Java 2 SDK v1.4.2, Java 2 SDK 英文文档

Appendix A: Service Provider Example

This appendix contains a simple service provider. It implements a flat namespace (with no federation support). It shows how to produce a context implementation by providing all the methods in the Context interface.

An instance of this context is bound directly as the initial context. This example provides the corresponding InitialContextFactory definition.

A.1 Simple Flat Context

A.1.1 Context Implementation

/* 
 * @(#)FlatCtx.java	1.3 99/07/26
 * 
 * Copyright 1997, 1998, 1999 Sun Microsystems, Inc. All Rights
 * Reserved.
 * 
 * Sun grants you ("Licensee") a non-exclusive, royalty free,
 * license to use, modify and redistribute this software in source and
 * binary code form, provided that i) this copyright notice and license
 * appear on all copies of the software; and ii) Licensee does not 
 * utilize the software in a manner which is disparaging to Sun.
 *
 * This software is provided "AS IS," without a warranty of any
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE 
 * HEREBY EXCLUDED.  SUN AND ITS LICENSORS SHALL NOT BE LIABLE 
 * FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, 
 * MODIFYING OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN 
 * NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST 
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
 * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER 
 * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT 
 * OF THE USE OF OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS 
 * BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 * 
 * This software is not designed or intended for use in on-line
 * control of aircraft, air traffic, aircraft navigation or aircraft
 * communications; or in the design, construction, operation or
 * maintenance of any nuclear facility. Licensee represents and warrants
 * that it will not use or redistribute the Software for such purposes.  
 */
package examples.spi.flat;

import javax.naming.*;
import java.util.*;

/**
 * A sample service provider that implements a flat namespace in memory.
 */

class FlatCtx implements Context {
    Hashtable myEnv;
    private Hashtable bindings = new Hashtable(11);
    static NameParser myParser = new FlatNameParser();

    FlatCtx(Hashtable environment) {
        myEnv = (environment != null)
	    ? (Hashtable)(environment.clone()) 
	    : null;
    }

    public Object lookup(String name) throws NamingException {
        if (name.equals("")) {
            // Asking to look up this context itself.  Create and return
            // a new instance with its own independent environment.
            return (new FlatCtx(myEnv));
        }
        Object answer = bindings.get(name);
        if (answer == null) {
            throw new NameNotFoundException(name + " not found");
        }
        return answer;
    }

    public Object lookup(Name name) throws NamingException {
        // Flat namespace; no federation; just call string version
        return lookup(name.toString()); 
    }

    public void bind(String name, Object obj) throws NamingException {
        if (name.equals("")) {
            throw new InvalidNameException("Cannot bind empty name");
        }
        if (bindings.get(name) != null) {
            throw new NameAlreadyBoundException(
                    "Use rebind to override");
        }
        bindings.put(name, obj);
    }

    public void bind(Name name, Object obj) throws NamingException {
        // Flat namespace; no federation; just call string version
        bind(name.toString(), obj);
    }

    public void rebind(String name, Object obj) throws NamingException {
        if (name.equals("")) {
            throw new InvalidNameException("Cannot bind empty name");
        }
        bindings.put(name, obj);
    }

    public void rebind(Name name, Object obj) throws NamingException {
        // Flat namespace; no federation; just call string version
        rebind(name.toString(), obj);
    }

    public void unbind(String name) throws NamingException {
        if (name.equals("")) {
            throw new InvalidNameException("Cannot unbind empty name");
        }
        bindings.remove(name);
    }

    public void unbind(Name name) throws NamingException {
        // Flat namespace; no federation; just call string version
        unbind(name.toString());
    }

    public void rename(String oldname, String newname)
            throws NamingException {
        if (oldname.equals("") || newname.equals("")) {
            throw new InvalidNameException("Cannot rename empty name");
        }

        // Check if new name exists
        if (bindings.get(newname) != null) {
            throw new NameAlreadyBoundException(newname +
                                                " is already bound");
        }

