本篇是講述如何用特殊的tag寫一個(gè)可以讓java plugin辨認(rèn)的applet代碼的。哦，忘記說明了。所謂java plugin就是jre1.2（java runtime envirnment).客戶方只要安裝了它就可以運(yùn)行jdk1.2編寫的applet了。當(dāng)然，你的嵌入
applet的頁面必須按照本文所說的方式引用applet.就是用特殊的tag告訴瀏覽器：這是個(gè)jdk1.2的applet,請(qǐng)使用java plugin來解釋執(zhí)行它。我把它從SUN當(dāng)下來，在 166.111.4.80 和 ftp.cs.pku.edu.cn上各放了一份。
JAVATM PLUG-IN HTML SPECIFICATION
*Introduction
*JavaTM Plug-in in IE on Windows 95, Windows 98
or Windows NT 4.0 operating environments
*Java Plug-in in NavigatorTM on Windows 95,
Windows 98, Windows NT 4.0, or SolarisTM operating
environments
* Java Plug-in in IE and Navigator
* Java Plug-in Anywhere
* Summary
***Introduction
JavaTM Plug-in is a product from Sun Microsystems,
Inc. that runs beans or applets written in the Java
programming language in an HTML page using Sun's
Java virtual machine (JVM). To launch Java Plug-in
when IE or Netscape NavigatorTM browses an HTML
page, use the OBJECT tag and the EMBED tag in the
HTML specification.
This document explains the OBJECT tag and EMBED tag
styles required in Java Plug-in. It is intended for
users who want to manually insert Java Plug-in tags
in their HTML pages. There is a Java Plug-in HTML
Converter available free-of-charge from Sun Microsystems
that automatically does this for you.
The tag style described in this document has been
designed to work in the future when new browsers
are released on Windows 98, Windows NT 5.0 and
future versions of Solaris operating systems.
The information in this specification has been
tested on various platforms.
Details
Applets are in wide use today on the Internet.
They are normally specified in an HTML file as
follows:
<APPLET code="XYZApp.class" codebase="html/"
align="baseline" width="200" height="200">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET>
Normally, an APPLET tag specifies the information
about the applet and the <PARAM> tags between the
<APPLET> and </APPLET> tag store the per-instance
applet information.
Because an APPLET tag is rendered by the browser,
there is no easy way to interrupt the browser and
use Sun's JVM to run the applet. Instead, to use
Java Plug-in, you must use the Java Plug-in tag
(OBJECT or EMBED) in place of the APPLET tag in
an HTML page.
Java Plug-in in IE on Windows 95, Windows 98 or
Windows NT 4.0
To use Java Plug-in in IE on Windows 95, Windows
98 or Windows NT 4.0, use the OBJECT tag. The
following is an example of mapping an APPLET tag
to a Java Plug-in tag:
Original APPLET tag:
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET>
New OBJECT tag:
<OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width="200" height="200" align="baseline"
codebase="http://java.sun.com/products/plugin/1.2/
jinstall-12-win32.cab#Version=1,2,0,0">
<PARAM NAME="code" VALUE="XYZApp.class">
<PARAM NAME="codebase" VALUE="html/">
<PARAM NAME="type" VALUE="application/x-java-applet;version=1.2">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</OBJECT>
Note that the OBJECT tag contains similar information to
the APPLET tag. It is sufficient to launch Java Plug-in in
IE. The classid in the OBJECT tag is the class identifier
for Java Plug-in itself. This class identifier should be
the same in every HTML page. When IE renders this class
identifier in the OBJECT tag, it will try to load Java Plug-in
into the browser.
There are several attributes in the OBJECT tag, such as width,
height and align, that are mapped directly from the corresponding
attributes in the APPLET tag. These contain formatting information
that IE will use to position Java Plug-in. Since this information
is mapped directly without changes, the position and appearance of
the applets using Java Plug-in should be the same as those applets
using the APPLET tag.
Not all attributes in the APPLET tag can be mapped to the OBJECT
tag attributes. For example, the attributes code and codebase in
the APPLET tag are not mapped into the OBJECT tag attribute.
