{"id":15,"date":"2006-08-18T17:45:00","date_gmt":"2006-08-18T17:45:00","guid":{"rendered":"http:\/\/euve3303.vserver.de\/stefan\/blog\/?p=17"},"modified":"2011-12-01T20:41:06","modified_gmt":"2011-12-01T19:41:06","slug":"swt-applikation-als-applet","status":"publish","type":"post","link":"https:\/\/cogito-ergo-blog.de\/blog\/2006\/08\/18\/swt-applikation-als-applet\/","title":{"rendered":"SWT Applikation als Applet"},"content":{"rendered":"

[:de]Neulich stellte sich mir die Frage, warum eigentlich nicht auch SWT Applikationen als Applet laufen k\u00f6nnen. Gut der erste Grund ist sicherlich, dass SWT nicht immer installiert ist, im Gegensatz zu Swing, was schon mit dem JRE dabei ist. Allerdings ist das so dramatisch auch wieder nicht in Zeiten schneller DSL-Leitungen, dann wird’s eben nachgeladen.<\/p>\n

Was aber noch dazu kommt: SWT braucht native Libraries und native Libraries lassen sich nicht so einfach \u00fcber den ClassLoader nachladen, wie irgendwelche Java-Klassen.<\/p>\n

Ist das Applet allerdings signiert, dann ist auch das kein Problem und was dann mit relativ wenig Aufwand m\u00f6glich ist …<\/p>\n

<\/p>\n

Das Bespiel zeigt ein SWT Demo von IBM: den FileViewer. Die Klasse ist so gut wie nicht ge\u00e4ndert worden, lediglich die Initialisierung der Shell muss etwas anders aussehen.<\/p>\n

Dann habe ich noch einen kleinen Bootstrap-Loader f\u00fcr SWT geschrieben (bislang nur f\u00fcr Windows) und schon startet ein SWT Applet<\/a>.<\/p>\n

Achtung<\/strong>: Das Applet ist zwar nur ein Demo, aber der FileViewer ist echt: z.B. Doppelklick auf ein Word-Dokument startet Word!!<\/p>\n

Bemerkung: das Applet ist signiert und erh\u00e4lt nach Best\u00e4tigung das Recht SWT zu installieren. Dazu werden zwei DLLs heruntergeladen und auf dem Java-Library-Path gespeichert. Sollte dies auf Grund unzureichender Rechte des angemeldeten Benutzers nicht funktionieren, so startet das Demo nicht korrekt und liefert stattdessen einen Fehler.<\/p>\n

Code:<\/p>\n

package <\/span>com.rinke.solutions;<\/span><\/tt><\/p>\n

import <\/span>java.applet.Applet;
\n<\/span>import <\/span>java.awt.Canvas;
\n<\/span>import <\/span>java.awt.FlowLayout;
\n<\/span>import <\/span>java.io.File;
\n<\/span>import <\/span>java.io.FileOutputStream;
\n<\/span>import <\/span>java.io.IOException;
\n<\/span>import <\/span>java.io.InputStream;
\n<\/span>import <\/span>java.net.MalformedURLException;
\n<\/span>import <\/span>java.net.URL;<\/span><\/p>\n

import <\/span>javax.swing.JOptionPane;<\/span><\/p>\n

import <\/span>org.eclipse.swt.SWT;
\n<\/span>import <\/span>org.eclipse.swt.awt.SWT_AWT;
\n<\/span>import <\/span>org.eclipse.swt.examples.fileviewer.FileViewer;
\n<\/span>import <\/span>org.eclipse.swt.graphics.Point;
\n<\/span>import <\/span>org.eclipse.swt.layout.FillLayout;
\n<\/span>import <\/span>org.eclipse.swt.widgets.Display;
\n<\/span>import <\/span>org.eclipse.swt.widgets.Shell;<\/span><\/p>\n

public class <\/span>SWTApplet <\/span>extends <\/span>Applet <\/span>{<\/span><\/p>\n

