jndi study
jndijave naming and directory interface java命名和目录接口。主要用于远程访问对象（标准）。naming service: the means by which names are associated with objects and objects are found based their name, 命名服务，通过名字与对象的联系，我们可以根据名字找到相应的对象
directory service: a directory service associated names with the objects and also allow such objects to have attributes.目录服务，可以说是命名服务的扩展，它不仅联系了对象，并且允许对象拥有属性
java应用程序使用jndi api访问不通的命名和目录服务，jndi提供了访问不同jndi服务标准统一的接口。
几个命名/目录服务的提供者
1 LDAP lightweight directory access protocol com.sun.jndi.ldap.LdapCtxFactory
2 CORBA COSCommon Object request broker architecture Common object services
3 RMI java remote method invocation
4 DNS Domain name system
com.sun.jndi.dns.DnsContextFactory
5 FSSP file system service provider com.sun.jndi.fscontext.RefFSContextFactory
图片中更加可以明白jndi的作用
http://dl.iteye.com/upload/attachment/0068/5576/d5a5e94f-5981-38d4-909d-f6560fffbc75.jpg
java spi server provider interface
Naming operations：
read operations and operations for updating the namespace
Look up an object
List the content of a context
Addind,overwriting,and removing a binding
Renaming an object
Creating and destorying subContexts
Directory operations
Reading a object's attributes
Modifying an object's attributes
Searching a directory
Performing hybrid naming and directory operations
代码，Lookup，通过名字找到找到对象，正如new File("H:/summary.txt");提供名字可以获取File对象。
package ldaptest;import java.io.File;import java.util.Hashtable;import java.util.logging.Level;import java.util.logging.Logger;import javax.naming.Context;import javax.naming.InitialContext;import javax.naming.NamingException;/** * * @author liuquan */public class LdapLookup { public void lookupObject(){ Hashtable ht = new Hashtable(); ht.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.fscontext.RefFSContextFactory"); ht.put(Context.PROVIDER_URL, "file:/H:"); try { Context context = new InitialContext(ht); File file = (File)context.lookup("summary.txt"); System.out.println(file.getAbsolutePath()); } catch (NamingException ex) { Logger.getLogger(LdapLookup.class.getName()).log(Level.SEVERE, null, ex); } } /** * @param args the command line arguments */ public static void main(String[] args) { LdapLookup lookup = new LdapLookup(); lookup.lookupObject(); }}
使用的是file system service。Hashtable存放了二个参数，一个是service的提供者，另一个是访问路径。
代码list the content of the context，得到context内所有内容。如你访问文件夹，那么可以得到这个文件夹里面所有的内容。有二个方法，一个只得到object名字和class名字，另一种还会得到object对象。
package ldaptest;import java.io.File;import java.util.Hashtable;import java.util.logging.Level;import java.util.logging.Logger;import javax.naming.Binding;import javax.naming.Context;import javax.naming.InitialContext;import javax.naming.NameClassPair;import javax.naming.NamingEnumeration;import javax.naming.NamingException;/** * * @author liuquan */public class LdapList { public void listObject() { try { Hashtable ht = new Hashtable(); ht.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.fscontext.RefFSContextFactory"); ht.put(Context.PROVIDER_URL, "file:/H:"); Context context = new InitialContext(ht); NamingEnumeration list = context.list("summary"); while (list.hasMore()) { NameClassPair ncp = (NameClassPair) list.next(); System.out.println(ncp); System.out.println(ncp.getName()); System.out.println(ncp.getClassName()); } } catch (NamingException ex) { Logger.getLogger(LdapList.class.getName()).log(Level.SEVERE, null, ex); } } public void listBindingObject() { try { Hashtable ht = new Hashtable(); ht.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.fscontext.RefFSContextFactory"); ht.put(Context.PROVIDER_URL, "file:/H:"); Context context = new InitialContext(ht); NamingEnumeration list = context.listBindings("summary"); while (list.hasMore()) { Binding b = (Binding) list.next(); System.out.println(b); System.out.println(b.getObject()); File file = (File) b.getObject(); System.out.println(file.getAbsolutePath()); } } catch (NamingException ex) { Logger.getLogger(LdapList.class.getName()).log(Level.SEVERE, null, ex); } } public static void main(String args[]) { LdapList ll = new LdapList(); ll.listObject(); ll.listBindingObject(); }}
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