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important step towards making the driver compliant, and means that for some Java applications and servlets, only a single database connection is needed, so in a sence this is a nice little show stopper for 6.4 (and should still be backward compatible to 6.3.2). Peter |
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README_6.3 |
This is a simple readme describing how to compile and use the jdbc driver. This isn't a guide on how to use JDBC - for that refer to Javasoft's web site: http://www.javasoft.com or the JDBC mailing list: jdbc@java.blackdown.org http://www.blackdown.org For problems with this driver, then refer to the postgres-interfaces email list: http://www.postgresql.org By the time V6.3 is released, full documentation will be on the web, and in the distribution. --------------------------------------------------------------------------- COMPILING To compile the driver, simply use make in the src/interfaces/jdbc directory. This will compile the driver, and build a .jar file (Java ARchive). REMEMBER: once you have compiled the driver, it will work on ALL platforms that support the JDK 1.1 api or later. That means you don't have to compile it on every platform. Believe me, I still hear from people who ask me "I've compiled it ok under Solaris, but it won't compile under Linux" - there's no difference. PS: When you run make, don't worry if you see just one or two calls to javac. If, while compiling a class, javac needs another class that's not compiled, it will compile it automatically. This reduces the numer of calls to javac that make has to do. Possible problems You may see a message similar to: postgresql/Driver.java:87: interface java.sql.Connection is an interface. It can't be instantiated. return new Connection (host(), port(), props, database(), url, this); This is caused by not having the current directory in your CLASSPATH. Under Linux/Solaris, unset the CLASSPATH environment variable, and rerun make. --------------------------------------------------------------------------- INSTALLING THE DRIVER To install the driver, the .class files have to be in the classpath. This can be done in two ways: 1: create a directory "postgresql" (and it must be called this) in the current directory (or a directory in the class path), and copy all .class files into it. 2: copy the postgres.jar file into a directory, and add it to the classpath. ie: under LINUX/SOLARIS (the example here is my linux box): export CLASSPATH=.:/usr/local/lib/postgresql.jar:/usr/local/jdk1.1.1/lib/classes.zip note: in java, .zip and .jar files hold collections of classes. --------------------------------------------------------------------------- USING THE DRIVER To use the driver, you must introduce it to JDBC. Again, there's two ways of doing this: 1: Hardcoded. This method hardcodes your driver into your application/applet. You introduce the driver using the following snippet of code: try { Class.forName("postgresql.Driver"); } catch(Exception e) { // your error handling code goes here } Remember, this method restricts your code to just the postgresql database. 2: Parameters This method specifies the driver from the command line. When running the application, you specify the driver using the option: -Djdbc.drivers=postgresql.Driver eg: This is an example of running one of my other projects with the driver: java -Djdbc.drivers=postgresql.Driver finder.finder note: This method only works with Applications (not for Applets). However, the application is not tied to one driver, so if you needed to switch databases (why I don't know ;-) ), you don't need to recompile the application (as long as you havent hardcoded the url's). --------------------------------------------------------------------------- JDBC URL syntax The driver recognises JDBC URL's of the form: jdbc:postgresql:database jdbc:postgresql://host/database jdbc:postgresql://host:port/database Also, you can supply both username and passwords as arguments, by appending them to the URL. eg: jdbc:postgresql:database?user=me jdbc:postgresql:database?user=me&password=mypass By default, the driver doesn't use password authentication. You can enable this by adding the argument auth. ie: jdbc:postgresql:database?user=me&password=mypass&auth=password or if passing the user & password directly via DriverManager.getConnection(): jdbc:postgresql:database?auth=password PS: Password authentication is enabled if the value of auth starts with 'p'. It is case insensitive. As of postgresql 6.3, Ident (RFC 1413) authentication is also supported. Simply use auth=ident in the url. Also, as of 6.3, a system property of postgresql.auth is supported. This defines the default authentication to use. The auth property overides this. --------------------------------------------------------------------------- That's the basics related to this driver. You'll need to read the JDBC Docs on how to use it. POSTGRESQL SPECIFICS -------------------- Date datatype: The driver now supports US and European date styles (although it is currently limited to postgres format). Basically the US like to format their dates as mm-dd-yyyy, while in Europe, we like to use dd-mm-yyyy. Postgres supports this by the DateStyle variable. From psql, you can issue "set datestyle='european';" to set european style, and "set datestyle='us';" to set the US format. You can see what the current value for this with "show datestyle;". The driver now issues the "show datestyle;" query when it first connects, so any call to ResultSet.getDate() how returns the correct date. One caveat though: if you change the datestyle from within JDBC, you must also issue the "show datestyle" query. Without this, the driver will not know of the change. ie: Statement s = db.createStatement(); ... s.executeUpdate("set datestyle='european'"); s.executeUpdate("show datestyle"); .. s.close(); ------------------ JDBC supports database specific data types using the getObject() call. The following types have their own Java equivalents supplied by the driver: box, circle, lseg, path, point, polygon When using the getObject() method on a resultset, it returns a PG_Object, which holds the postgres type, and its value. This object also supports methods to retrive these types. Eg: column 3 contains a point, and rs is the ResultSet: PG_Object o = (PG_Object)rs.getObject(3); PGpoint p = o.getPoint(); System.out.println("point returned x="+p.x+", y="+p.y); Also, when using these classes, their toString() methods return the correct syntax for writing these to the database. --------------------------------------------------------------------------- Peter T Mount, January 11 1998 home email: pmount@maidast.demon.co.uk http://www.demon.co.uk/finder work email: peter@maidstone.gov.uk http://www.maidstone.gov.uk Adrian Hall email: adrian@hottub.org