Instead, the attribute code is mapped into the PARAM code because,
according to the HTML specification, the attribute code does not
exist in the OBJECT tag. There are other attributes that do not
correspond in the OBJECT tag attributes. These attributes, with
one exception, should be mapped to PARAM tags.
The one exception is the codebase attribute. In the APPLET tag,
the codebase attribute represents the location from which to
download additional class and jar files. However, in the OBJECT
tag, the codebase attribute represents the location from which
to download Java Plug-in when it is not found on the local machine.
Because the codebase attribute has two different meanings in the
APPLET and OBJECT tags, you must resolve this conflict by mapping
this attribute into a PARAM codebase in the OBJECT tag.
In the above example, the code and codebase attributes in the APPLET
tag are mapped into the OBJECT tag parameters. The PARAM code
identifies the applet, and its value should be the same as the
code attribute in the APPLET tag. The PARAM codebase identifies
the codebase of the applet. Java Plug-in knows where to download
the applet or JavaBeans component because it can read this
information from the parameters. The parameter type is not
mapped from the APPLET tag, but it is required in the OBJECT tag.
It identifies the type of the Java executable, such as an applet
or a JavaBean, so Java Plug-in knows how to initialize the Java
executable. These three PARAM tags (code, codebase, and type) in
the above example are specified by Java Plug-in. They do not exist
in the PARAM of the original APPLET tag. Note that the model
parameter within the OBJECT tag is identical to the model parameter
inside the APPLET tag. Except for these first three parameters
specified for Java Plug-in, the remainder of the parameters are
the same as those inside the APPLET tag.
The text "No JDK 1.2 support for APPLET!!" in the APPLET tag is
mapped inside the <OBJECT> and </OBJECT> tags. Originally, this
text is displayed only if the browser does not have Java support.
By mapping it inside the OBJECT tag, this text will displayed if
the browser does not support the OBJECT tag.
The APPLET-OBJECT tag attributes mapping is as follows:
Attributes APPLET tag support OBJECT tag support Attribute map
in OBJECT tag
ALIGN X X Attribute ALIGN
ALT X
ARCHIVE X Param archive
CODE X X Param code
CODEBASE X X Param codebase
HEIGHT X X Attribute HEIGHT
HSPACE X X Attribute HSPACE
NAME X X Attribute NAME, Param NAME
OBJECT X Param object
TITLE X X Attribute TITLE
VSPACE X X Attribute VSPACE
WIDTH X X Attribute WIDTH
MAYSCRIPT X X Param MAYSCRIPT
Some attributes are special to the OBJECT tag. These
attributes are:
Meaning in OBJECT tag
Attribute CLSID It should always have the same value.
i.e. "clsid:8AD9C840-044E-11D1-B3E9-00805F499D93".
Attribute CODEBASE It should be a full URL pointing to a
CAB file somewhere on the network. It should, by default,
point to a page on the Java Software web site.
Param type If it is a Java applet, the value should be
"application/x-java-applet;version=1.2" or "application/x-java-applet".
If it is a JavaBeans component, the value should be
"application/x-java-bean;version=1.2" or "application/x-java-bean".
Param codebase Specifies the base URL of the applet. Relative URL
to the document should be used. This attribute is optional.
Param code Specifies the name of the Java applet or JavaBeans component.
It cannot be used with param object inside the same OBJECT tag.
Param object Specifies the name of the serialized Java applet or
JavaBeans component. It cannot be used with param code inside the
same OBJECT tag. This attribute is optional. Param archive Specifies
the name of the Java archive. This attribute is optional.
Param mayscript Specifies whether the applet is allowed to access
netscape.javascript.JSObject. The value can be either "true" or
"false". This attribute is optional.
Note that if the original APPLET tag has PARAM type, codebase,
code, object or archive, mapping it to the OBJECT tag will
cause a problem because duplicate param names will occur.
To avoid this, Java Plug-in also supports another set of param
names, as follows:
Original Param Names New Param Names
code java_code
codebase java_codebase
archive java_archive
object java_object
type java_type
You should use these new param names only when necessary.
If both the new and original param names exist in the same
OBJECT tag, the value associated with the new param name
is always used by Java Plug-in to load the applet or JavaBean.
