Docjar: org/vrspace/server/DB.java

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Source code: org/vrspace/server/DB.java

1   package org.vrspace.server;
2   import java.io.*;
3   import java.net.*;
4   import org.vrspace.util.*;
5   import org.vrspace.server.db.DBCache;
6   /**
7    * Database class
8    * 
9   */
10  public abstract class DB {
11  
12    /** this keeps reference to cache */
13    public DBCache cache;
14    
15    /** 
16    create a new database if does not exist
17    @param name Database name
18    @return String to use as parameter to connect()
19    @see #connect
20    */
21    public abstract String create( String name ) throws Exception;
22    
23    /** connect to the database */
24    public abstract void connect ( String url ) throws Exception;
25    
26    /** Disconnect from the database **/
27    public abstract void disconnect();
28    
29    /**
30    Commit changes. Should NOT be synchronized.
31    */
32    public abstract void commit();
33    
34    /** Return database object from table <b>obj</b>.getClass().getName() having
35     ** db_id = <b>obj</b>.db_id
36     */
37    public abstract Object get( Object obj ) throws Exception;
38  
39    /** Returns the object having id == <b>obj</b>.db_id
40    */
41    public abstract Object get( String className, long id ) throws Exception;
42  
43    /** Returns the object of <b>className</b> class having <b>field</b> == <b>value</b> */
44    public abstract Object get( String className, String field, Object value )
45                           throws Exception;
46  
47    /** Returns the object of <b>className</b> class having <b>field</b> == <b>value</b> */
48    public abstract Object[] getRange( String className, String field, Object value )
49                           throws Exception;
50  
51    /** 
52    Returns Object[] between o1 and o2
53    Class must have comparator() method to be searchable.
54    */
55    public abstract Object[] getRange( Object o1, Object o2 )
56                    throws Exception;
57  
58    /**
59    Returns all members of the class
60    */
61    public abstract Object[] getAll( String className ) throws Exception;
62  
63    /** From the table <b>obj</b>.getClass().getName() deletes the row having
64     ** db_id == <b>obj</b>.db_id
65     */
66    public abstract void delete( Object obj ) throws Exception;
67  
68    /** 
69    Stores obj into database
70    Logic: 
71      - all the public fields are stored
72      - database table: obj.getClass().getName()
73      - create table if does not exist
74    */
75    public abstract void put( Object obj ) throws Exception;
76  
77    /**
78    A request is a change to <b>one</b> field. This method allows
79    optimal database update.
80    */
81    public abstract void update( Request r ) throws Exception;
82    
83    /**
84    Loads file content into the db. Default protocol for <b>url</b> is 'file'
85    */
86    public void load( String url ) throws Exception {
87      URL u;
88      try {
89        u = new URL( url );
90      } catch (MalformedURLException e) {
91        url = "file:"+url;
92        try {
93          u = new URL( url );
94        } catch ( MalformedURLException e1 ) {
95          throw e;
96        }
97      }
98      InputStream in = u.openStream();
99      load( new InputStreamReader(in) );
100   }
101   /**
102   Loads stream content into the database
103   */
104   public void load( Reader in ) throws Exception {
105     BufferedReader reader = new BufferedReader( in );
106     String line;
107     StringBuffer text = new StringBuffer();
108     long time = System.currentTimeMillis();
109     while ( ( line = reader.readLine() ) != null ) {
110       text.append(line + "\n");
111     }
112     Object[] objects = VRObject.fromText( text.toString() );
113     time = System.currentTimeMillis()-time;
114     Logger.logDebug( "DB: "+objects.length+" objects loaded in "+time/100+" seconds" );
115     for ( int i = 0; i < objects.length; i++ ) {
116       //Logger.logDebug( objects[i].toString() );
117       ((VRObject)objects[i]).isNew = true;
118       if ( (cache != null ) ) {
119         cache.put( objects[ i ] );
120       } else {
121         put( objects[ i ] );
122       }
123       ((VRObject)objects[i]).isNew = false;
124     }
125   }
126   /**
127   Loads file content into the database
128   */
129   public void load( File file ) throws Exception {
130     load( new FileReader( file ));
131   }
132 }