{"id":1357,"date":"2014-02-14T00:57:34","date_gmt":"2014-02-13T22:57:34","guid":{"rendered":"http:\/\/hasselba.ch\/blog\/?p=1357"},"modified":"2014-02-14T01:01:58","modified_gmt":"2014-02-13T23:01:58","slug":"quick-n-dirty-use-old-school-javacode-in-your-xpages-application","status":"publish","type":"post","link":"https:\/\/hasselba.ch\/blog\/?p=1357","title":{"rendered":"Quick-n-Dirty: Use „Old-School“ Javacode in your XPages-Application"},"content":{"rendered":"

Because I often have read that it is not possible to access „Old School“ Java elements in XPages, but never understood the reason why, I have written my own class loader for fun to demonstrate how to do this:<\/p>\n

1. I have created a simple Java library:<\/p>\n

\"\"<\/p>\n

2. The library contains a single class „LoadedClass<\/em>„:<\/p>\n

\"\"<\/p>\n

The class is very simple. When it is instantiated, it just prompts the current timestamp to the server console:<\/p>\n

package ch.hasselba.test;\r\n\r\npublic class LoadedClass { \r\n\r\n\u00a0\u00a0 \u00a0public LoadedClass(){\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0System.out.println(\"Time: \" + System.currentTimeMillis() );\r\n\u00a0\u00a0 \u00a0}\r\n}\r\n<\/code><\/pre>\n
3. If you inspecting the Java design element, you will notice a attachment with the name %%object.jar%%<\/em>. That’s the compiled library:<\/p>\n
\"\"<\/p>\n
And here is the UNID of the design element for accessing it<\/p>\n
\"\"<\/p>\n
4. Now it is time for the class loader (the modified code originally came from Laurentiu Cristofor):<\/p>\n
package ch.hasselba.demo;\r\n\r\nimport java.io.ByteArrayInputStream;\r\nimport java.io.ByteArrayOutputStream;\r\nimport java.io.IOException;\r\nimport java.util.Hashtable;\r\nimport java.util.jar.JarEntry;\r\nimport java.util.jar.JarInputStream;\r\n\r\n\/**\r\n\u00a0* \r\n\u00a0* This class implements a simple class loader that can be used to load at\r\n\u00a0* runtime classes contained in a JAR file.\r\n\u00a0* \r\n\u00a0* (P)2000 Laurentiu Cristofor\r\n\u00a0* \r\n\u00a0* Modified 2014 by Sven Hasselbach\r\n\u00a0* \r\n\u00a0*\/\r\npublic class JarClassLoader extends ClassLoader {\r\n\u00a0\u00a0 \u00a0private Hashtable jarContents;\r\n\r\n\u00a0\u00a0 \u00a0\/**\r\n\u00a0\u00a0 \u00a0 * Creates a new JarClassLoader that will allow the loading of classes\r\n\u00a0\u00a0 \u00a0 * stored in a jar file.\r\n\u00a0\u00a0 \u00a0 * \r\n\u00a0\u00a0 \u00a0 * @param bos\r\n\u00a0\u00a0 \u00a0 *\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 ByteArrayOutputStream containing a Jar\r\n\u00a0\u00a0 \u00a0 * @exception IOException\r\n\u00a0\u00a0 \u00a0 *\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 an error happened while reading the contents of the jar\r\n\u00a0\u00a0 \u00a0 *\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 file\r\n\u00a0\u00a0 \u00a0 *\/\r\n\u00a0\u00a0 \u00a0public JarClassLoader(ByteArrayOutputStream bos) throws IOException {\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ second get contents of the jar file and place each\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ entry in a hashtable for later use\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0jarContents = new Hashtable();\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0JarInputStream jis = new JarInputStream(new ByteArrayInputStream(bos\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0.toByteArray()));\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0JarEntry je;\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0while ((je = jis.getNextJarEntry()) != null) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ make sure we have only slashes, we prefer unix, not windows\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0String name = je.getName().replace('\\\\', '\/');\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ get entry size from the entry or from our hashtable\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0int size = bos.size();\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ read the entry\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0byte[] ba = new byte[size];\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0int bytes_read = 0;\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0while (bytes_read != size) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0int r = jis.read(ba, bytes_read, size - bytes_read);\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0if (r < 0)\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0break;\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0bytes_read += r;\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0}\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0jarContents.put(name, ba);\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0}\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0jis.close();\r\n\u00a0\u00a0 \u00a0}\r\n\r\n\u00a0\u00a0 \u00a0\/**\r\n\u00a0\u00a0 \u00a0 * Looks among the contents of the jar file (cached in memory) and tries to\r\n\u00a0\u00a0 \u00a0 * find and define a class, given its name.\r\n\u00a0\u00a0 \u00a0 * \r\n\u00a0\u00a0 \u00a0 * @param className\r\n\u00a0\u00a0 \u00a0 *\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 the name of the class\r\n\u00a0\u00a0 \u00a0 * @return a Class object representing our class\r\n\u00a0\u00a0 \u00a0 * @exception ClassNotFoundException\r\n\u00a0\u00a0 \u00a0 *\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 the jar file did not contain a class named\r\n\u00a0\u00a0 \u00a0 *\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <code>className<\/code>\r\n\u00a0\u00a0 \u00a0 *\/\r\n\u00a0\u00a0 \u00a0public Class findClass(String className) throws ClassNotFoundException {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ transform the name to a path\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0String classPath = className.replace('.', '\/') + \".class\";\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0byte[] classBytes = (byte[]) jarContents.get(classPath);\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0if (classBytes == null)\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0throw new ClassNotFoundException();\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0return defineClass(className, classBytes, 0, classBytes.length);\r\n\u00a0\u00a0 \u00a0}\r\n}\r\n<\/code><\/pre>\n
