session自己定义存储。怎样更好地进行session共享；





读tomcat源代码，org.apache.catalina.session.FileStore可知





一、详见：

方法1 public void save(Session session)

try {

            ((StandardSession)session).writeObjectData(oos);

        } finally {

            oos.close();

        }

方法2 public Session load(String id)

    ois = new ObjectInputStream(bis);





    StandardSession session = (StandardSession) manager.createEmptySession();

    session.readObjectData(ois);

    session.setManager(manager);

return (session);

二、在conf/context.xml文件设置：这个是针对全部的项目了。也能够针对详细项目来配置在server.xml中。

打开context.xml，在<Context>节点下加入例如以下<Manager>节点：

<Manager className="org.apache.catalina.session.PersistentManager" >

    debug=0

    saveOnRestart="true"

    maxActiveSession="-1"

    minIdleSwap="-1"

    maxIdleSwap="-1"

    maxIdleBackup="-1"

    <Store className="org.apache.catalina.session.FileStore" directory="../session" />

//这里代表的是文件持久化.也能够自己实现Store

</Manager>

三、源代码见下文

 * Licensed to the Apache Software Foundation (ASF) under one or more









package org.apache.catalina.session;









import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.util.ArrayList;





import javax.servlet.ServletContext;





import org.apache.catalina.Container;

import org.apache.catalina.Context;

import org.apache.catalina.Loader;

import org.apache.catalina.Session;

import org.apache.catalina.util.CustomObjectInputStream;









/**

 * Concrete implementation of the <b>Store</b> interface that utilizes

 * a file per saved Session in a configured directory.  Sessions that are

 * saved are still subject to being expired based on inactivity.

 *

 * @author Craig R. McClanahan

 */

public final class FileStore extends StoreBase {









    // ----------------------------------------------------- Constants









    /**

     * The extension to use for serialized session filenames.

     */

    private static final String FILE_EXT = ".session";









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









    /**

     * The pathname of the directory in which Sessions are stored.

     * This may be an absolute pathname, or a relative path that is

     * resolved against the temporary work directory for this application.

     */

    private String directory = ".";









    /**

     * A File representing the directory in which Sessions are stored.

     */

    private File directoryFile = null;









    /**

     * The descriptive information about this implementation.

     */

    private static final String info = "FileStore/1.0";





    /**

     * Name to register for this Store, used for logging.

     */

    private static final String storeName = "fileStore";





    /**

     * Name to register for the background thread.

     */

    private static final String threadName = "FileStore";









    // ------------------------------------------------------------- Properties









    /**

     * Return the directory path for this Store.

     */

    public String getDirectory() {





        return (directory);





    }









    /**

     * Set the directory path for this Store.

     *

     * @param path The new directory path

     */

    public void setDirectory(String path) {





        String oldDirectory = this.directory;

        this.directory = path;

        this.directoryFile = null;

        support.firePropertyChange("directory", oldDirectory,

                                   this.directory);





    }









    /**

     * Return descriptive information about this Store implementation and

     * the corresponding version number, in the format

     * <code>&lt;description&gt;/&lt;version&gt;</code>.

     */

    @Override

    public String getInfo() {





        return (info);





    }





    /**

     * Return the thread name for this Store.

     */

    public String getThreadName() {

        return(threadName);

    }





    /**

     * Return the name for this Store, used for logging.

     */

    @Override

    public String getStoreName() {

        return(storeName);

    }









    /**

     * Return the number of Sessions present in this Store.

     *

     * @exception IOException if an input/output error occurs

     */

    @Override

    public int getSize() throws IOException {





        // Acquire the list of files in our storage directory

        File file = directory();

        if (file == null) {

            return (0);

        }

        String files[] = file.list();





        // Figure out which files are sessions

        int keycount = 0;

        for (int i = 0; i < files.length; i++) {

            if (files[i].endsWith(FILE_EXT)) {

                keycount++;

            }

        }

        return (keycount);





    }









    // --------------------------------------------------------- Public Methods









    /**

     * Remove all of the Sessions in this Store.

     *

     * @exception IOException if an input/output error occurs

     */

    @Override

    public void clear()

        throws IOException {





        String[] keys = keys();

        for (int i = 0; i < keys.length; i++) {

            remove(keys[i]);

        }





    }









    /**

     * Return an array containing the session identifiers of all Sessions

     * currently saved in this Store.  If there are no such Sessions, a

     * zero-length array is returned.

     *

     * @exception IOException if an input/output error occurred

     */

    @Override

    public String[] keys() throws IOException {





        // Acquire the list of files in our storage directory

        File file = directory();

        if (file == null) {

            return (new String[0]);

        }





        String files[] = file.list();

        

        // Bugzilla 32130

        if((files == null) || (files.length < 1)) {

            return (new String[0]);

        }





        // Build and return the list of session identifiers

        ArrayList<String> list = new ArrayList<String>();

        int n = FILE_EXT.length();

        for (int i = 0; i < files.length; i++) {

            if (files[i].endsWith(FILE_EXT)) {

                list.add(files[i].substring(0, files[i].length() - n));

            }

        }

        return list.toArray(new String[list.size()]);





    }









    /**

     * Load and return the Session associated with the specified session

     * identifier from this Store, without removing it.  If there is no

     * such stored Session, return <code>null</code>.

