Postgres is an extensible database system. You can add your own functions to the backend, which can then be called from queries, or even add your own data types. As these are facilities unique to Postgres, we support them from Java, with a set of extension API's. Some features within the core of the standard driver actually use these extensions to implement Large Objects, etc.
To access some of the extensions, you need to use some extra methods in the org.postgresql.Connection class. In this case, you would need to case the return value of Driver.getConnection(). For example:
Connection db = Driver.getConnection(url, username, password); // ... // later on Fastpath fp = ((org.postgresql.Connection)db).getFastpathAPI();
public class Connection extends Object implements Connection java.lang.Object | +----org.postgresql.Connection
These are the extra methods used to gain access to PostgreSQL's extensions. Methods defined by java.sql.Connection are not listed.
public Fastpath getFastpathAPI() throws SQLException
This returns the Fastpath API for the current connection. It is primarily used by the Large Object API.
The best way to use this is as follows:
import org.postgresql.fastpath.*; ... Fastpath fp = ((org.postgresql.Connection)myconn).getFastpathAPI();where myconn is an open Connection to PostgreSQL.
Returns: Fastpath object allowing access to functions on the PostgreSQL backend.
Throws: SQLException by Fastpath when initializing for first time
public LargeObjectManager getLargeObjectAPI() throws SQLExceptionThis returns the Large Object API for the current connection.
The best way to use this is as follows:
import org.postgresql.largeobject.*; ... LargeObjectManager lo = ((org.postgresql.Connection)myconn).getLargeObjectAPI();where myconn is an open Connection to PostgreSQL.
Returns: LargeObject object that implements the API
Throws: SQLException by LargeObject when initializing for first time
public void addDataType(String type, String name)This allows client code to add a handler for one of PostgreSQL's more unique data types. Normally, a data type not known by the driver is returned by ResultSet.getObject() as a PGobject instance. This method allows you to write a class that extends PGobject, and tell the driver the type name, and class name to use. The down side to this, is that you must call this method each time a connection is made.
The best way to use this is as follows:
...
((org.postgresql.Connection)myconn).addDataType("mytype","my.class.name");
...
where myconn is an open Connection to
PostgreSQL. The
handling class must extend org.postgresql.util.PGobject.
public class Fastpath extends Object java.lang.Object | +----org.postgresql.fastpath.Fastpath
Fastpath is an API that exists within the libpq C interface, and allows a client machine to execute a function on the database backend. Most client code will not need to use this method, but it is provided because the Large Object API uses it.
To use, you need to import the org.postgresql.fastpath package, using the line:
import org.postgresql.fastpath.*;Then, in your code, you need to get a FastPath object:
Fastpath fp = ((org.postgresql.Connection)conn).getFastpathAPI();This will return an instance associated with the database connection that you can use to issue commands. The casing of Connection to org.postgresql.Connection is required, as the getFastpathAPI() is an extension method, not part of JDBC. Once you have a Fastpath instance, you can use the fastpath() methods to execute a backend function.
See Also: FastpathFastpathArg, LargeObject
public Object fastpath(int fnid,
boolean resulttype,
FastpathArg args[]) throws SQLException
Send a function call to the PostgreSQL backend.
Parameters: fnid - Function id resulttype - True if the result is an integer, false for other results args - FastpathArguments to pass to fastpath
Returns: null if no data, Integer if an integer result, or byte[] otherwise
public Object fastpath(String name,
boolean resulttype,
FastpathArg args[]) throws SQLException
Send a function call to the PostgreSQL backend by name.
Note: The mapping for the procedure name to function id needs to exist, usually to an earlier call to addfunction(). This is the preferred method to call, as function id's can/may change between versions of the backend. For an example of how this works, refer to org.postgresql.LargeObject
Parameters: name - Function name resulttype - True if the result is an integer, false for other results args - FastpathArguments to pass to fastpath
Returns: null if no data, Integer if an integer result, or byte[] otherwise
See Also: LargeObject
public int getInteger(String name,
FastpathArg args[]) throws SQLException
This convenience method assumes that the return value is an Integer
Parameters: name - Function name args - Function arguments
Returns: integer result
Throws: SQLException if a database-access error occurs or no result
public byte[] getData(String name,
FastpathArg args[]) throws SQLException
This convenience method assumes that the return value is binary data.