Java Plug-in in Netscape Navigator on Windows 95, Windows
98, Windows NT 4.0, or SolarisTM operating environments
To use Java Plug-in in Netscape Navigator 3 or 4 on
Windows 95, Windows 98, Windows NT 4.0, or Solaris operating
environments, use the EMBED tag. The following example maps
an APPLET tag to a Java Plug-in EMBED tag:
Original APPLET tag:
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET>
New EMBED tag:
<EMBED type="application/x-java-applet;version=1.2" width="200"
height="200" align="baseline" code="XYZApp.class"
codebase="html/" model="models/HyaluronicAcid.xyz"
pluginspage="http://java.sun.com/products/plugin/1.2/plugin-install.html">
<NOEMBED>
No JDK 1.2 support for APPLET!!
</NOEMBED>
</EMBED>
Note that the EMBED tag contains similar information to the APPLET
tag, and it is sufficient to launch Java Plug-in in Navigator. The
attribute type in the EMBED tag is used for identifying the type of
the Java programming language executable, such as an applet or a
bean. When Navigator renders this attribute in the EMBED tag, it
will try to load Java Plug-in into the browser. By specifying the
type attribute, Java Plug-in will know how to initialize the Java
programming language executable.
In the above example, several attributes in the EMBED tag, such
as width, height and align, map directly from the corresponding
attributes in the APPLET tag. These contain formatting information
that Navigator uses to position Java Plug-in. Since this information
is mapped directly without changes, the position and appearance of
the applets using Java Plug-in should be the same as those applets
using the APPLET tag.
Unlike the OBJECT tag, all information must be stored inside the
<EMBED> tag instead of using PARAM. Therefore, all attributes and
params in the APPLET tag must be mapped as attribute-value pairs
inside the EMBED tag.
In the above example, the code and codebase attributes in the
APPLET tag are mapped into the EMBED tag attributes. Attribute
code identifies the applet. Its value should be the same as the
code attribute in the APPLET tag. Attribute codebase identifies
the codebase of the applet. Java Plug-in knows where to download
the applet or JavaBeans component because it can read this
information from the attributes. Also notice that the model
attribute within the EMBED tag is mapped from the model param
inside the APPLET tag.
Like the codebase attribute in the OBJECT tag, attribute
pluginspage in the EMBED tag is used by Navigator if Java
Plug-in is not installed. It should always point to the Java
Plug-in Download Page on the Java Software web site.
The text "No JDK 1.2 support for APPLET!!" in the APPLET tag
is mapped inside the <NOEMBED> and </NOEMBED> tags. Originally,
this text is displayed only if the browser does not have Java
technology support. By mapping it inside the NOEMBED tag, this
text will be displayed if the browser does not support the EMBED
tag or if Navigator fails to start the Java Plug-in.
The APPLET-EMBED tag attributes mapping is as follows:
Attributes APPLET tag support EMBED tag support Attribute map in EMBED tag
ALIGN X X Attribute ALIGN
ALT X X Attribute ALT
ARCHIVE X Attribute archive
CODE X Attribute code
CODEBASE X Attribute codebase
HEIGHT X X Attribute HEIGHT
HSPACE X X Attribute HSPACE
NAME X X Attribute NAME
OBJECT X Attribute object
TITLE X X Attribute TITLE
VSPACE X X Attribute VSPACE
WIDTH X X Attribute WIDTH
MAYSCRIPT X X Attribute MAYSCRIPT
Some attributes are special to the EMBED tag. These attributes are:
Meaning in EMBED tag
Attribute type If it is an applet, the value should be
"application/x-java-applet;version=1.2" or "application/x-java-applet".
If it is a bean, the value should be
"application/x-java-bean;version=1.2" or "application/x-java-bean".
Attribute codebase Specifies the base URL of the applet.
This attribute is optional.
Attribute code Specifies the name of the Java applet or JavaBeans
component. It cannot be used with param object inside the same
EMBED tag.
Attribute object Specifies the name of the serialized Java applet
or JavaBeans component. It cannot be used with param code inside
the same EMBED tag. This attribute is optional.
Attribute archive Specifies the name of the Java archive.
This attribute is optional.
Attribute pluginspage It should be a full URL pointing to an
HTML page somewhere on the network.
Attribute mayscript Specifies whether the applet is allowed to
access netscape.javascript.JSObject. The value can be either
"true" or "false". This attribute is optional.