@Override
\n<\/span>public <\/span>void <\/span>init<\/span>() {<\/p>\n

<\/span>super<\/span>.init<\/span>()<\/span>;
\n<\/span>try <\/span>{
\n<\/span>Runtime.getRuntime<\/span>()<\/span>.loadLibrary<\/span>(<\/span>“swt-win32-3139.dll”<\/span>)<\/span>;
\n<\/span>} <\/span>catch<\/span>( <\/span>Throwable e<\/span>) {
\n<\/span>System.out.println<\/span>(<\/span>“Load Library failed” <\/span>)<\/span>;
\nString path = System.getProperty<\/span>(<\/span>“java.library.path”<\/span>)<\/span>;
\nString<\/span>[] <\/span>paths = path.split<\/span>(<\/span>File.pathSeparator<\/span>)<\/span>;
\nString targetDir = <\/span>null<\/span>;
\n<\/span>for <\/span>(<\/span>int <\/span>i = <\/span>0<\/span>; i < paths.length; i++<\/span>) {
\n<\/span>String t = paths<\/span>[<\/span>i<\/span>]<\/span>;
\n<\/span>if<\/span>( <\/span>testWriteable<\/span>(<\/span>t<\/span>) ) {
\n<\/span>targetDir = t;
\n<\/span>break<\/span>;
\n<\/span>}
\n}
\n<\/span>if<\/span>( <\/span>targetDir != <\/span>null <\/span>) {
\n<\/span>download<\/span>( <\/span>“swt-win32-3139.dll”<\/span>, targetDir <\/span>)<\/span>;
\ndownload<\/span>( <\/span>“swt-awt-win32-3139.dll”<\/span>, targetDir <\/span>)<\/span>;
\n<\/span>} <\/span>else <\/span>{
\n<\/span>JOptionPane.showMessageDialog<\/span>(<\/span>this,<\/span>“Could not download swt dlls, java.library.path not writeable”<\/span>,
\n<\/span>“Error Downloading DLLs”<\/span>, JOptionPane.ERROR_MESSAGE<\/span>)<\/span>;
\n<\/span>}
\n}<\/p>\n

<\/span>resize<\/span>(<\/span>640<\/span>, <\/span>400<\/span>)<\/span>;
\n<\/span>final <\/span>Canvas c = <\/span>new <\/span>Canvas<\/span>()<\/span>;
\nsetLayout<\/span>(<\/span>new <\/span>FlowLayout<\/span>())<\/span>;
\nc.setSize<\/span>(<\/span>640<\/span>, <\/span>400<\/span>)<\/span>;
\nadd<\/span>(<\/span>c<\/span>)<\/span>;<\/p>\n

<\/span>new <\/span>Thread<\/span>( <\/span>new <\/span>Runnable<\/span>() {<\/span><\/p>\n

public <\/span>void <\/span>run<\/span>() {
\n<\/span>createSWT<\/span>(<\/span>c<\/span>)<\/span>;
\n<\/span>}<\/p>\n

})<\/span>.start<\/span>()<\/span>;<\/span>
\n}<\/p>\n

<\/span>private <\/span>boolean <\/span>testWriteable<\/span>(<\/span>String dir<\/span>) {
\n<\/span>try <\/span>{
\n<\/span>FileOutputStream fos = <\/span>new <\/span>FileOutputStream<\/span>( <\/span>dir + File.pathSeparator + <\/span>“test” <\/span>)<\/span>;
\nfos.write<\/span>(<\/span>1<\/span>)<\/span>;
\nfos.close<\/span>()<\/span>;
\nFile f = <\/span>new <\/span>File<\/span>( <\/span>dir + File.pathSeparator + <\/span>“test” <\/span>)<\/span>;
\nf.delete<\/span>()<\/span>;
\n<\/span>return true<\/span>;
\n<\/span>} <\/span>catch<\/span>( <\/span>Exception e<\/span>){<\/p>\n

}
\n<\/span>return false<\/span>;
\n<\/span>}<\/span><\/p>\n

private <\/span>void <\/span>download<\/span>(<\/span>String filename, String targetDir<\/span>) {
\n<\/span>try <\/span>{
\n<\/span>URL url = <\/span>new <\/span>URL<\/span>( <\/span>getCodeBase<\/span>() <\/span>+ filename <\/span>)<\/span>;
\nInputStream is = url.openStream<\/span>()<\/span>;
\nFile of = <\/span>new <\/span>File<\/span>(<\/span>targetDir + <\/span>“\/” <\/span>+ filename<\/span>)<\/span>;
\nFileOutputStream o = <\/span>new <\/span>FileOutputStream<\/span>( <\/span>of <\/span>)<\/span>;
\nSystem.out.println<\/span>(<\/span>“downloading from ” <\/span>+ url + <\/span>“to ” <\/span>+ of.getAbsolutePath<\/span>())<\/span>;
\n<\/span>byte<\/span>[] <\/span>buffer = <\/span>new <\/span>byte<\/span>[<\/span>10000<\/span>]<\/span>;
\n<\/span>while<\/span>( <\/span>true <\/span>) {
\n<\/span>int <\/span>c = is.read<\/span>(<\/span>buffer<\/span>)<\/span>;
\n<\/span>if<\/span>( <\/span>c == –<\/span>1 <\/span>) <\/span>break<\/span>;
\no.write<\/span>(<\/span>buffer,<\/span>0<\/span>,c<\/span>)<\/span>;
\n<\/span>}
\n<\/span>o.close<\/span>()<\/span>;
\nis.close<\/span>()<\/span>;
\n<\/span>} <\/span>catch <\/span>(<\/span>MalformedURLException e<\/span>) {
\n<\/span>\/\/ TODO Auto-generated catch block
\n<\/span>e.printStackTrace<\/span>()<\/span>;
\n<\/span>} <\/span>catch <\/span>(<\/span>IOException e<\/span>) {
\n<\/span>\/\/ TODO Auto-generated catch block
\n<\/span>e.printStackTrace<\/span>()<\/span>;
\n<\/span>}<\/p>\n