Parameters: name - Function name args - Function arguments
Returns: byte[] array containing result
Throws: SQLException if a database-access error occurs or no result
public void addFunction(String name,
int fnid)
This adds a function to our look-up table. User code should use the addFunctions method, which is based upon a query, rather than hard coding the oid. The oid for a function is not guaranteed to remain static, even on different servers of the same version.
public void addFunctions(ResultSet rs) throws SQLException
This takes a ResultSet containing two columns. Column 1 contains the function name, Column 2 the oid. It reads the entire ResultSet, loading the values into the function table.
Important: Remember to close() the ResultSet after calling this!
Implementation note about function name look-ups: PostgreSQL stores the function id's and their corresponding names in the pg_proc table. To speed things up locally, instead of querying each function from that table when required, a Hashtable is used. Also, only the function's required are entered into this table, keeping connection times as fast as possible.
The org.postgresql.LargeObject class performs a query upon its start-up, and passes the returned ResultSet to the addFunctions() method here. Once this has been done, the Large Object API refers to the functions by name.
Do not think that manually converting them to the oid's will work. Okay, they will for now, but they can change during development (there was some discussion about this for V7.0), so this is implemented to prevent any unwarranted headaches in the future.
See Also: LargeObjectManager
public int getID(String name) throws SQLException
This returns the function id associated by its name If addFunction() or addFunctions() have not been called for this name, then an SQLException is thrown.
public class FastpathArg extends Object java.lang.Object | +----org.postgresql.fastpath.FastpathArg
Each fastpath call requires an array of arguments, the number and type dependent on the function being called. This class implements methods needed to provide this capability.
For an example on how to use this, refer to the org.postgresql.LargeObject package.
See Also: Fastpath, LargeObjectManager, LargeObject
public FastpathArg(int value)
Constructs an argument that consists of an integer value
Parameters: value - int value to set
public FastpathArg(byte bytes[])
Constructs an argument that consists of an array of bytes
Parameters: bytes - array to store
public FastpathArg(byte buf[],
int off,
int len)
Constructs an argument that consists of part of a byte array
Parameters:
source array
offset within array
length of data to include
public FastpathArg(String s)
Constructs an argument that consists of a String.
PostgreSQL has a set of data types that can store geometric features into a table. These include single points, lines, and polygons. We support these types in Java with the org.postgresql.geometric package. It contains classes that extend the org.postgresql.util.PGobject class. Refer to that class for details on how to implement your own data type handlers.
Class org.postgresql.geometric.PGbox
java.lang.Object
|
+----org.postgresql.util.PGobject
|
+----org.postgresql.geometric.PGbox
public class PGbox extends PGobject implements Serializable,
Cloneable
This represents the box data type within PostgreSQL.
Variables
public PGpoint point[]
These are the two corner points of the box.
Constructors
public PGbox(double x1,
double y1,
double x2,
double y2)
Parameters:
x1 - first x coordinate
y1 - first y coordinate
x2 - second x coordinate
y2 - second y coordinate
public PGbox(PGpoint p1,
PGpoint p2)
Parameters:
p1 - first point
p2 - second point
public PGbox(String s) throws SQLException
Parameters:
s - Box definition in PostgreSQL syntax
Throws: SQLException
if definition is invalid
public PGbox()
Required constructor
Methods
public void setValue(String value) throws SQLException
This method sets the value of this object. It should be
overridden, but still called by subclasses.