     *

     * @param id Session identifier of the session to load

     *

     * @exception ClassNotFoundException if a deserialization error occurs

     * @exception IOException if an input/output error occurs

     */

    @Override

    public Session load(String id)

        throws ClassNotFoundException, IOException {





        // Open an input stream to the specified pathname, if any

        File file = file(id);

        if (file == null) {

            return (null);

        }





        if (! file.exists()) {

            return (null);

        }

        if (manager.getContainer().getLogger().isDebugEnabled()) {

            manager.getContainer().getLogger().debug(sm.getString(getStoreName()+".loading",

                             id, file.getAbsolutePath()));

        }





        FileInputStream fis = null;

        BufferedInputStream bis = null;

        ObjectInputStream ois = null;

        Loader loader = null;

        ClassLoader classLoader = null;

        ClassLoader oldThreadContextCL = Thread.currentThread().getContextClassLoader();

        try {

            fis = new FileInputStream(file.getAbsolutePath());

            bis = new BufferedInputStream(fis);

            Container container = manager.getContainer();

            if (container != null)

                loader = container.getLoader();

            if (loader != null)

                classLoader = loader.getClassLoader();

            if (classLoader != null) {

                Thread.currentThread().setContextClassLoader(classLoader);

                ois = new CustomObjectInputStream(bis, classLoader);

            } else {

                ois = new ObjectInputStream(bis);

            }





            StandardSession session =

                    (StandardSession) manager.createEmptySession();

            session.readObjectData(ois);

            session.setManager(manager);

            return (session);

        } catch (FileNotFoundException e) {

            if (manager.getContainer().getLogger().isDebugEnabled())

                manager.getContainer().getLogger().debug("No persisted data file found");

            return (null);

        } catch (IOException e) {

            if (bis != null) {

                try {

                    bis.close();

                } catch (IOException f) {

                    // Ignore

                }

            }

            if (fis != null) {

                try {

                    fis.close();

                } catch (IOException f) {

                    // Ignore

                }

            }

            throw e;

        } finally {

            if (ois != null) {

                // Close the input stream

                try {

                    ois.close();

                } catch (IOException f) {

                    // Ignore

                }

            }

            Thread.currentThread().setContextClassLoader(oldThreadContextCL);

        }

    }









    /**

     * Remove the Session with the specified session identifier from

     * this Store, if present.  If no such Session is present, this method

     * takes no action.

     *

     * @param id Session identifier of the Session to be removed

     *

     * @exception IOException if an input/output error occurs

     */

    @Override

    public void remove(String id) throws IOException {





        File file = file(id);

        if (file == null) {

            return;

        }

        if (manager.getContainer().getLogger().isDebugEnabled()) {

            manager.getContainer().getLogger().debug(sm.getString(getStoreName()+".removing",

                             id, file.getAbsolutePath()));

        }

        file.delete();





    }









    /**

     * Save the specified Session into this Store.  Any previously saved

     * information for the associated session identifier is replaced.

     *

     * @param session Session to be saved

     *

     * @exception IOException if an input/output error occurs

     */

    @Override

    public void save(Session session) throws IOException {





        // Open an output stream to the specified pathname, if any

        File file = file(session.getIdInternal());

        if (file == null) {

            return;

        }

        if (manager.getContainer().getLogger().isDebugEnabled()) {

            manager.getContainer().getLogger().debug(sm.getString(getStoreName()+".saving",

                             session.getIdInternal(), file.getAbsolutePath()));

        }

        FileOutputStream fos = null;

        ObjectOutputStream oos = null;

        try {

            fos = new FileOutputStream(file.getAbsolutePath());

            oos = new ObjectOutputStream(new BufferedOutputStream(fos));

        } catch (IOException e) {

            if (fos != null) {

                try {

                    fos.close();

                } catch (IOException f) {

                    // Ignore

                }

            }

            throw e;

        }





        try {

            ((StandardSession)session).writeObjectData(oos);

        } finally {

            oos.close();

        }





    }









    // -------------------------------------------------------- Private Methods









    /**

     * Return a File object representing the pathname to our

     * session persistence directory, if any.  The directory will be

     * created if it does not already exist.

     */

    private File directory() throws IOException {





        if (this.directory == null) {

            return (null);

        }

        if (this.directoryFile != null) {

            // NOTE:  Race condition is harmless, so do not synchronize

            return (this.directoryFile);

        }

        File file = new File(this.directory);

        if (!file.isAbsolute()) {

            Container container = manager.getContainer();

            if (container instanceof Context) {

                ServletContext servletContext =

                    ((Context) container).getServletContext();

                File work = (File)

                    servletContext.getAttribute(ServletContext.TEMPDIR);

                file = new File(work, this.directory);

            } else {

                throw new IllegalArgumentException

                    ("Parent Container is not a Context");

            }

        }

        if (!file.exists() || !file.isDirectory()) {

            if (!file.delete() && file.exists()) {

                throw new IOException(

                        sm.getString("fileStore.deleteFailed", file));

            }

            if (!file.mkdirs() && !file.isDirectory()) {

                throw new IOException(

                        sm.getString("fileStore.createFailed", file));

            }

        }

        this.directoryFile = file;

        return (file);





    }









    /**

     * Return a File object representing the pathname to our

     * session persistence file, if any.

     *

     * @param id The ID of the Session to be retrieved. This is

     *    used in the file naming.

     */

    private File file(String id) throws IOException {





        if (this.directory == null) {

            return (null);

        }

        String filename = id + FILE_EXT;

        File file = new File(directory(), filename);

        return (file);





    }









}