basenaming.java

Tomcat 4.1与WebServer集成组件的源代码包.

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package org.apache.naming.core;

import java.util.*;
import javax.naming.*;
import javax.naming.directory.DirContext;
import javax.naming.directory.Attributes;
import javax.naming.directory.Attribute;
import javax.naming.directory.ModificationItem;
import javax.naming.directory.SearchControls;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.util.IntrospectionUtils;

// Based on a merge of various catalina naming contexts
// Name is used - it provide better oportunities for reuse and optimizations

/**
 *  This is the base class for our naming operations, for easy reading.
 *
 *  <p>Creating a new context:
 *  <ul>
 *  <li>Create a new class, extending BaseContext or BaseDirContext ( second
 *      if you want to support attributes ).
 *  <li>Add setters for configuration. The setters will be called autmatically,
 *      like in ant, from the initial env settings.
 *  <li>Override methods that are defined in BaseNaming. Default behavior
 *      is provided for all.
 *  <li>If performance is a concern or have special behavior - override Context and
 *      DirContext methods. That shouldn't be needed in most cases.
 *  </ul>
 *
 *  This class is designed to minimize the ammount of code that is required to
 * create a new context. The usual DirContext interface has way too many methods,
 *  so implementation requires a lot of typing.
 *
 *  Our contexts are mostly wrappers for files or in memory structures. That means
 *  some operations are cheaper, and we're far from the features that would be
 *  exposed for an LDAP or real Directory server.
 *
 * @author Remy Maucherat
 * @author Costin Manolache
 */
public class BaseNaming {

    /**
     * Builds a base directory context.
     */
    public BaseNaming() {
        this.env=new Hashtable();
    }

    /**
     * Builds a base directory context using the given environment.
     */
    public BaseNaming(Hashtable env) {
        this.env=new Hashtable();
        if (env != null ) {
            Enumeration envEntries = env.keys();
            while (envEntries.hasMoreElements()) {
                String entryName = (String) envEntries.nextElement();
                Object entryValue=env.get(entryName);
                this.env.put(entryName, entryValue);
                try {
                    // XXX We need a mechanism to select properties for
                    // this task. Maybe all contexts should use as property prefix the
                    // class name ? Or base class name ? 
                    IntrospectionUtils.setAttribute( this, entryName, entryValue );
                } catch(Exception ex ) {
                    System.out.println("Unsuported property " + entryName + " " + ex.getMessage());
                }
            }
        }
    }

    // ----------------------------------------------------- Instance Variables

    /**
     * Environment. All context config info.
     */
    protected Hashtable env;

    /**
     * Default name parser for this context.
     * XXX This should be combined with the Tomcat mapper, and
     * optimized for MessageBytes.
     */
    protected final NameParser nameParser = new NameParserImpl();

    /**
     * Cached.
     * deprecated ? Should be implemented via notes or other mechanism.
     * Or via config.
     */
    protected boolean cached = true;
    protected int cacheTTL = 5000; // 5s
    protected int cacheObjectMaxSize = 32768; // 32 KB

    
    /** Prefix used for URL-based namming lookup. It must be removed
     *  from all names.
     *  Deprecated ? Do we need it ?
     */
    protected String urlPrefix="";

    // ------------------------------------------------------------- Properties
    // Common properties, apply to all jtc naming contexts.
    
    // XXX Introspection should be used to turn the Hashtable attributes
    // into setters.
    public void setURLPrefix( String s ) {
        urlPrefix=s;
    }
    
    /**
     * Set cached attribute. If false, this context will be skipped from caching
     */
    public void setCached(boolean cached) {
        this.cached = cached;
    }

    /**
     * Is cached ?
     */
    public boolean isCached() {
        return cached;
    }
    public boolean getCached() {
        return cached;
    }


    /**
     * Set cache TTL.
     */
    public void setCacheTTL(int cacheTTL) {
        this.cacheTTL = cacheTTL;
    }


    /**
     * Get cache TTL.
     */
    public int getCacheTTL() {
        return cacheTTL;
    }


    /**
     * Set cacheObjectMaxSize.
     */
    public void setCacheObjectMaxSize(int cacheObjectMaxSize) {
        this.cacheObjectMaxSize = cacheObjectMaxSize;
    }