Similar to the OBJECT tag case, if the original APPLET tag
has PARAM type, codebase, code, object, or archive, mapping
it to the EMBED tag attribute will cause a problem. To avoid
this, Java Plug-in also supports the same new set of attribute
names, as follows:
Original Attribute Names New Attribute Names
code java_code
codebase java_codebase
archive java_archive
object java_object
type java_type
You should use these new attribute names only necessary.
If both new and original attribute names exist in the same
EMBED tag, the value associated with the new attribute name
is always used by Java Plug-in to load the applet or bean.
Java Plug-in in IE and Navigator
The OBJECT tag in IE and the EMBED tag in Navigator allows
your HTML page to use Java Plug-in if the HTML page is browsed
on Windows 95, Windows 98, Windows NT 4.0, or Solaris operating
environments. However, if the HTML page is on the Internet/intranet,
the page is likely to be browsed by both IE and Navigator.
You should activate the Java Plug-in if both Navigator and
IE will browse the same HTML page. You can do this using the
Java Plug-in OBJECT tag, as follows:
Original APPLET tag:
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET>
New OBJECT tag:
<OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width="200" height="200" align="baseline"
codebase="http://java.sun.com/products/plugin/1.2/
jinstall-12-win32.cab#Version=1,2,0,0">
<PARAM NAME="code" VALUE="XYZApp.class">
<PARAM NAME="codebase" VALUE="html/">
<PARAM NAME="type" VALUE="application/x-java-applet;version=1.2">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
<COMMENT>
<EMBED type="application/x-java-applet;version=1.2" width="200"
height="200" align="baseline" code="XYZApp.class"
codebase="html/" model="models/HyaluronicAcid.xyz"
pluginspage="http://java.sun.com/products/plugin/1.2/
plugin-install.html">
<NOEMBED>
</COMMENT>
No JDK 1.2 support for APPLET!!
</NOEMBED></EMBED>
</OBJECT>
Because IE understands the <OBJECT> tag, it will try to
launch Java Plug-in. Notice that the <COMMENT> tag is a
special HTML tag understood only by IE. IE ignores text
between the <COMMENT> and </COMMENT> tags. In effect, the
above tags actually become:
<OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width="200" height="200" align="baseline"
codebase="http://java.sun.com/products/plugin/1.2/
jinstall-12-win32.cab#Version=1,2,0,0">
<PARAM NAME="code" VALUE="XYZApp.class">
<PARAM NAME="codebase" VALUE="html/">
<PARAM NAME="type" VALUE="application/x-java-applet;version=1.2">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</NOEMBED></EMBED>
</OBJECT>
This is identical to the OBJECT tag example outlined above.
The </NOEMBED> and </EMBED> tags are ignored by the OBJECT tag
because there are no corresponding <NOEMBED> and <EMBED> tags.
Because Navigator does not understand the OBJECT and COMMENT
tags, Navigator 3/4 on the Windows 95, Windows 98, Windows NT
4.0, or Solaris operating environments reads the above tags
as follows:
<EMBED type="application/x-java-applet;version=1.2" width="200" height="200"
align="baseline" code="XYZApp.class" codebase="html/"
model="models/HyaluronicAcid.xyz"
pluginspage="http://java.sun.com/products/plugin/1.2/plugin-install.html">
<NOEMBED>
No JDK 1.2 support for APPLET!!
</NOEMBED>
</EMBED>
This is identical to the EMBED tag example outlined above.
Navigator 3/4 ignores <COMMENT> and </COMMENT> tags because
they are an HTML extension in IE only.
This example illustrates that you can use the combined
OBJECT-EMBED tag to activate Java Plug-in in the browser
if either IE or Navigator is used. This combined tag is strongly
recommended unless your HTML page is browsed by users in a
homogeneous environment. The Java Plug-in HTML Converter from
Sun Microsystems automatically converts HTML pages into this
tag style for you.
Java Plug-in Anywhere
In an Internet/intranet environment, an HTML page is likely to
be seen by browsers on different platforms. You should activate
Java Plug-in only on the right browser and platform combination.
Otherwise, you should use the browser's default JVM. You can
achieve this using the following Java Plug-in tag:
Original APPLET tag:
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET>
New style tag:
The following is an example of an equivalent Java Plug-in tag.