Parameters:
value - a string representation of the value of the
object
Throws: SQLException
thrown if value is invalid for this type
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 overridden to allow the object to be cloned
Overrides:
clone in class PGobject
public String getValue()
Returns:
the PGbox in the syntax expected by PostgreSQL
Overrides:
getValue in class PGobject
Class org.postgresql.geometric.PGcircle
java.lang.Object
|
+----org.postgresql.util.PGobject
|
+----org.postgresql.geometric.PGcircle
public class PGcircle extends PGobject implements Serializable,
Cloneable
This represents PostgreSQL's circle data type, consisting of a point
and a radius
Variables
public PGpoint center
This is the center point
public double radius
This is the radius
Constructors
public PGcircle(double x,
double y,
double r)
Parameters:
x - coordinate of center
y - coordinate of center
r - radius of circle
public PGcircle(PGpoint c,
double r)
Parameters:
c - PGpoint describing the circle's center
r - radius of circle
public PGcircle(String s) throws SQLException
Parameters:
s - definition of the circle in PostgreSQL's syntax.
Throws: SQLException
on conversion failure
public PGcircle()
This constructor is used by the driver.
Methods
public void setValue(String s) throws SQLException
Parameters:
s - definition of the circle 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 overridden to allow the object to be cloned
Overrides:
clone in class PGobject
public String getValue()
Returns:
the PGcircle in the syntax expected by PostgreSQL
Overrides:
getValue in class PGobject
Class org.postgresql.geometric.PGline
java.lang.Object
|
+----org.postgresql.util.PGobject
|
+----org.postgresql.geometric.PGline
public class PGline extends PGobject implements Serializable,
Cloneable
This implements a line consisting of two points. Currently line is
not yet implemented in the backend, but this class ensures that when
it's done were ready for it.
Variables
public PGpoint point[]
These are the two points.
Constructors
public PGline(double x1,
double y1,
double x2,
double y2)
Parameters:
x1 - coordinate for first point
y1 - coordinate for first point
x2 - coordinate for second point
y2 - coordinate for second point
public PGline(PGpoint p1,
PGpoint p2)
Parameters:
p1 - first point
p2 - second point
public PGline(String s) throws SQLException
Parameters:
s - definition of the circle in PostgreSQL's syntax.
Throws: SQLException
on conversion failure
public PGline()
required by the driver
Methods
public void setValue(String s) throws SQLException
Parameters:
s - Definition of the line segment 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 overridden to allow the object to be cloned
Overrides:
clone in class PGobject
public String getValue()
Returns:
the PGline in the syntax expected by PostgreSQL
Overrides:
getValue in class PGobject
Class org.postgresql.geometric.PGlseg
java.lang.Object
|
+----org.postgresql.util.PGobject
|
+----org.postgresql.geometric.PGlseg
public class PGlseg extends PGobject implements Serializable,
Cloneable
This implements a lseg (line segment) consisting of two points
Variables
public PGpoint point[]
These are the two points.
Constructors
public PGlseg(double x1,
double y1,
double x2,
double y2)
Parameters:
x1 - coordinate for first point
y1 - coordinate for first point
x2 - coordinate for second point
y2 - coordinate for second point
public PGlseg(PGpoint p1,
PGpoint p2)
Parameters:
p1 - first point
p2 - second point
public PGlseg(String s) throws SQLException
Parameters:
s - definition of the circle in PostgreSQL's syntax.
Throws: SQLException
on conversion failure
public PGlseg()
required by the driver
Methods
public void setValue(String s) throws SQLException
Parameters:
s - Definition of the line segment 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 overridden to allow the object to be cloned
Overrides:
clone in class PGobject
public String getValue()
Returns:
the PGlseg in the syntax expected by PostgreSQL
Overrides:
getValue in class PGobject
Class org.postgresql.geometric.PGpath
java.lang.Object
|
+----org.postgresql.util.PGobject
|
+----org.postgresql.geometric.PGpath
public class PGpath extends PGobject implements Serializable,
Cloneable
This implements a path (a multiply segmented line, which may be
closed)
Variables
public boolean open
True if the path is open, false if closed
public PGpoint points[]
The points defining this path
Constructors
public PGpath(PGpoint points[],
boolean open)
Parameters:
points - the PGpoints that define the path
open - True if the path is open, false if closed
public PGpath()
Required by the driver
public PGpath(String s) throws SQLException
Parameters:
s - definition of the circle in PostgreSQL's syntax.