}<\/span><\/p>\n

Shell shell;<\/span><\/p>\n

Display display;<\/p>\n

protected <\/span>void <\/span>createSWT<\/span>(<\/span>Canvas c<\/span>) {
\n<\/span>display = <\/span>new <\/span>Display<\/span>()<\/span>;
\nshell = SWT_AWT.new_Shell<\/span>(<\/span>display, c<\/span>)<\/span>;<\/span><\/p>\n

shell.setLayout(<\/span>new <\/span>FillLayout<\/span>())<\/span>;<\/span><\/p>\n

FileViewer app = new <\/span>FileViewer<\/span>()<\/span>;<\/p>\n

app.open<\/span>(<\/span>display,shell<\/span>)<\/span>;<\/p>\n

<\/span>\/\/ Size AWT Panel so that it is big enough to hold the SWT widgets
\n<\/span>Point size = shell.computeSize <\/span>(<\/span>SWT.DEFAULT, SWT.DEFAULT<\/span>)<\/span>;
\nc.setSize<\/span>(<\/span>size.x + <\/span>2<\/span>, size.y + <\/span>200<\/span>)<\/span>;<\/p>\n

validate<\/span>()<\/span>;<\/span><\/p>\n

\/\/ shell.open();
\n<\/span>while <\/span>(<\/span>!shell.isDisposed<\/span>())
\n<\/span>if <\/span>(<\/span>!display.readAndDispatch<\/span>())
\n<\/span>display.sleep<\/span>()<\/span>;<\/span>
\n}<\/span><\/p>\n

}<\/p><\/blockquote>\n

[:en]<\/p>\n

Recently I asked myself, why swt applications couldn’t run as applet actually? Okay one certain reason is swt is not part of the jre as swing is. However this should not be to dramatic in times of highspeed internet connections, we can download and install it on the fly.\n<\/p>\n

\nBut in addition: SWT needs native libraries and native libraries could not easily loaded by an url classloader like some simple java class files.\n<\/p>\n

\nBut if the applet is signet, then even this isn’t really a problem, and then with little effort you can see …\n<\/p>\n

<\/p>\n

\nThe example demonstrates a swt demo by IBM: the FileViewer. The class isn’t virtually changed, solely the initialiasation of the shell looks somewaht different.\n<\/p>\n

\nFurther on I added a simple boot loader for swt applets (until now its windows only) und yet a SWT Applet<\/a> starts.\n<\/p>\n

\nWarning<\/strong>: This applet indeed is just a demo, but the FileViewer is real: for instance a double click on a word document starts word!!\n<\/p>\n

\nNote: the applet is signet and gets the permission to install swt after confirmation. To achieve this the applet will dowload two DLLs and store them to the java library path. If this isn’t possible due insufficient rights of the user logged in, the demo wont start and you will get an error message.\n<\/p>\n

Code:<\/p>\n

\npackage <\/span>com.rinke.solutions;<\/p>\n

<\/span>import <\/span>java.applet.Applet;
\n<\/span>import <\/span>java.awt.Canvas;
\n<\/span>import <\/span>java.awt.FlowLayout;
\n<\/span>import <\/span>java.io.File;
\n<\/span>import <\/span>java.io.FileOutputStream;
\n<\/span>import <\/span>java.io.IOException;
\n<\/span>import <\/span>java.io.InputStream;
\n<\/span>import <\/span>java.net.MalformedURLException;
\n<\/span>import <\/span>java.net.URL;<\/p>\n

