JDBC and Java Access to DBMS University of

JDBC and Java Access to DBMS University of

JDBC and Java Access to DBMS University of California, Berkeley School of Information IS 257: Database Management IS 257 Fall 2006 2006.11.02 SLIDE 1 Lecture Outline Review: Object-Relational DBMS OR features in Oracle OR features in PostgreSQL Extending OR databases (examples from PostgreSQL) Java and JDBC

IS 257 Fall 2006 2006.11.02 SLIDE 2 Lecture Outline Object-Relational DBMS OR features in Oracle OR features in PostgreSQL Extending OR databases (examples from PostgreSQL) Java and JDBC IS 257 Fall 2006 2006.11.02 SLIDE 3 Object Relational Data Model Class, instance, attribute, method, and

integrity constraints OID per instance Encapsulation Multiple inheritance hierarchy of classes Class references via OID object references Set-Valued attributes Abstract Data Types IS 257 Fall 2006 2006.11.02 SLIDE 4 Object Relational Extended SQL (Illustra) CREATE TABLE tablename {OF TYPE Typename}|{OF NEW TYPE typename} (attr1 type1, attr2 type2,,attrn typen) {UNDER parent_table_name}; CREATE TYPE typename (attribute_name

type_desc, attribute2 type2, , attrn typen); CREATE FUNCTION functionname (type_name, type_name) RETURNS type_name AS sql_statement IS 257 Fall 2006 2006.11.02 SLIDE 5 Object-Relational SQL in ORACLE CREATE (OR REPLACE) TYPE typename AS OBJECT (attr_name, attr_type, ); CREATE TABLE OF typename; IS 257 Fall 2006 2006.11.02 SLIDE 6

Example CREATE TYPE ANIMAL_TY AS OBJECT (Breed VARCHAR2(25), Name VARCHAR2(25), Birthdate DATE); Creates a new type CREATE TABLE Animal of Animal_ty; Creates Object Table IS 257 Fall 2006 2006.11.02 SLIDE 7 Constructor Functions INSERT INTO Animal values (ANIMAL_TY(Mule, Frances, TO_DATE(01-APR-1997, DD-MMYYYY))); Insert a new ANIMAL_TY object into the table

IS 257 Fall 2006 2006.11.02 SLIDE 8 PostgreSQL Classes The fundamental notion in Postgres is that of a class, which is a named collection of object instances. Each instance has the same collection of named attributes, and each attribute is of a specific type. Furthermore, each instance has a permanent object identifier (OID) that is unique throughout the installation. Because SQL syntax refers to tables, we will use the terms table and class interchangeably. Likewise, an SQL row is an instance and SQL columns are attributes. IS 257 Fall 2006 2006.11.02 SLIDE 9

Creating a Class You can create a new class by specifying the class name, along with all attribute names and their types: CREATE TABLE weather ( city varchar(80), temp_lo int, -- low temperature temp_hi int, -- high temperature prcp real, -- precipitation date date

); IS 257 Fall 2006 2006.11.02 SLIDE 10 PostgreSQL Postgres can be customized with an arbitrary number of user-defined data types. Consequently, type names are not syntactical keywords, except where required to support special cases in the SQL92 standard. So far, the Postgres CREATE command looks exactly like the command used to create a table in a traditional relational system. However, we will presently see that classes have properties that are extensions of the relational model. IS 257 Fall 2006

2006.11.02 SLIDE 11 Inheritance CREATE TABLE cities ( name text, population float, altitude int -- (in ft) ); CREATE TABLE capitals ( state char(2) ) INHERITS (cities); IS 257 Fall 2006 2006.11.02 SLIDE 12

Inheritance In Postgres, a class can inherit from zero or more other classes. A query can reference either all instances of a class or all instances of a class plus all of its descendants IS 257 Fall 2006 2006.11.02 SLIDE 13 Non-Atomic Values - Arrays The preceding SQL command will create a class named SAL_EMP with a text string (name), a one-dimensional array of int4 (pay_by_quarter), which represents the employee's salary by quarter and a two-dimensional array of text

(schedule), which represents the employee's weekly schedule Now we do some INSERTSs; note that when appending to an array, we enclose the values within braces and separate them by commas. IS 257 Fall 2006 2006.11.02 SLIDE 14 PostgreSQL Extensibility Postgres is extensible because its operation is catalogdriven RDBMS store information about databases, tables, columns, etc., in what are commonly known as system catalogs. (Some systems call this the data dictionary). One key difference between Postgres and standard RDBMS is that Postgres stores much more information in its catalogs

not only information about tables and columns, but also information about its types, functions, access methods, etc. These classes can be modified by the user, and since Postgres bases its internal operation on these classes, this means that Postgres can be extended by users By comparison, conventional database systems can only be extended by changing hardcoded procedures within the DBMS or by loading modules specially-written by the DBMS vendor. IS 257 Fall 2006 2006.11.02 SLIDE 15 Lecture Outline Review Object-Relational DBMS OR features in Oracle OR features in PostgreSQL Extending OR databases (examples from

PostgreSQL) Java and JDBC IS 257 Fall 2006 2006.11.02 SLIDE 16 Java and JDBC Java is probably the high-level language used in most software development today one of the earliest enterprise additions to Java was JDBC JDBC is an API that provides a mid-level access to DBMS from Java applications Intended to be an open cross-platform standard for database access in Java Similar in intent to Microsofts ODBC IS 257 Fall 2006