        // Check if old name is bound
        Object oldBinding = bindings.remove(oldname);
        if (oldBinding == null) {
            throw new NameNotFoundException(oldname + " not bound");
        }

        bindings.put(newname, oldBinding);
    }

    public void rename(Name oldname, Name newname)
            throws NamingException {
        // Flat namespace; no federation; just call string version
        rename(oldname.toString(), newname.toString());
    }

    public NamingEnumeration list(String name)
            throws NamingException {
        if (name.equals("")) {
            // listing this context
            return new FlatNames(bindings.keys());
        } 

        // Perhaps `name' names a context
        Object target = lookup(name);
        if (target instanceof Context) {
            return ((Context)target).list("");
        }
        throw new NotContextException(name + " cannot be listed");
    }

    public NamingEnumeration list(Name name)
            throws NamingException {
        // Flat namespace; no federation; just call string version
        return list(name.toString());
    }

    public NamingEnumeration listBindings(String name)
            throws NamingException {
        if (name.equals("")) {
            // listing this context
            return new FlatBindings(bindings.keys());
        } 

        // Perhaps `name' names a context
        Object target = lookup(name);
        if (target instanceof Context) {
            return ((Context)target).listBindings("");
        }
        throw new NotContextException(name + " cannot be listed");
    }

    public NamingEnumeration listBindings(Name name)
            throws NamingException {
        // Flat namespace; no federation; just call string version
        return listBindings(name.toString());
    }

    public void destroySubcontext(String name) throws NamingException {
        throw new OperationNotSupportedException(
                "FlatCtx does not support subcontexts");
    }

    public void destroySubcontext(Name name) throws NamingException {
        // Flat namespace; no federation; just call string version
        destroySubcontext(name.toString());
    }

    public Context createSubcontext(String name)
            throws NamingException {
        throw new OperationNotSupportedException(
                "FlatCtx does not support subcontexts");
    }

    public Context createSubcontext(Name name) throws NamingException {
        // Flat namespace; no federation; just call string version
        return createSubcontext(name.toString());
    }

    public Object lookupLink(String name) throws NamingException {
        // This flat context does not treat links specially
        return lookup(name);
    }

    public Object lookupLink(Name name) throws NamingException {
        // Flat namespace; no federation; just call string version
        return lookupLink(name.toString());
    }

    public NameParser getNameParser(String name)
            throws NamingException {
        return myParser;
    }

    public NameParser getNameParser(Name name) throws NamingException {
        // Flat namespace; no federation; just call string version
        return getNameParser(name.toString());
    }

    public String composeName(String name, String prefix)
            throws NamingException {
        Name result = composeName(new CompositeName(name),
                                  new CompositeName(prefix));
        return result.toString();
    }

    public Name composeName(Name name, Name prefix)
            throws NamingException {
        Name result = (Name)(prefix.clone());
        result.addAll(name);
        return result;
    }

    public Object addToEnvironment(String propName, Object propVal)
            throws NamingException {
        if (myEnv == null) {
            myEnv = new Hashtable(5, 0.75f);
	} 
	return myEnv.put(propName, propVal);
    }

    public Object removeFromEnvironment(String propName) 
            throws NamingException {
        if (myEnv == null)
            return null;

	return myEnv.remove(propName);
    }

    public Hashtable getEnvironment() throws NamingException {
	if (myEnv == null) {
	    // Must return non-null
	    return new Hashtable(3, 0.75f);
	} else {
            return (Hashtable)myEnv.clone();
	}
    }

    public String getNameInNamespace() throws NamingException {
	return ""; 
    }

    public void close() throws NamingException {
	myEnv = null;
	bindings = null;
    }

    // Class for enumerating name/class pairs
    class FlatNames implements NamingEnumeration {
        Enumeration names;