Throws: SQLException
on conversion failure
Methods
public void setValue(String s) throws SQLException
Parameters:
s - Definition of the path 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 overridden to allow the object to be cloned
Overrides:
clone in class PGobject
public String getValue()
This returns the polygon in the syntax expected by
PostgreSQL
Overrides:
getValue in class PGobject
public boolean isOpen()
This returns true if the path is open
public boolean isClosed()
This returns true if the path is closed
public void closePath()
Marks the path as closed
public void openPath()
Marks the path as open
Class org.postgresql.geometric.PGpoint
java.lang.Object
|
+----org.postgresql.util.PGobject
|
+----org.postgresql.geometric.PGpoint
public class PGpoint extends PGobject implements Serializable,
Cloneable
This implements a version of java.awt.Point, except it uses double
to represent the coordinates.
It maps to the point data type in PostgreSQL.
Variables
public double x
The X coordinate of the point
public double y
The Y coordinate of the point
Constructors
public PGpoint(double x,
double y)
Parameters:
x - coordinate
y - coordinate
public PGpoint(String value) throws SQLException
This is called mainly from the other geometric types, when a
point is embedded within their definition.
Parameters:
value - Definition of this point in PostgreSQL's
syntax
public PGpoint()
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 overridden 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
public void translate(int x,
int y)
Translate the point with the supplied amount.
Parameters:
x - integer amount to add on the x axis
y - integer amount to add on the y axis
public void translate(double x,
double y)
Translate the point with the supplied amount.
Parameters:
x - double amount to add on the x axis
y - double amount to add on the y axis
public void move(int x,
int y)
Moves the point to the supplied coordinates.
Parameters:
x - integer coordinate
y - integer coordinate
public void move(double x,
double y)
Moves the point to the supplied coordinates.
Parameters:
x - double coordinate
y - double coordinate
public void setLocation(int x,
int y)
Moves the point to the supplied coordinates. refer to
java.awt.Point for description of this
Parameters:
x - integer coordinate
y - integer coordinate
See Also:
Point
public void setLocation(Point p)
Moves the point to the supplied java.awt.Point refer to
java.awt.Point for description of this
Parameters:
p - Point to move to
See Also:
Point
Class org.postgresql.geometric.PGpolygon
java.lang.Object
|
+----org.postgresql.util.PGobject
|
+----org.postgresql.geometric.PGpolygon
public class PGpolygon extends PGobject implements Serializable,
Cloneable
This implements the polygon data type within PostgreSQL.
Variables
public PGpoint points[]
The points defining the polygon
Constructors
public PGpolygon(PGpoint points[])
Creates a polygon using an array of PGpoints
Parameters:
points - the points defining the polygon
public PGpolygon(String s) throws SQLException
Parameters:
s - definition of the circle in PostgreSQL's syntax.
Throws: SQLException
on conversion failure
public PGpolygon()
Required by the driver
Methods
public void setValue(String s) throws SQLException
Parameters:
s - Definition of the polygon 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 overridden to allow the object to be cloned
Overrides:
clone in class PGobject
public String getValue()
Returns:
the PGpolygon in the syntax expected by PostgreSQL
Overrides:
getValue in class PGobject
Large objects are supported in the standard JDBC specification. However, that interface is limited, and the API provided by PostgreSQL allows for random access to the objects contents, as if it was a local file.
The org.postgresql.largeobject package provides to Java the libpq C interface's large object API. It consists of two classes, LargeObjectManager, which deals with creating, opening and deleting large objects, and LargeObject which deals with an individual object.
public class LargeObject extends Object java.lang.Object | +----org.postgresql.largeobject.LargeObject
This class implements the large object interface to PostgreSQL.