    /**
     * Get cacheObjectMaxSize.
     */
    public int getCacheObjectMaxSize() {
        return cacheObjectMaxSize;
    }

    // -------------------- Lifecycle methods ? -------------------- 

    /**
     * Allocate resources for this directory context.
     */
    public void allocate() {
        ; // No action taken by the default implementation
    }


    /**
     * Release any resources allocated for this directory context.
     */
    public void release() {
        ; // No action taken by the default implementation
    }

    public void recycle() {
        // nothing yet.
    }
    
    // -------------------- Not so Abstract methods -------------------- 
    // This is what a subclass should implement.

    // XXX Base resolveLinks() method ?? And then use lookup without resolveLinks flag
    
    /** The lookup method. This is the main method you should implement.
     *
     * @param Name
     * @param resolveLinks. If false, this is a lookupLink call. 
     */
    public Object lookup(Name name, boolean resolveLinks)
        throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    /** The setter method. Implement it if the context is read/write.
     *
     * @param name 
     * @param obj The object to be bound.
     * @param attrs Attributes - if this is a dir context, null otherwise
     * @param rebind What to do if the name is already bound. 
     *     XXX can be further simplified - do a lookup and implement it. 
     */
    public void bind(Name name, Object obj, Attributes attrs, boolean rebind )
        throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    /** Remove a binding. XXX do we need the isContext case ?
     */
    public void unbind(Name name, boolean isContext)
        throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    /* XXX There are 2 ways to list the childs: array ( size/elementAt ) or
       iterator/Enumeration. Since the JNDI interface uses iteration -
       that's what we should use.
       */

    /** Return the child elements, if any.
     *
     * This is a String or Name or Binding or NameClassPari enumeration -
     *  the Context implementation will wrap it as a NamingEnumeration and
     *  construct the right information.
     *
     * XXX name is all we need - all other info can be extracted - with some
     * penalty. It's easy to do some instanceof tricks to avoid it, if possible,
     * but the goal is to make it easy to write contexts, and name should be
     * enough.
     */
    public Enumeration getChildren() throws NamingException {
        return null;
    }

    public DirContext createSubcontext(Name name, Attributes attrs)
        throws NamingException
    {
        // XXX We can implement a decent default using bind and the current class.
        throw new OperationNotSupportedException();
    }

    public void rename(Name oldName, Name newName)
        throws NamingException
    {
        // Override if needed
        Object value = lookup(oldName, false);
        bind(newName, value, null, false);
        unbind(oldName, true);
        
    }

    /** Implement for directories
     *
     */
    public Object getAttribute( Name name, String attName )
        throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public void setAttribute( Name name, String attName, Object value )
        throws NamingException
    {
        throw new OperationNotSupportedException();
    }

    public String[] getAttributeNames(Name name )
        throws NamingException
    {
        throw new OperationNotSupportedException();
    }


    // -------------------- Utils --------------------
    

    /**
     * Returns true if writing is allowed on this context.
     */
    protected boolean isWritable(Name name) {
        return ContextAccessController.isWritable(name);
    }


    /**
     * Throws a naming exception is Context is not writable.
     */
    protected void checkWritable(Name n) 
        throws NamingException
    {
        if (!isWritable(n))
            throw new NamingException("read only");
    }

    protected Name string2Name(String s ) throws InvalidNameException {
        // XXX uniq
        //        try {
            return new CompositeName( s );
//         } catch( InvalidNameException ex ) {
//             ex.printStackTrace();
//             return null;
//         }
    }
    



    //-------------------- Helpers -------------------- 

    /** Just a hack so that all DirContexts can be used as tasks.
     * They'll do nothing - the setters will be called ( just like
     * new Context(Hashtable) - since we use introspection ) and the
     * context can be registred as a reference in the Project ns.
     *
     * Then other tasks could manipulate it by name.
     *
     * In a future version of ant we should have the 'references'
     * pluggable and a possible impl should be JNDI.
     *
     * Alternative: there is a way to use tasks without this method,
     * but for now it's simpler.
     */
    public void execute() {
    }
    
}