2>TM</font></sup> 2 Platform<br>Ent. Ed. v1.4</b></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../../javax/servlet/jsp/JspFactory.html" title="class in javax.servlet.jsp"><B>PREV CLASS</B></A> <A HREF="../../../javax/servlet/jsp/PageContext.html" title="class in javax.servlet.jsp"><B>NEXT CLASS</B></A></FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../../index.html" target="_top"><B>FRAMES</B></A> <A HREF="JspWriter.html" target="_top"><B>NO FRAMES</B></A> <SCRIPT type="text/javascript"> <!-- if(window==top) { document.writeln('<A HREF="../../../allclasses-noframe.html"><B>All Classes</B></A>'); } //--></SCRIPT><NOSCRIPT> <A HREF="../../../allclasses-noframe.html"><B>All Classes</B></A></NOSCRIPT></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: NESTED | <A HREF="#field_summary">FIELD</A> | <A HREF="#constructor_summary">CONSTR</A> | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: <A HREF="#field_detail">FIELD</A> | <A HREF="#constructor_detail">CONSTR</A> | <A HREF="#method_detail">METHOD</A></FONT></TD></TR></TABLE><A NAME="skip-navbar_top"></A><!-- ========= END OF TOP NAVBAR ========= --><HR><!-- ======== START OF CLASS DATA ======== --><H2><FONT SIZE="-1">javax.servlet.jsp</FONT><BR>Class JspWriter</H2><PRE><A HREF="http://java.sun.com/j2se/1.4/docs/api/java/lang/Object.html" title="class or interface in java.lang">java.lang.Object</A> <IMG SRC="../../../resources/inherit.gif" ALT="extended by"><A HREF="http://java.sun.com/j2se/1.4/docs/api/java/io/Writer.html" title="class or interface in java.io">java.io.Writer</A> <IMG SRC="../../../resources/inherit.gif" ALT="extended by"><B>javax.servlet.jsp.JspWriter</B></PRE><DL><DT><B>Direct Known Subclasses:</B> <DD><A HREF="../../../javax/servlet/jsp/tagext/BodyContent.html" title="class in javax.servlet.jsp.tagext">BodyContent</A></DD></DL><HR><DL><DT>public abstract class <B>JspWriter</B><DT>extends <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/io/Writer.html" title="class or interface in java.io">Writer</A></DL><P><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.<P><P><DL><DT><B>See Also:</B><DD><A HREF="http://java.sun.com/j2se/1.4/docs/api/java/io/Writer.html" title="class or interface in java.io"><CODE>Writer</CODE></A>, <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/io/BufferedWriter.html" title="class or interface in java.io"><CODE>BufferedWriter</CODE></A>, <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/io/PrintWriter.html" title="class or interface in java.io"><CODE>PrintWriter</CODE></A></DL><HR><P><!-- ======== NESTED CLASS SUMMARY ======== --><!-- =========== FIELD SUMMARY =========== --><A NAME="field_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Field Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected boolean</CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#autoFlush">autoFlush</A></B></CODE><BR> Whether the JspWriter is autoflushing.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected int</CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#bufferSize">bufferSize</A></B></CODE><BR> The size of the buffer used by the JspWriter.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static int</CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#DEFAULT_BUFFER">DEFAULT_BUFFER</A></B></CODE><BR> Constant indicating that the Writer is buffered and is using the implementation default buffer size.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static int</CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#NO_BUFFER">NO_BUFFER</A></B></CODE><BR> Constant indicating that the Writer is not buffering output.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>static int</CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#UNBOUNDED_BUFFER">UNBOUNDED_BUFFER</A></B></CODE><BR> Constant indicating that the Writer is buffered and is unbounded; this is used in BodyContent.</TD></TR></TABLE> <A NAME="fields_inherited_from_class_java.io.Writer"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor"><TD><B>Fields inherited from class java.io.<A HREF="http://java.sun.com/j2se/1.4/docs/api/java/io/Writer.html" title="class or interface in java.io">Writer</A></B></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><A HREF="http://java.sun.com/j2se/1.4/docs/api/java/io/Writer.html#lock" title="class or interface in java.io">lock</A></CODE></TD></TR></TABLE> <!-- ======== CONSTRUCTOR SUMMARY ======== --><A NAME="constructor_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Constructor Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>protected </CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#JspWriter(int, boolean)">JspWriter</A></B>(int bufferSize, boolean autoFlush)</CODE><BR> Protected constructor.</TD></TR></TABLE> <!-- ========== METHOD SUMMARY =========== --><A NAME="method_summary"><!-- --></A><TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY=""><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Method Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>abstract void</CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#clear()">clear</A></B>()</CODE><BR> Clear the contents of the buffer. </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>abstract void</CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#clearBuffer()">clearBuffer</A></B>()</CODE><BR> Clears the current contents of the buffer. </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>abstract void</CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#close()">close</A></B>()</CODE><BR> Close the stream, flushing it first. </TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE>abstract void</CODE></FONT></TD><TD><CODE><B><A HREF="../../../javax/servlet/jsp/JspWriter.html#flush()">flush</A></B>()</CODE><BR> Flush the stream. </TD>⌨️ 快捷键说明
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