<\/span>import <\/span>javax.swing.JOptionPane;<\/p>\n

<\/span>import <\/span>org.eclipse.swt.SWT;
\n<\/span>import <\/span>org.eclipse.swt.awt.SWT_AWT;
\n<\/span>import <\/span>org.eclipse.swt.examples.fileviewer.FileViewer;
\n<\/span>import <\/span>org.eclipse.swt.graphics.Point;
\n<\/span>import <\/span>org.eclipse.swt.layout.FillLayout;
\n<\/span>import <\/span>org.eclipse.swt.widgets.Display;
\n<\/span>import <\/span>org.eclipse.swt.widgets.Shell;<\/p>\n

<\/span>public class <\/span>SWTApplet <\/span>extends <\/span>Applet <\/span>{<\/p>\n

<\/span>@Override
\n <\/span>public <\/span>void <\/span>init<\/span>() {<\/p>\n

<\/span>super<\/span>.init<\/span>()<\/span>;
\n <\/span>try <\/span>{
\n <\/span>Runtime.getRuntime<\/span>()<\/span>.loadLibrary<\/span>(<\/span>"swt-win32-3139.dll"<\/span>)<\/span>;
\n <\/span>} <\/span>catch<\/span>( <\/span>Throwable e<\/span>) {
\n <\/span>System.out.println<\/span>(<\/span>"Load Library failed" <\/span>)<\/span>;
\n String path = System.getProperty<\/span>(<\/span>"java.library.path"<\/span>)<\/span>;
\n String<\/span>[] <\/span>paths = path.split<\/span>(<\/span>File.pathSeparator<\/span>)<\/span>;
\n String targetDir = <\/span>null<\/span>;
\n <\/span>for <\/span>(<\/span>int <\/span>i = <\/span>0<\/span>; i < paths.length; i++<\/span>) {
\n <\/span>String t = paths<\/span>[<\/span>i<\/span>]<\/span>;
\n <\/span>if<\/span>( <\/span>testWriteable<\/span>(<\/span>t<\/span>) ) {
\n <\/span>targetDir = t;
\n <\/span>break<\/span>;
\n <\/span>}
\n }
\n <\/span>if<\/span>( <\/span>targetDir != <\/span>null <\/span>) {
\n <\/span>download<\/span>( <\/span>"swt-win32-3139.dll"<\/span>, targetDir <\/span>)<\/span>;
\n download<\/span>( <\/span>"swt-awt-win32-3139.dll"<\/span>, targetDir <\/span>)<\/span>;
\n <\/span>} <\/span>else <\/span>{
\n <\/span>JOptionPane.showMessageDialog<\/span>(<\/span>this,<\/span>"Could not download swt dlls, java.library.path not writeable"<\/span>,
\n <\/span>"Error Downloading DLLs"<\/span>, JOptionPane.ERROR_MESSAGE<\/span>)<\/span>;
\n <\/span>}
\n }<\/p>\n

<\/span>resize<\/span>(<\/span>640<\/span>, <\/span>400<\/span>)<\/span>;
\n <\/span>final <\/span>Canvas c = <\/span>new <\/span>Canvas<\/span>()<\/span>;
\n setLayout<\/span>(<\/span>new <\/span>FlowLayout<\/span>())<\/span>;
\n c.setSize<\/span>(<\/span>640<\/span>, <\/span>400<\/span>)<\/span>;
\n add<\/span>(<\/span>c<\/span>)<\/span>;<\/p>\n

<\/span>new <\/span>Thread<\/span>( <\/span>new <\/span>Runnable<\/span>() {<\/p>\n

<\/span>public <\/span>void <\/span>run<\/span>() {
\n <\/span>createSWT<\/span>(<\/span>c<\/span>)<\/span>;
\n <\/span>}<\/p>\n

})<\/span>.start<\/span>()<\/span>;<\/p>\n

\n <\/span>}<\/p>\n

<\/span>private <\/span>boolean <\/span>testWriteable<\/span>(<\/span>String dir<\/span>) {
\n <\/span>try <\/span>{
\n <\/span>FileOutputStream fos = <\/span>new <\/span>FileOutputStream<\/span>( <\/span>dir + File.pathSeparator + <\/span>"test" <\/span>)<\/span>;
\n fos.write<\/span>(<\/span>1<\/span>)<\/span>;
\n fos.close<\/span>()<\/span>;
\n File f = <\/span>new <\/span>File<\/span>( <\/span>dir + File.pathSeparator + <\/span>"test" <\/span>)<\/span>;
\n f.delete<\/span>()<\/span>;
\n <\/span>return true<\/span>;
\n <\/span>} <\/span>catch<\/span>( <\/span>Exception e<\/span>){<\/p>\n