This example includes comments.
<!-- The following code is specified at the beginning of the <BODY> tag. -->
<SCRIPT LANGUAGE="JavaScript"><!--
var _info = navigator.userAgent; var _ns = false;
var _ie = (_info.indexOf("MSIE") > 0 && _info.indexOf("Win") > 0
&& _info.indexOf("Windows 3.1") < 0);
//--></SCRIPT>
<COMMENT><SCRIPT LANGUAGE="JavaScript1.1"><!--
var _ns = (navigator.appName.indexOf("Netscape") >= 0
&& ((_info.indexOf("Win") > 0 && _info.indexOf("Win16") < 0
&& java.lang.System.getProperty("os.version").indexOf("3.5") < 0)
|| _info.indexOf("Sun") > 0));
//--></SCRIPT></COMMENT>
<!-- The following code is repeated for each APPLET tag -->
<SCRIPT LANGUAGE="JavaScript"><!--
if (_ie == true) document.writeln('
<OBJECT
classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width="200" height="200" align="baseline"
codebase="http://java.sun.com/products/plugin/1.2/
jinstall-12-win32.cab#Version=1,2,0,0">
<NOEMBED><XMP>');
else if (_ns == true) document.writeln('
<EMBED
type="application/x-java-applet;version=1.2" width="200" height="200"
align="baseline" code="XYZApp.class" codebase="html/"
model="models/HyaluronicAcid.xyz"
pluginspage="http://java.sun.com/products/plugin/1.2/plugin-install.html">
<NOEMBED><XMP>');
//--></SCRIPT>
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200">
</XMP>
<PARAM NAME="java_code" VALUE="XYZApp.class">
<PARAM NAME="java_codebase" VALUE="html/">
<PARAM NAME="java_type" VALUE="application/x-java-applet;version=1.2">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET></NOEMBED></EMBED>
</OBJECT>
<!--
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET>
-->
Although this tag seems complicated compared to the old APPLET
tag, it is not. Most of the Java Plug-in tag is the same regardless
of the applet used. For the majority of cases, a webmaster can copy
and paste the Java Plug-in tag.
The first block of the script extracts the browser and platform. You
must determine the browser and platform on which the applet is running.
You do this by using JavaScriptTM to extract first the browser name,
then the platform. This is done once per HTML document.
The second block of the script replaces the APPLET tag. You must
replace each APPLET tag with a similar block of code. The script
replaces the APPLET tag with either an EMBED tag or OBJECT tag,
depending on the browser. You use the OBJECT tag for IE and the
EMBED tag for Netscape Navigator. Finally, the original APPLET tag
is included as a comment at the end. It is always a good idea to
keep the original APPLET tag in case you want to remove the Java
Plug-in invocation.
The first JavaScript establishes the browser and the platform on
which the browser is running. You must do this because, currently,
Java Plug-in supports only Windows 95, Windows 98, Windows NT 4.0,
and Solaris. Note that Windows NT 3.51 is the only Win32 platform
that Java Plug-in does not support. Java Plug-in should be invoked
only on the supported browser and platform. The script sets the
variable _ie to true if the browser is Internet Explorer. It sets
the variable _ns to true if the browser is Navigator. (Note that
all variable names in the JavaScript start with "_". This is done
to avoid conflicting with other JavaScript variables in the same
page.)
To detect the right browser, the JavaScript evaluates three strings
that are within the JavaScript's Navigator object: userAgent,
appVersion, and appName. These strings contain information about
the browser and the platform. By looking at some examples of the
string userAgent, you can see how to evaluate userAgent and use it
to determine the browser. The following are some examples of the
userAgent string for different platforms as it appears in Internet
Explorer.
