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Re: JDBC - DatabaseMetaData.getTables() null pointer exception

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: dantal(at)vigilos(dot)com, pgsql-bugs(at)postgresql(dot)org
Subject: Re: JDBC - DatabaseMetaData.getTables() null pointer exception
Date: 2001-07-12 22:42:12
Message-ID: 200107122242.f6CMgCE13988@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
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This bug is fixed.


> Dave Antal (dantal(at)vigilos(dot)com) reports a bug with a severity of 2
> The lower the number the more severe it is.
> 
> Short Description
> JDBC - DatabaseMetaData.getTables() null pointer exception
> 
> Long Description
> When you pass the DatabaseMetaData.getTables() method a types array that contains "VIEW" a null pointer exception is generated. This is in the JDBC driver that is with Postgres 7.1.2.  This is caused by the code not checking for a View type on the relkind column returned from the select of pg_class. The code example below contains a version of the method with a fix in place.
> 
> Sample Code
>   /**
>    * Get a description of tables available in a catalog.
>    *
>    * <p>Only table descriptions matching the catalog, schema, table
>    * name and type criteria are returned. They are ordered by
>    * TABLE_TYPE, TABLE_SCHEM and TABLE_NAME.
>    *
>    * <p>Each table description has the following columns:
>    *
>    * <ol>
>    * <li><b>TABLE_CAT</b> String => table catalog (may be null)
>    * <li><b>TABLE_SCHEM</b> String => table schema (may be null)
>    * <li><b>TABLE_NAME</b> String => table name
>    * <li><b>TABLE_TYPE</b> String => table type. Typical types are "TABLE",
>    * "VIEW", "SYSTEM TABLE", "GLOBAL TEMPORARY", "LOCAL
>    * TEMPORARY", "ALIAS", "SYNONYM".
>    * <li><b>REMARKS</b> String => explanatory comment on the table
>    * </ol>
>    *
>    * <p>The valid values for the types parameter are:
>    * "TABLE", "INDEX", "SEQUENCE", "SYSTEM TABLE" and "SYSTEM INDEX"
>    *
>    * @param catalog a catalog name; For org.postgresql, this is ignored, and
>    * should be set to null
>    * @param schemaPattern a schema name pattern; For org.postgresql, this is ignored, and
>    * should be set to null
>    * @param tableNamePattern a table name pattern. For all tables this should be "%"
>    * @param types a list of table types to include; null returns
>    * all types
>    * @return each row is a table description
>    * @exception SQLException if a database-access error occurs.
>    */
>   public java.sql.ResultSet getTables(String catalog, String schemaPattern, String tableNamePattern, String types[]) throws SQLException
>   {
>     // Handle default value for types
>     if(types==null)
>       types = defaultTableTypes;
> 
>     if(tableNamePattern==null)
>       tableNamePattern="%";
> 
>     // the field descriptors for the new ResultSet
>     Field f[] = new Field[5];
>     java.sql.ResultSet r;	// ResultSet for the SQL query that we need to do
>     Vector v = new Vector();		// The new ResultSet tuple stuff
> 
>     f[0] = new Field(connection, "TABLE_CAT", iVarcharOid, 32);
>     f[1] = new Field(connection, "TABLE_SCHEM", iVarcharOid, 32);
>     f[2] = new Field(connection, "TABLE_NAME", iVarcharOid, 32);
>     f[3] = new Field(connection, "TABLE_TYPE", iVarcharOid, 32);
>     f[4] = new Field(connection, "REMARKS", iVarcharOid, 32);
> 
>     // Now form the query
>     StringBuffer sql = new StringBuffer("select relname,oid,relkind from pg_class where (");
>     boolean notFirst=false;
>     for(int i=0;i<types.length;i++) {
>       for(int j=0;j<getTableTypes.length;j++)
> 	if(getTableTypes[j][0].equals(types[i])) {
> 	  if(notFirst)
> 	    sql.append(" or ");
> 	  sql.append(getTableTypes[j][1]);
> 	  notFirst=true;
> 	}
>     }
> 
>     // Added by Stefan Andreasen <stefan(at)linux(dot)kapow(dot)dk>
>     // Now take the pattern into account
>     sql.append(") and relname like '");
>     sql.append(tableNamePattern.toLowerCase());
>     sql.append("'");
> 
>     // Now run the query
>     r = connection.ExecSQL(sql.toString());
> 
>     byte remarks[];
> 
>     while (r.next())
>       {
> 	byte[][] tuple = new byte[5][0];
> 
> 	// Fetch the description for the table (if any)
> 	java.sql.ResultSet dr = connection.ExecSQL("select description from pg_description where objoid="+r.getInt(2));
> 	if(((org.postgresql.ResultSet)dr).getTupleCount()==1) {
> 	  dr.next();
> 	  remarks = dr.getBytes(1);
> 	} else
> 	  remarks = defaultRemarks;
> 	dr.close();
> 
> 	String relKind;
> 	switch (r.getBytes(3)[0]) {
> 	case 'r':
> 	    relKind = "TABLE";
> 	    break;
> 	case 'i':
> 	    relKind = "INDEX";
> 	    break;
> 	case 'S':
> 	    relKind = "SEQUENCE";
> 	    break;
> 	case 'v':
> 	    relKind = "VIEW";
> 	    break;
> 	default:
> 	    relKind = null;
> 	}
> 
> 	tuple[0] = null;		// Catalog name
> 	tuple[1] = null;		// Schema name
> 	tuple[2] = r.getBytes(1);	// Table name
> 	tuple[3] = relKind.getBytes();	// Table type
> 	tuple[4] = remarks;		// Remarks
> 	v.addElement(tuple);
>       }
>     r.close();
>     return new ResultSet(connection, f, v, "OK", 1);
>   }
> 
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> 
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-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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