It provides the basic methods required to run the interface, plus a pair of methods that provide InputStream and OutputStream classes for this object.
Normally, client code would use the getAsciiStream, getBinaryStream, or getUnicodeStream methods in ResultSet, or setAsciiStream, setBinaryStream, or setUnicodeStream methods in PreparedStatement to access Large Objects.
However, sometimes lower level access to Large Objects are required, that are not supported by the JDBC specification.
Refer to org.postgresql.largeobject.LargeObjectManager on how to gain access to a Large Object, or how to create one.
See Also: LargeObjectManager
Indicates a seek from the beginning of a file
Indicates a seek from the current position
Indicates a seek from the end of a file
public int getOID()
Returns the OID of this LargeObject
public void close() throws SQLException
This method closes the object. You must not call methods in this object after this is called.
public byte[] read(int len) throws SQLException
Reads some data from the object, and return as a byte[] array
public void read(byte buf[],
int off,
int len) throws SQLException
Reads some data from the object into an existing array
Parameters:
destination array
offset within array
number of bytes to read
public void write(byte buf[]) throws SQLException
Writes an array to the object
public void write(byte buf[],
int off,
int len) throws SQLException
Writes some data from an array to the object
Parameters:
destination array
offset within array
number of bytes to write
public class LargeObjectManager extends Object
java.lang.Object
|
+----org.postgresql.largeobject.LargeObjectManager
This class implements the large object interface to PostgreSQL. It provides methods that allow client code to create, open and delete large objects from the database. When opening an object, an instance of org.postgresql.largeobject.LargeObject is returned, and its methods then allow access to the object.
This class can only be created by org.postgresql.Connection. To get access to this class, use the following segment of code:
import org.postgresql.largeobject.*; Connection conn; LargeObjectManager lobj; // ... code that opens a connection ... lobj = ((org.postgresql.Connection)myconn).getLargeObjectAPI();
Normally, client code would use the getAsciiStream, getBinaryStream, or getUnicodeStream methods in ResultSet, or setAsciiStream, setBinaryStream, or setUnicodeStream methods in PreparedStatement to access Large Objects. However, sometimes lower level access to Large Objects are required, that are not supported by the JDBC specification.
Refer to org.postgresql.largeobject.LargeObject on how to manipulate the contents of a Large Object.
This mode indicates we want to write to an object.
This mode indicates we want to read an object.
This mode is the default. It indicates we want read and write access to a large object.
public LargeObject open(int oid) throws SQLException
This opens an existing large object, based on its OID. This method assumes that READ and WRITE access is required (the default).
public LargeObject open(int oid,
int mode) throws SQLException
This opens an existing large object, based on its OID, and allows setting the access mode.
public int create() throws SQLException
This creates a large object, returning its OID. It defaults to READWRITE for the new object's attributes.
public int create(int mode) throws SQLException
This creates a large object, returning its OID, and sets the access mode.
public void delete(int oid) throws SQLException
This deletes a large object.
public void unlink(int oid) throws SQLException
This deletes a large object. It is identical to the delete method, and is supplied as the C API uses "unlink".
PostgreSQL is not a normal SQL database. It is more extensible than most other databases, and does support object oriented features that are unique to it.
One of the consequences of this, is that you can have one table refer to a row in another table. For example:
test=> create table users (username name,fullname text);
CREATE
test=> create table server (servername name,adminuser users);
CREATE
test=> insert into users values ('peter','Peter Mount');
INSERT 2610132 1
test=> insert into server values ('maidast',2610132::users);
INSERT 2610133 1
test=> select * from users;
username|fullname
--------+--------------
peter |Peter Mount
(1 row)
test=> select * from server;
servername|adminuser
----------+---------
maidast | 2610132
(1 row)
Okay, the above example shows that we can use a table name as
a field, and the row's oid value is stored in that field.
What does this have to do with Java?
