クラス org.objectweb.cjdbc.controller.connection.DriverClassLoader

すべてのメンバ一覧

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説明

This class defines a DriverClassLoader used to load drivers with their own classloder to be able to handle different implementations of drivers sharing the same class name. For example if you want to connect to two backends of the same vendor, but running with different releases and requiring a driver compatible with the respective database release

作者:

Emmanuel Cecchet

バージョン:

1.0

DriverClassLoader.java の 57 行で定義されています。

Protected メソッド
Class	findClass (String className) throws ClassNotFoundException
URL	findResource (String name)
関数
	DriverClassLoader (ClassLoader parent, File pPath)
Private メソッド
byte[]	findClassInJarFile (File dir, String className) throws IOException
String	convertClassNameToResourceName (String className)
void	loadJarFile (String jarFileName) throws IOException
Private 変数
File	path = null
Hashtable	htJarContents = new Hashtable()

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コンストラクタとデストラクタ

org.objectweb.cjdbc.controller.connection.DriverClassLoader.DriverClassLoader (  ClassLoader  parent, File  pPath )  [package]

Creates a new DriverClassLoader.java object 引数: parent  classloader, null if no parent classloader should be used pPath  path where the driver classfiles of jar files are located DriverClassLoader.java の 69 行で定義されています。 参照先 org.objectweb.cjdbc.controller.connection.DriverClassLoader.path. { super(parent); path = pPath; if (path == null) path = new File(""); }

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メソッド

String org.objectweb.cjdbc.controller.connection.DriverClassLoader.convertClassNameToResourceName (  String  className  )  [private]

convert the class name into the rescource name. This method is just replacing the '.' in the name with a '/' and adding the suffix '.class' 引数: className  戻り値: resource name DriverClassLoader.java の 280 行で定義されています。 参照元 org.objectweb.cjdbc.controller.connection.DriverClassLoader.findClassInJarFile(). { String resourceName = className; resourceName = resourceName.replace('.', '/'); resourceName = resourceName + ".class"; return resourceName; }

Class org.objectweb.cjdbc.controller.connection.DriverClassLoader.findClass (  String  className  )  throws ClassNotFoundException [protected]

finds the specified class 参照: java.lang.ClassLoader#findClass(java.lang.String) DriverClassLoader.java の 83 行で定義されています。 参照先 org.objectweb.cjdbc.controller.connection.DriverClassLoader.findClassInJarFile(), と org.objectweb.cjdbc.controller.connection.DriverClassLoader.path. { FileInputStream fis = null; try { byte[] classBytes = null; // first we try to locate a class file. String pathName = className.replace('.', File.separatorChar); File file = new File(path.getAbsolutePath(), pathName + ".class"); if (file.exists()) { // we have found a class file and read it fis = new FileInputStream(file); classBytes = new byte[fis.available()]; fis.read(classBytes); } else { // no class file exists we have to check jar files classBytes = findClassInJarFile(path, className); } // we convert the bytes into the specified class Class clazz = defineClass(null, classBytes, 0, classBytes.length); return clazz; } catch (Exception e) { // We could not find the class, so indicate the problem with an exception throw new ClassNotFoundException(className, e); } finally { if (null != fis) { try { fis.close(); } catch (Exception e) { } } } }

byte [] org.objectweb.cjdbc.controller.connection.DriverClassLoader.findClassInJarFile (  File  dir, String  className )  throws IOException [private]

Find the first jar file containing the className and load it 引数: dir  directory where we are looking for jar files className  name of the class we are looking for 戻り値: the class as byte[] 例外: IOException  if an error occurs DriverClassLoader.java の 146 行で定義されています。 参照先 org.objectweb.cjdbc.controller.connection.DriverClassLoader.convertClassNameToResourceName(), org.objectweb.cjdbc.controller.connection.DriverClassLoader.htJarContents, と org.objectweb.cjdbc.controller.connection.DriverClassLoader.loadJarFile(). 参照元 org.objectweb.cjdbc.controller.connection.DriverClassLoader.findClass(). { // is the class already cached ? String resourceName = convertClassNameToResourceName(className); byte[] classBytes = (byte[]) htJarContents.get(resourceName); if (classBytes != null) { // it has been cached, we return return classBytes; } if (!dir.canRead()) throw new IOException(dir + " is not readable."); if (dir.isFile()) { // driverPath specified a jar file loadJarFile(dir.getAbsolutePath()); // after loading the jar file the class bytes are in the cache return (byte[]) htJarContents.get(resourceName); } // the class is not yet cached we have to find the right jar file // find all jar files in the directory String[] jarFiles = dir.list(new FilenameFilter() { public boolean accept(File dir, String name) { return name.endsWith(".jar"); } }); if (jarFiles == null) throw new IOException("Invalid path " + dir); // loop over jar files for (int i = 0; i < jarFiles.length; i++) { File file = new File(dir, jarFiles[i]); JarFile jarFile = new JarFile(file); // we see whether the jar file contains the class we are looking for // no need in loading jar files as long as we don't really need the // content. if (jarFile.getEntry(resourceName) != null) { // we have found the right jar file and are loading it now loadJarFile(jarFile.getName()); // after loading the jar file the class bytes are in the cache classBytes = (byte[]) htJarContents.get(resourceName); } } return classBytes; }