Platform and Browser JavaScript's Navigator.userAgent string
Windows NT 4.0 w/IE 4.0 "Mozilla/4.0 (compatible; MSIE 4.0; Windows NT)"
Windows NT 4.0 w/IE 3.02 "Mozilla/2.0 (compatible; MSIE 3.02; Windows NT)"
Windows 95 w/IE 4.0 "Mozilla/4.0 (compatible; MSIE 4.0; Windows 95)"
Windows 95 w/IE 3.02 "Mozilla/2.0 (compatible; MSIE 3.02; Windows 95)"
Windows NT 3.51 w/IE 4.0 "Mozilla/4.0 (compatible; MSIE 4.0; Windows 3.1)"
Windows 3.1 w/IE 4.0 "Mozilla/4.0 (compatible; MSIE 4.0; Windows 3.1)"
Windows NT 4.0 w/Navigator 4.04 "Mozilla/4.04 [en] (WinNT; I)"
Windows NT 4.0 w/Navigator 3.04 "Mozilla/3.04 (WinNT; I)"
Windows NT 3.51 w/Navigator 4.04 "Mozilla/4.04 [en] (WinNT; I)"
Windows NT 3.51 w/Navigator 3.04 "Mozilla/3.04 (WinNT; I)"
Windows 95 w/Navigator 4.03 "Mozilla/4.03 [en] (Win95; I)"
Windows 95 w/Navigator 3.03 "Mozilla/3.03 (Win95; I)"
Solaris 2.6 w/Navigator 4.02 "Mozilla/4.02 [en] (X11; l; SunOS 5.6 sun4u)
/* 此處刪去了一個(gè)表格。 */
The above table shows that only Windows 95 and Windows NT 4.0 with IE
can pass the Java Plug-in browser and platform requirements. However,
this logic makes no assumptions about future releases of IE or future
releases of Windows with IE. As long as the userAgent string contains
"MSIE" and "Win", the above code should work in future releases of
IE on Win32.
The above logic summarizes into the following:
<SCRIPT LANGUAGE="JavaScript"><!--
var _info = navigator.userAgent;
var _ie = (_info.indexOf("MSIE") > 0 && _info.indexOf("Win") > 0
&& _info.indexOf("Windows 3.1") < 0);
//--></SCRIPT>
It is harder to detect Navigator on the right platform. Using just
JavaScript, there is no way to determine if the browser is running
on the Windows NT 3.51 or Windows NT 4.0 operating platform. (Refer
to the above table and examine the userAgent string. Notice that
the userAgent strings in Windows NT 3.51 and Windows NT 4.0 operating
platforms are the same in Navigator.) It is important to make this
distinction because Java Plug-in supports only the Windows NT 4.0
operating platform. To run Java Plug-in on the right platform, you
must use LiveConnect in Navigator to determine the OS version number.
This can be summarized as follows:
/* 此處刪去一個(gè)表格。*/
The above logic translates into the following code:
<SCRIPT LANGUAGE="JavaScript"><!--
var _info = navigator.userAgent; var _ns = false;
//--></SCRIPT>
<COMMENT><SCRIPT LANGUAGE="JavaScript1.1"><!--
var _ns = (navigator.appName.indexOf("Netscape") >= 0
&& ((_info.indexOf("Win") > 0 && _info.indexOf("Win16") < 0
&& java.lang.System.getProperty("os.version").indexOf("3.5") < 0)
|| _info.indexOf("Sun") > 0));
//--></SCRIPT></COMMENT>
Referring to the previous table, note that only Windows 95, Windows NT
4.0, and Solaris operating environments with Navigator pass all the tests.
Because LiveConnect is used to get the OS version number and only Navigator
supports LiveConnect, a JavaScript that accesses LiveConnect will not be
understood by IE. To prevent this from causing a problem, you block out
this piece of the script using the COMMENT tag since COMMENT is an
IE-specific comment tag. The text between the COMMENT tag is ignored
by IE but not by Navigator. In addition, you must specify the script
language as JavaScript1.1 to block this out if the browser is Navigator 2.
At this point, the above logic for IE and Navigator summarizes to a script
that should look as follows:
<!-- The following code is specified at the beginning of the <BODY> tag. -->
<SCRIPT LANGUAGE="JavaScript"><!--
var _info = navigator.userAgent; var _ns = false;
var _ie = (_info.indexOf("MSIE") > 0 && _info.indexOf("Win") > 0
&& _info.indexOf("Windows 3.1") < 0);
//--></SCRIPT>
<COMMENT><SCRIPT LANGUAGE="JavaScript1.1"><!--
var _ns = (navigator.appName.indexOf("Netscape") >= 0
&& ((_info.indexOf("Win") > 0 && _info.indexOf("Win16") < 0
&& java.lang.System.getProperty("os.version").indexOf("3.5") < 0)
|| _info.indexOf("Sun") > 0));
//--></SCRIPT></COMMENT>
Remember that this block of JavaScript should be put at the top of the
<BODY> of the HTML file. It is put at the top so that other JavaScripts
can reference the variables _ie and _ns. This JavaScript is the same in
all HTML files, and it is only needed once for each HTML body.