}
\n <\/span>return false<\/span>;
\n <\/span>}<\/p>\n

<\/span>private <\/span>void <\/span>download<\/span>(<\/span>String filename, String targetDir<\/span>) {
\n <\/span>try <\/span>{
\n <\/span>URL url = <\/span>new <\/span>URL<\/span>( <\/span>getCodeBase<\/span>() <\/span>+ filename <\/span>)<\/span>;
\n InputStream is = url.openStream<\/span>()<\/span>;
\n File of = <\/span>new <\/span>File<\/span>(<\/span>targetDir + <\/span>"\/" <\/span>+ filename<\/span>)<\/span>;
\n FileOutputStream o = <\/span>new <\/span>FileOutputStream<\/span>( <\/span>of <\/span>)<\/span>;
\n System.out.println<\/span>(<\/span>"downloading from " <\/span>+ url + <\/span>"to " <\/span>+ of.getAbsolutePath<\/span>())<\/span>;
\n <\/span>byte<\/span>[] <\/span>buffer = <\/span>new <\/span>byte<\/span>[<\/span>10000<\/span>]<\/span>;
\n <\/span>while<\/span>( <\/span>true <\/span>) {
\n <\/span>int <\/span>c = is.read<\/span>(<\/span>buffer<\/span>)<\/span>;
\n <\/span>if<\/span>( <\/span>c == -<\/span>1 <\/span>) <\/span>break<\/span>;
\n o.write<\/span>(<\/span>buffer,<\/span>0<\/span>,c<\/span>)<\/span>;
\n <\/span>}
\n <\/span>o.close<\/span>()<\/span>;
\n is.close<\/span>()<\/span>;
\n <\/span>} <\/span>catch <\/span>(<\/span>MalformedURLException e<\/span>) {
\n <\/span>\/\/ TODO Auto-generated catch block
\n <\/span>e.printStackTrace<\/span>()<\/span>;
\n <\/span>} <\/span>catch <\/span>(<\/span>IOException e<\/span>) {
\n <\/span>\/\/ TODO Auto-generated catch block
\n <\/span>e.printStackTrace<\/span>()<\/span>;
\n <\/span>}<\/p>\n

}<\/p>\n

<\/span>Shell shell;<\/p>\n

Display display;<\/p>\n

<\/span>protected <\/span>void <\/span>createSWT<\/span>(<\/span>Canvas c<\/span>) {
\n <\/span>display = <\/span>new <\/span>Display<\/span>()<\/span>;
\n shell = SWT_AWT.new_Shell<\/span>(<\/span>display, c<\/span>)<\/span>;<\/p>\n

shell.setLayout<\/span>(<\/span>new <\/span>FillLayout<\/span>())<\/span>;<\/p>\n

FileViewer app = <\/span>new <\/span>FileViewer<\/span>()<\/span>;<\/p>\n

app.open<\/span>(<\/span>display,shell<\/span>)<\/span>;<\/p>\n

<\/span>\/\/ Size AWT Panel so that it is big enough to hold the SWT widgets
\n <\/span>Point size = shell.computeSize <\/span>(<\/span>SWT.DEFAULT, SWT.DEFAULT<\/span>)<\/span>;
\n c.setSize<\/span>(<\/span>size.x + <\/span>2<\/span>, size.y + <\/span>200<\/span>)<\/span>;<\/p>\n

validate<\/span>()<\/span>;<\/p>\n

\n <\/span>\/\/ shell.open();
\n <\/span>while <\/span>(<\/span>!shell.isDisposed<\/span>())
\n <\/span>if <\/span>(<\/span>!display.readAndDispatch<\/span>())
\n <\/span>display.sleep<\/span>()<\/span>;<\/p>\n

\n <\/span>}<\/p>\n

}<\/span><\/tt><\/p>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"

[:de]Neulich stellte sich mir die Frage, warum eigentlich nicht auch SWT Applikationen als Applet laufen k\u00f6nnen. Gut der erste Grund ist sicherlich, dass SWT nicht immer installiert ist, im Gegensatz zu Swing, was schon mit dem JRE dabei ist. Allerdings … Weiterlesen →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[],"_links":{"self":[{"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/posts\/15"}],"collection":[{"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/comments?post=15"}],"version-history":[{"count":2,"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/posts\/15\/revisions"}],"predecessor-version":[{"id":55,"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/posts\/15\/revisions\/55"}],"wp:attachment":[{"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/media?parent=15"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/categories?post=15"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cogito-ergo-blog.de\/blog\/wp-json\/wp\/v2\/tags?post=15"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}