jdbc.sgml

关系型数据库 Postgresql 6.5.2

Oh, one last thing. If your object contains a line like:

     public int oid;

then, when the object is retrieved from the table, it is set to the 
oid within the table. Then, if the object is modified, and re-
serialized, the existing entry is updated.

If the oid variable is not present, then when the object is 
serialized, it is always inserted into the table, and any existing 
entry in the table is preserved.

Setting oid to 0 before serialization, will also cause the object to 
be inserted. This enables an object to be duplicated in the database.

Class postgresql.util.Serialize

java.lang.Object
   |
   +----postgresql.util.Serialize

   public class Serialize extends Object

   This class uses PostgreSQL's object oriented features to store Java 
Objects. It does this by mapping a Java Class name to a table in the 
database. Each entry in this new table then represents a Serialized 
instance of this class. As each entry has an OID (Object IDentifier), 
this OID can be included in another table. This is too complex to show 
here, and will be documented in the main documents in more detail.

Constructors

 public Serialize(Connection c,
                  String type) throws SQLException

          This creates an instance that can be used to serialize 
ordeserialize a Java object from a PostgreSQL table.

Methods

 public Object fetch(int oid) throws SQLException

          This fetches an object from a table, given it's OID

        Parameters:
                oid - The oid of the object

        Returns:
                Object relating to oid

        Throws: SQLException
                on error

 public int store(Object o) throws SQLException

          This stores an object into a table, returning it's OID.

          If the object has an int called OID, and it is > 0, then 
that value is used for the OID, and the table will be updated. If the 
value of OID is 0, then a new row will be created, and the value of 
OID will be set in the object. This enables an object's value in the 
database to be updateable. If the object has no int called OID, then 
the object is stored. However if the object is later retrieved, 
amended and stored again, it's new state will be appended to the 
table, and will not overwrite the old entries.

        Parameters:
                o - Object to store (must implement Serializable)

        Returns:
                oid of stored object

        Throws: SQLException
                on error
 
 public static void create(Connection con,
                           Object o) throws SQLException

          This method is not used by the driver, but it creates a 
table, given a Serializable Java Object. It should be used before 
serializing any objects.

        Parameters:
                c - Connection to database
                o - Object to base table on

        Throws: SQLException
                on error

                   Returns:
                Object relating to oid

        Throws: SQLException
                on error

 public int store(Object o) throws SQLException

          This stores an object into a table, returning it's OID.

          If the object has an int called OID, and it is > 0, then 
that value is used for the OID, and the table will be updated. If the 
value of OID is 0, then a new row will be created, and the value of 
OID will be set in the object. This enables an object's value in the 
database to be updateable. If the object has no int called OID, then 
the object is stored. However if the object is later retrieved, 
amended and stored again, it's new state will be appended to the 
table, and will not overwrite the old entries.

        Parameters:
                o - Object to store (must implement Serializable)

        Returns:
                oid of stored object

        Throws: SQLException
                on error
 
 public static void create(Connection con,
                           Object o) throws SQLException

          This method is not used by the driver, but it creates a 
table, given a Serializable Java Object. It should be used before 
serializing any objects.

        Parameters:
                c - Connection to database
                o - Object to base table on

        Throws: SQLException
                on error
                
 public static void create(Connection con,
                           Class c) throws SQLException

          This method is not used by the driver, but it creates a 
table, given a Serializable Java Object. It should be used before 
serializing any objects.

        Parameters:
                c - Connection to database
                o - Class to base table on

        Throws: SQLException
                on error

 public static String toPostgreSQL(String name) throws SQLException
          
          This converts a Java Class name to a postgresql table, by
          replacing . with _

          Because of this, a Class name may not have _ in the name.

          Another limitation, is that the entire class name (including
          packages) cannot be longer than 31 characters (a limit 
forced by PostgreSQL).

        Parameters:
                name - Class name

        Returns:
                PostgreSQL table name

        Throws: SQLException
                on error
          
 public static String toClassName(String name) throws SQLException

          This converts a postgresql table to a Java Class name, by
          replacing _ with .

        Parameters:
                name - PostgreSQL table name
  
        Returns:
                Class name

        Throws: SQLException
                on error

Utility Classes

The postgresql.util package contains classes used by the internals of 
the main driver, and the other extensions.

Class postgresql.util.PGmoney
                                
java.lang.Object
   |
   +----postgresql.util.PGobject
           |
           +----postgresql.util.PGmoney

   public class PGmoney extends PGobject implements Serializable, 
Cloneable
               
   This implements a class that handles the PostgreSQL money type

Variables

 public double val
                                
          The value of the field

Constructors
           
 public PGmoney(double value)
   
        Parameters:
                value - of field
               
 public PGmoney(String value) throws SQLException
   
          This is called mainly from the other geometric types, when a 
point is imbeded within their definition.