URL org.objectweb.cjdbc.controller.connection.DriverClassLoader.findResource (  String  name  )  [protected]

参照: java.lang.ClassLoader#findResource(java.lang.String) DriverClassLoader.java の 207 行で定義されています。 { // we try to locate the resource unjarred if (path.isDirectory()) { File searchResource = new File(path, name); if (searchResource.exists()) { try { return searchResource.toURL(); } catch (MalformedURLException mfe) { } } } else if (path.isFile()) { // try getting the resource from the file try { new JarFile(path); // convert the jar entry into URL format return new URL("jar:" + path.toURL() + "!/" + name); } catch (Exception e) { // we couldn't find resource in file return null; } } //now we are checking the jar files try { // find all jar files in the directory String[] jarFiles = path.list(new FilenameFilter() { public boolean accept(File dir, String name) { return name.endsWith(".jar"); } }); // loop over jar files for (int i = 0; i < jarFiles.length; i++) { File file = new File(path, jarFiles[i]); JarFile jarFile = new JarFile(file); // we see whether the jar file contains the resource we are looking for if (jarFile.getJarEntry(name) != null) { // convert the jar entry into URL format return new URL("jar:" + file.toURL() + "!/" + name); } } } catch (Exception e) { e.printStackTrace(); } return null; }

void org.objectweb.cjdbc.controller.connection.DriverClassLoader.loadJarFile (  String  jarFileName  )  throws IOException [private]

Load the contents of jar file in the cache 引数: jarFileName  name of the jar file we want to load 例外: IOException  DriverClassLoader.java の 294 行で定義されています。 参照元 org.objectweb.cjdbc.controller.connection.DriverClassLoader.findClassInJarFile(). { Hashtable htSizes = new Hashtable(); // extracts just sizes only. // For a reason I dont' understand not all files return the size in the loop // below (using ZipInputStream). So we cache the sizes here in case the loop // below does not give us the file size ZipFile zf = new ZipFile(jarFileName); Enumeration e = zf.entries(); while (e.hasMoreElements()) { ZipEntry ze = (ZipEntry) e.nextElement(); htSizes.put(ze.getName(), new Integer((int) ze.getSize())); } zf.close(); // extract resources and put them into the hashtable. FileInputStream fis = new FileInputStream(jarFileName); BufferedInputStream bis = new BufferedInputStream(fis); ZipInputStream zis = new ZipInputStream(bis); ZipEntry ze = null; while ((ze = zis.getNextEntry()) != null) { if (ze.isDirectory()) { continue; } int size = (int) ze.getSize(); // -1 means unknown size. if (size == -1) { // that is the reason we have cached the file size above. size = ((Integer) htSizes.get(ze.getName())).intValue(); } byte[] b = new byte[size]; int rb = 0; int chunk = 0; while ((size - rb) > 0) { chunk = zis.read(b, rb, size - rb); if (chunk == -1) { break; } rb += chunk; } // add to internal resource hashtable htJarContents.put(ze.getName(), b); } }

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変数

Hashtable org.objectweb.cjdbc.controller.connection.DriverClassLoader.htJarContents = new Hashtable() [private]

we cache the contents of the jar files, as we don't want to have to read the file for every single class we are going to need DriverClassLoader.java の 136 行で定義されています。 参照元 org.objectweb.cjdbc.controller.connection.DriverClassLoader.findClassInJarFile().

File org.objectweb.cjdbc.controller.connection.DriverClassLoader.path = null [private]

path on filesystem where the driver is located DriverClassLoader.java の 61 行で定義されています。 参照元 org.objectweb.cjdbc.controller.connection.DriverClassLoader.DriverClassLoader(), と org.objectweb.cjdbc.controller.connection.DriverClassLoader.findClass().

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このクラスの説明は次のファイルから生成されました:

• src/org/objectweb/cjdbc/controller/connection/DriverClassLoader.java

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