In Java, you can store an object to a Stream as long as it's class implements the java.io.Serializable interface. This process, known as Object Serialization, can be used to store complex objects into the database.
Now, under JDBC, you would have to use a Large Object to store them. However, you cannot perform queries on those objects.
What the org.postgresql.util.Serialize class does, is provide a means of storing an object as a table, and to retrieve that object from a table. In most cases, you would not need to access this class direct, but you would use the PreparedStatement.setObject() and ResultSet.getObject() methods. Those methods will check the objects class name against the table's in the database. If a match is found, it assumes that the object is a Serialized object, and retrieves it from that table. As it does so, if the object contains other serialized objects, then it recurses down the tree.
Sound's complicated? In fact, it's simpler than what I wrote - it's just difficult to explain.
The only time you would access this class, is to use the create() methods. These are not used by the driver, but issue one or more "create table" statements to the database, based on a Java Object or Class that you want to serialize.
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 org.postgresql.util.Serialize
java.lang.Object
|
+----org.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
or deserialize 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 org.postgresql.util package contains classes used by the internals of
the main driver, and the other extensions.
Class org.postgresql.util.PGmoney
java.lang.Object
|
+----org.postgresql.util.PGobject
|
+----org.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 overridden 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 org.postgresql.util.PGobject
java.lang.Object
|
+----org.postgresql.util.PGobject
public class PGobject extends Object implements Serializable,
Cloneable
This class is used to describe data types that are unknown by
JDBC
Standard.
A call to org.postgresql.Connection permits a class that extends this
class to be associated with a named type. This is how the
org.postgresql.geometric package operates.
ResultSet.getObject() will return this class for any type that is
not recognized on having it's own handler. Because of this, any
PostgreSQL data type is supported.
Constructors
public PGobject()
This is called by org.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
overridden.
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 overridden, 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 overridden 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 overridden to allow the object to be cloned
Overrides:
clone in class Object
public String toString()
This is defined here, so user code need not override it.
Returns:
the value of this object, in the syntax expected by
PostgreSQL
Overrides:
toString in class Object
Class org.postgresql.util.PGtokenizer
java.lang.Object
|
+----org.postgresql.util.PGtokenizer
public class PGtokenizer extends Object
This class is used to tokenize the text output of PostgreSQL.
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 tokenizer.
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 data types 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:
String without the < or >
public void removeAngle()
Removes < and > from the beginning and end of all tokens
Returns:
String without the < or >
Class org.postgresql.util.Serialize
This was documented earlier under Object Serialization.
Class org.postgresql.util.UnixCrypt
java.lang.Object
|
+----org.postgresql.util.UnixCrypt
public class UnixCrypt extends Object
This class provides us with the ability to encrypt passwords when
sent over the network stream
Contains static methods to encrypt and compare passwords with Unix
encrypted passwords.
See John Dumas's Java Crypt page for the original source.
http://www.zeh.com/local/jfd/crypt.html
Methods
public static final String crypt(String salt,
String original)
Encrypt a password given the clear-text password and a
"salt".
Parameters:
salt - A two-character string representing the salt
used
to iterate the encryption engine in lots of different
ways. If you are generating a new encryption then this
value should be randomized.
original - The password to be encrypted.
Returns:
A string consisting of the 2-character salt followed
by
the encrypted password.
public static final String crypt(String original)
Encrypt a password given the clear-text password. This method
generates a random salt using the 'java.util.Random' class.
Parameters:
original - The password to be encrypted.
Returns:
A string consisting of the 2-character salt followed
by
the encrypted password.
public static final boolean matches(String encryptedPassword,
String enteredPassword)
Check that enteredPassword encrypts to encryptedPassword.
Parameters:
encryptedPassword - The encryptedPassword. The first
two characters are assumed to be the salt. This string would be the
same as one found in a Unix /etc/passwd file.
enteredPassword - The password as entered by the user
(or otherwise acquired).
Returns:
true if the password should be considered correct.