The trick is to ignore the size of the JarEntries and use the size of the whole ByteArrayOutputStream.<\/p>\n
5. Now we need to load the design element, extract the Jar and load our test class:<\/p>\n
package ch.hasselba.demo;\r\n\r\nimport ch.hasselba.demo.JarClassLoader;\r\n\r\nimport java.io.ByteArrayOutputStream;\r\nimport java.io.FileInputStream;\r\nimport lotus.domino.Database;\r\nimport lotus.domino.Document;\r\nimport lotus.domino.EmbeddedObject;\r\nimport lotus.domino.Session;\r\n\r\npublic class JavaLoader {\r\n\r\n\u00a0\u00a0 \u00a0public JavaLoader(Session session) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0try {\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0Database db = session.getCurrentDatabase();\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ get the design document\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0Document doc = db\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0.getDocumentByUNID(\"6783F550459C81B1C1257C7E007A5D44\");\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ get the attachment\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0EmbeddedObject embObj = doc.getAttachment(\"%%object%%.jar\");\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0FileInputStream fis = (FileInputStream) embObj.getInputStream();\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ convert the FileInputStream to a ByteArrayOutputStream\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0ByteArrayOutputStream bos = new ByteArrayOutputStream();\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0int data;\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0while ((data = fis.read()) != (-1)) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0bos.write(data);\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0}\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0bos.flush();\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ load the Jar with the class loader\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0JarClassLoader jcl = new JarClassLoader(bos);\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ get the class\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0Class loadedClass = jcl.findClass(\"ch.hasselba.test.LoadedClass\");\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\/\/ and instantiate it\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0Object obj = loadedClass.newInstance();\r\n\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0} catch (Exception e) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0e.printStackTrace();\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0}\r\n\u00a0\u00a0 \u00a0}\r\n}<\/code><\/pre>\n
6. Last but not least, a XPage for demonstrating how to use the code:<\/p>\n
<?xml version=\"1.0\" encoding=\"UTF-8\"?>\r\n<xp:view xmlns:xp=\"http:\/\/www.ibm.com\/xsp\/core\">\r\n\r\n\u00a0\u00a0 \u00a0<xp:button value=\"Label\" id=\"button1\">\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0<xp:eventHandler event=\"onclick\" submit=\"true\" refreshMode=\"complete\">\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0<xp:this.action>\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0<![CDATA[#{javascript:\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0importPackage( ch.hasselba.demo );\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0new ch.hasselba.demo.JavaLoader(session);}]]>\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0<\/xp:this.action>\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0<\/xp:eventHandler>\r\n\u00a0\u00a0 \u00a0<\/xp:button>\r\n\r\n<\/xp:view><\/code><\/pre>\n
7. If you open the XPage and click the button…<\/p>\n
\"\"<\/p>\n
… you can see the result on the server console:<\/p>\n
\"\"<\/p>\n
If you want to access the methods and\/or properties of the loaded object, you have do do this with reflection.<\/p>\n
P.S.\u00a0Keep in mind that this article has been posted in the \u201cQuick-n-Dirty<\/strong>\u201d category.<\/p>\n","protected":false},"excerpt":{"rendered":"
Because I often have read that it is not possible to access „Old School“ Java elements in XPages, but never understood the reason why, I have written my own class loader for fun to demonstrate how to do this: 1. … 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":[89,74],"tags":[47,7,31,3],"class_list":["post-1357","post","type-post","status-publish","format-standard","hentry","category-java","category-xpages","tag-9-0","tag-domino","tag-java","tag-xpages"],"_links":{"self":[{"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1357","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1357"}],"version-history":[{"count":5,"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1357\/revisions"}],"predecessor-version":[{"id":1362,"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1357\/revisions\/1362"}],"wp:attachment":[{"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1357"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1357"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hasselba.ch\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1357"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}