The second block of HTML tags are actually the corresponding OBJECT
and EMBED tags that are mapped from the data in the APPLET tag. Note
that JavaScript outputs the OBJECT tag when the browser is IE running
on the Windows 95, Windows 98 or Windows NT 4.0 operating environments.
If the browser is Navigator 3/4 on Windows 95, Windows 98, Windows NT
4.0, or Solaris operating environments, then JavaScript also outputs
the EMBED tag, though with a slightly different syntax. Recall that the
mechanism for detecting the browser and the platform has been described
in the above section. (Tags <!-- and --> are used for comments in HTML.)
Original APPLET tag:
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET>
New style tag:
<SCRIPT LANGUAGE="JavaScript"><!--
if (_ie == true) document.writeln('<OBJECT
classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width="200" height="200" align="baseline"
codebase="http://java.sun.com/products/plugin/1.2/
jinstall-12-win32.cab#Version=1,2,0,0">
<NOEMBED><XMP>');
else if (_ns == true) document.writeln('<EMBED
type="application/x-java-applet;version=1.2" width="200" height="200"
align="baseline" code="XYZApp.class" codebase="html/"
model="models/HyaluronicAcid.xyz"
pluginspage="http://java.sun.com/products/plugin/1.2/plugin-install.html">
<NOEMBED><XMP>');
//--></SCRIPT>
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200"></XMP>
<PARAM NAME="java_code" VALUE="XYZApp.class">
<PARAM NAME="java_codebase" VALUE="html/">
<PARAM NAME="java_type" VALUE="application/x-java-applet;version=1.2">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET></NOEMBED></EMBED></OBJECT>
Note that the original APPLET tag is also mapped in the new Java
Plug-in tag. This is done because Java Plug-in is intended to be used
only on supported platforms. Leaving the APPLET tag in the script
ensures that browsers that do not support Java Plug-in, or browsers
that do not support JavaScript can gracefully handle the applet using
the default JVM. HotJava Browser, IE, and Navigator on non-Java Plug-in
supported platforms, or browsers without JavaScript support, read the
above tags as follows:
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200"></XMP>
<PARAM NAME="java_code" VALUE="XYZApp.class">
<PARAM NAME="java_codebase" VALUE="html/">
<PARAM NAME="java_type" VALUE="application/x-java-applet;version=1.2">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET></NOEMBED></EMBED></OBJECT>
These browsers ignore the tags </XMP>, </OBJECT>, </EMBED>, and
</NOEMBED> as well because there is no corresponding <XMP>, <OBJECT>,
<EMBED>, and <NOEMBED> tags. Because Java Plug-in is targeted for
features in the JDK 1.2 or future releases, those browsers without
full JDK 1.2 support and who do not support Java Plug-in will display
the message "No JDK 1.2 support for APPLET".
Unlike the previous examples, the mapped PARAM names contain java_code,
java_codebase, and java_type instead of code, codebase, and type. This
is necessary because specifying code and codebase in the <PARAM> inside
the <APPLET> and </APPLET> tag causes problems in some browsers.