        Parameters:
                value - Definition of this point in PostgreSQL's 
syntax

 public PGmoney()

          Required by the driver

Methods

 public void setValue(String s) throws SQLException

        Parameters:
                s - Definition of this point in PostgreSQL's syntax

        Throws: SQLException
                on conversion failure

        Overrides:
                setValue in class PGobject

 public boolean equals(Object obj)

        Parameters:
                obj - Object to compare with
                                
        Returns:
                true if the two boxes are identical

        Overrides:
                equals in class PGobject

 public Object clone()
                
          This must be overidden to allow the object to be cloned

        Overrides:
                clone in class PGobject

 public String getValue()

        Returns:
                the PGpoint in the syntax expected by postgresql

        Overrides:
                getValue in class PGobject

Class postgresql.util.PGobject

java.lang.Object
   |
   +----postgresql.util.PGobject

   public class PGobject extends Object implements Serializable, 
Cloneable
               
   This class is used to describe data types that are unknown by <acronym>JDBC</acronym> 
Standard.
    A call to postgresql.Connection permits a class that extends this 
class to be associated with a named type. This is how the 
postgresql.geometric package operates.
    ResultSet.getObject() will return this class for any type that is 
not recognised on having it's own handler. Because of this, any 
postgresql data type is supported.

Constructors

 public PGobject()

          This is called by postgresql.Connection.getObject() to 
create the object.

Methods

 public final void setType(String type)

          This method sets the type of this object.

          It should not be extended by subclasses, hence its final

        Parameters:
                type - a string describing the type of the object

 public void setValue(String value) throws SQLException

          This method sets the value of this object. It must be 
overidden.

        Parameters:
                value - a string representation of the value of the
                object

        Throws: SQLException
                thrown if value is invalid for this type
    
 public final String getType()

          As this cannot change during the life of the object, it's 
final.

        Returns:
                the type name of this object

 public String getValue()

          This must be overidden, to return the value of the object, 
in the form required by postgresql.

        Returns:
                the value of this object

 public boolean equals(Object obj)

          This must be overidden to allow comparisons of objects

        Parameters:
                obj - Object to compare with

        Returns:
                true if the two boxes are identical

        Overrides:
                equals in class Object

 public Object clone()

          This must be overidden to allow the object to be cloned

        Overrides:
                clone in class Object

 public String toString()

          This is defined here, so user code need not overide it.
          
        Returns:
                the value of this object, in the syntax expected by 
postgresql

        Overrides:
                toString in class Object

Class postgresql.util.PGtokenizer

java.lang.Object
   |
   +----postgresql.util.PGtokenizer

   public class PGtokenizer extends Object

   This class is used to tokenize the text output of postgres.

   We could have used StringTokenizer to do this, however, we needed 
to handle nesting of '(' ')' '[' ']' '<' and '>' as these are used by 
the geometric data types.

   It's mainly used by the geometric classes, but is useful in parsing 
any output from custom data types output from postgresql.
                 
   See Also:
          PGbox, PGcircle, PGlseg, PGpath, PGpoint, PGpolygon
          
Constructors

 public PGtokenizer(String string,
                    char delim)

          Create a tokeniser.

        Parameters:
                string - containing tokens
                delim - single character to split the tokens

Methods
        
 public int tokenize(String string,
                     char delim)

          This resets this tokenizer with a new string and/or 
delimiter.

        Parameters:
                string - containing tokens
                delim - single character to split the tokens

 public int getSize()

        Returns:
                the number of tokens available

 public String getToken(int n)

        Parameters:
                n - Token number ( 0 ... getSize()-1 )

        Returns:
                The token value

 public PGtokenizer tokenizeToken(int n,
                                  char delim)

          This returns a new tokenizer based on one of our tokens. The 
geometric datatypes use this to process nested tokens (usually 
PGpoint).

        Parameters:
                n - Token number ( 0 ... getSize()-1 )
                delim - The delimiter to use

        Returns:
                A new instance of PGtokenizer based on the token

 public static String remove(String s,
                             String l,
                             String t)

          This removes the lead/trailing strings from a string

        Parameters:
                s - Source string
                l - Leading string to remove
                t - Trailing string to remove
                
        Returns:
                String without the lead/trailing strings

 public void remove(String l,
                    String t)

          This removes the lead/trailing strings from all tokens

        Parameters:
                l - Leading string to remove
                t - Trailing string to remove

 public static String removePara(String s)

          Removes ( and ) from the beginning and end of a string

        Parameters:
                s - String to remove from

        Returns:
                String without the ( or )

 public void removePara()

          Removes ( and ) from the beginning and end of all tokens

        Returns:
                String without the ( or )

 public static String removeBox(String s)
   
          Removes [ and ] from the beginning and end of a string

        Parameters:
                s - String to remove from
   
        Returns:
                String without the [ or ]

 public void removeBox()

          Removes [ and ] from the beginning and end of all tokens

        Returns:
                String without the [ or ]

 public static String removeAngle(String s)

          Removes < and > from the beginning and end of a string

        Parameters:
                s - String to remove from

        Returns:
                Strin