        FlatNames (Enumeration names) {
            this.names = names;
        }

        public boolean hasMoreElements() {
            return names.hasMoreElements();
        }

        public boolean hasMore() throws NamingException {
            return hasMoreElements();
        }

        public Object nextElement() {
            String name = (String)names.nextElement();
            String className = bindings.get(name).getClass().getName();
            return new NameClassPair(name, className);
        }

        public Object next() throws NamingException {
            return nextElement();
        }
	public void close() {
	}
    }

    // Class for enumerating bindings
    class FlatBindings implements NamingEnumeration {
        Enumeration names;

        FlatBindings (Enumeration names) {
            this.names = names;
        }

        public boolean hasMoreElements() {
            return names.hasMoreElements();
        }

        public boolean hasMore() throws NamingException {
            return hasMoreElements();
        }

        public Object nextElement() {
            String name = (String)names.nextElement();
            return new Binding(name, bindings.get(name));
        }

        public Object next() throws NamingException {
            return nextElement();
        }
	public void close() {
	}
    }
};

A.1.2 Name Parser

/*
 * @(#)FlatNameParser.java	1.3 99/07/26
 *
 * Copyright 1997, 1998, 1999 Sun Microsystems, Inc. All Rights
 * Reserved.
 *
 * Sun grants you ("Licensee") a non-exclusive, royalty free,
 * license to use, modify and redistribute this software in source and
 * binary code form, provided that i) this copyright notice and license
 * appear on all copies of the software; and ii) Licensee does not 
 * utilize the software in a manner which is disparaging to Sun.
 *
 * This software is provided "AS IS," without a warranty of any
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE 
 * HEREBY EXCLUDED.  SUN AND ITS LICENSORS SHALL NOT BE LIABLE 
 * FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, 
 * MODIFYING OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN 
 * NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST 
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
 * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER 
 * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT 
 * OF THE USE OF OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS 
 * BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * This software is not designed or intended for use in on-line
 * control of aircraft, air traffic, aircraft navigation or aircraft
 * communications; or in the design, construction, operation or
 * maintenance of any nuclear facility. Licensee represents and warrants
 * that it will not use or redistribute the Software for such purposes. 
 */
package examples.spi.flat;

import javax.naming.NameParser;
import javax.naming.Name;
import javax.naming.CompoundName;
import javax.naming.NamingException;
import java.util.Properties;

class FlatNameParser implements NameParser {

    static Properties syntax = new Properties();
    static {
        syntax.put("jndi.syntax.direction", "flat");
        syntax.put("jndi.syntax.ignorecase", "false");
    }
    public Name parse(String name) throws NamingException {
        return new CompoundName(name, syntax);
    }
}

A.1.3 Initial Context Factory

/*
 * @(#)FlatInitCtxFactory.java	1.3 99/07/26
 *
 * Copyright 1997, 1998, 1999 Sun Microsystems, Inc. All Rights
 * Reserved.
 *
 * Sun grants you ("Licensee") a non-exclusive, royalty free,
 * license to use, modify and redistribute this software in source and
 * binary code form, provided that i) this copyright notice and license
 * appear on all copies of the software; and ii) Licensee does not 
 * utilize the software in a manner which is disparaging to Sun.
 *
 * This software is provided "AS IS," without a warranty of any
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE 
 * HEREBY EXCLUDED.  SUN AND ITS LICENSORS SHALL NOT BE LIABLE 
 * FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, 
 * MODIFYING OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN 
 * NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST 
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
 * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER 
 * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT 
 * OF THE USE OF OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS 
 * BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * This software is not designed or intended for use in on-line
 * control of aircraft, air traffic, aircraft navigation or aircraft
 * communications; or in the design, construction, operation or
 * maintenance of any nuclear facility. Licensee represents and warrants
 * that it will not use or redistribute the Software for such purposes. 
 */
package examples.spi.flat;

import java.util.Hashtable;
import javax.naming.Context;
import javax.naming.spi.InitialContextFactory;

public class FlatInitCtxFactory implements InitialContextFactory {

    public Context getInitialContext(Hashtable env) {
        return new FlatCtx(env);
    }
}

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