IE on Windows 95, Windows 98 or Windows NT 4.0 reads the tags as follows:
<OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width="200" height="200" align="baseline"
codebase="http://java.sun.com/products/plugin/1.2/
jinstall-12-win32.cab#Version=1,2,0,0">
<NOEMBED><XMP>
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200"></XMP>
<PARAM NAME="java_code" VALUE="XYZApp.class">
<PARAM NAME="java_codebase" VALUE="html/">
<PARAM NAME="java_type" VALUE="application/x-java-applet;version=1.2">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET></NOEMBED></EMBED>
</OBJECT>
Be careful when you use the <XMP> tag. Because IE renders the <OBJECT>
tag, you must disable the <APPLET> tag. If not disabled, two applets
will simultaneously show up in the browser--one applet will be running
in Microsoft's JVM, and the other will be running in Sun's JVM using
Java Plug-in. The <XMP> tag provides a solution. The <XMP> and </XMP>
tags basically transform any HTML tag that occurs between them into a
stream of static text. In the above example, the <XMP> and </XMP> tags
cause the browser to treat the <APPLET> tag as static text instead of
an HTML tag. Because the browser ignores any static text between the
<OBJECT> tag and the <PARAM> tag, the above tags actually become:
<OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width="200" height="200" align="baseline"
codebase="http://java.sun.com/products/plugin/1.2/
jinstall-12-win32.cab#Version=1,2,0,0">
<PARAM NAME="java_code" VALUE="XYZApp.class">
<PARAM NAME="java_codebase" VALUE="html/">
<PARAM NAME="java_type" VALUE="application/x-java-applet;version=1.2">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</OBJECT>
This is identical to the OBJECT tag example outlined above. Note that
the <OBJECT> tag ignores the <NOEMBED>, </NOEMBED>, and </EMBED> tags.
Navigator 3/4 on Windows 95, Windows 98 or Windows NT 4.0 operating
environments reads tags as follows:
<EMBED type="application/x-java-applet;version=1.2" width="200" height="200"
align="baseline" code="XYZApp.class" codebase="html/"
model="models/HyaluronicAcid.xyz"
pluginspage="http://java.sun.com/products/plugin/1.2/plugin-install.html">
<NOEMBED><XMP>
<APPLET code="XYZApp.class" codebase="html/" align="baseline"
width="200" height="200"></XMP>
<PARAM NAME="java_code" VALUE="XYZApp.class">
<PARAM NAME="java_codebase" VALUE="html/">
<PARAM NAME="java_type" VALUE="application/x-java-applet;version=1.2">
<PARAM NAME="model" VALUE="models/HyaluronicAcid.xyz">
No JDK 1.2 support for APPLET!!
</APPLET></NOEMBED></EMBED></OBJECT>
Note that the <XMP> tag is used again in the <EMBED> tag to also
disable the <APPLET> tag. The <EMBED> tag ignores the <PARAM> and
</OBJECT> tags as well. In effect, the above tags actually become:
<EMBED type="application/x-java-applet;version=1.2" width="200" height="200"
align="baseline" code="XYZApp.class" codebase="html/"
model="models/HyaluronicAcid.xyz"
pluginspage="http://java.sun.com/products/plugin/1.2/plugin-install.html">
<NOEMBED>
No JDK 1.2 support for APPLET!!
</NOEMBED>
</EMBED>
This is identical to the EMBED tag example outlined above.
You can use the combined OBJECT-EMBED-JavaScript tag to activate Java Plug-in
in the right browser on the right platform. This combined tag is complicated
and it should be used only if your HTML page is browsed by users in a
heterogenous environment.
Summary
This document describes the OBJECT tag and EMBED tag styles used by Java
Plug-in. It focuses on the conversion from an APPLET tag to the OBJECT
and EMBED tags. Currently, HTML 4.0 suggests that the OBJECT tag is the
best way to insert Java applets and JavaBeans components into a HTML page.
This document will be updated in the near future should there be a need to
convert the OBJECT tag to the Java Plug-in tag style. Information disclosed
in this document is intended to assist ISVs for writing HTML migration tools
and to assist webmasters with Java Plug-in migration. The tag style described
in this document is subject to change in the future.
Note that the use of Java Plug-in is not limited to the tag styles described
in this document. In fact, webmasters are encouraged to modify the tag style
or mix the tag with JavaScript to fit their needs. As long as the described
OBJECT tag is used in IE and EMBED tag is used in Navigator, there should be
no problems running Java Plug-in. Currently, there are several conversion
templates shipped with the Java Plug-in HTML converter. Webmasters may find
one template better than others for their needs, and are encouraged to
modify these templates themselves if necessary.
凡是有該標(biāo)志的文章，都是該blog博主Caoer（草兒）原創(chuàng)，凡是索引、收藏
、轉(zhuǎn)載請(qǐng)注明來處和原文作者。非常感謝。