2006.11.02 SLIDE 17 JDBC Architecture The goal of JDBC is to be a generic SQL database access framework that works for any database system with no changes to the interface code Java Applications JDBC API JDBC Driver Manager IS 257 Fall 2006 Driver Driver Driver

Oracle MySQL Postgres 2006.11.02 SLIDE 18 JDBC Provides a standard set of interfaces for any DBMS with a JDBC driver using SQL to specify the databases operations. Resultset Resultset Resultset Statement

PreparedStatement CallableStatement Application Connection DriverManager Oracle Driver ODBC Driver Postgres Driver Oracle DB ODBC DB

Postgres DB IS 257 Fall 2006 2006.11.02 SLIDE 19 JDBC Simple Java Implementation import java.sql.*; import oracle.jdbc.*; public class JDBCSample { public static void main(java.lang.String[] args) { try { // this is where the driver is loaded //Class.forName("jdbc.oracle.thin"); DriverManager.registerDriver(new OracleDriver()); } catch (SQLException e) { System.out.println("Unable to load driver Class");

return; } IS 257 Fall 2006 2006.11.02 SLIDE 20 JDBC Simple Java Impl. try { //All DB access is within the try/catch block... // make a connection to ORACLE on Dream Connection con = DriverManager.getConnection( "jdbc:oracle:thin:@dream.sims.berkeley.edu:1521:dev", mylogin", myoraclePW"); // Do an SQL statement... Statement stmt = con.createStatement(); ResultSet rs = stmt.executeQuery("SELECT NAME FROM DIVECUST"); IS 257 Fall 2006

2006.11.02 SLIDE 21 JDBC Simple Java Impl. // show the Results... while(rs.next()) { System.out.println(rs.getString("NAME")); } // Release the database resources... rs.close(); stmt.close(); con.close(); } catch (SQLException se) { // inform user of errors... System.out.println("SQL Exception: " + se.getMessage()); se.printStackTrace(System.out); } } }

IS 257 Fall 2006 2006.11.02 SLIDE 22 JDBC Once a connection has been made you can create three different types of statement objects Statement The basic SQL statement as in the example PreparedStatement A pre-compiled SQL statement CallableStatement Permits access to stored procedures in the Database IS 257 Fall 2006

2006.11.02 SLIDE 23 JDBC Resultset methods Next() to loop through rows in the resultset To access the attributes of each row you need to know its type, or you can use the generic getObject() which wraps the attribute as an object IS 257 Fall 2006 2006.11.02 SLIDE 24 JDBC GetXXX() methods SQL data type CHAR VARCHAR LONGVARCHAR NUMERIC

Java Type String String String Java.math. BigDecimal DECIMAL Java.math. GetBigDecimal() BigDecimal BIT TINYINT Boolean Byte

IS 257 Fall 2006 GetXXX() getString() getString() getString() GetBigDecimal() getBoolean() getByte() 2006.11.02 SLIDE 25 JDBC GetXXX() Methods SQL data type SMALLINT INTEGER BIGINT REAL FLOAT

DOUBLE BINARY VARBINARY LONGVARBINARY IS 257 Fall 2006 Java Type Integer (short) Integer Long Float Double Double Byte[] Byte[] Byte[] GetXXX() getShort()

getInt() getLong() getFloat() getDouble() getDouble() getBytes() getBytes() getBytes() 2006.11.02 SLIDE 26 JDBC GetXXX() Methods SQL data type Java Type DATE TIME TIMESTAMP

java.sql.Date getDate() java.sql.Time getTime() Java.sql.Timestamp getTimeStamp() IS 257 Fall 2006 GetXXX() 2006.11.02 SLIDE 27 Large Object Handling Large binary databytes can be read from a resultset as streams using: getAsciiStream() getBinaryStream() getUnicodeStream()

ResultSet rs = stmt.executeQuery(SELECT IMAGE FROM PICTURES WHERE PID = 1223)); if (rs.next()) { BufferedInputStream gifData = new BufferedInputSteam( rs.getBinaryStream(IMAGE)); byte[] buf = new byte[4*1024]; // 4K buffer int len; while ((len = gifData.read(buf,0,buf.length)) != -1) { out.write(buf, 0, len); } 2006.11.02 SLIDE 28 } IS 257 Fall 2006 JDBC Metadata There are also methods to access the metadata associated with a resultSet ResultSetMetaData rsmd = rs.getMetaData(); Metadata methods include

getColumnCount(); getColumnLabel(col); getColumnTypeName(col) IS 257 Fall 2006 2006.11.02 SLIDE 29 JDBC access to MySQL The basic JDBC interface is the same, the only differences are in how the drivers are loaded public class JDBCTestMysql { public static void main(java.lang.String[] args) { try { // this is where the driver is loaded Class.forName("com.mysql.jdbc.Driver").newInstance(); } catch (InstantiationException i) {

System.out.println("Unable to load driver Class"); return; } catch (ClassNotFoundException e) { System.out.println("Unable to load driver Class"); IS 257 Fall 2006 2006.11.02 SLIDE 30 JDBC for MySQL try { //All DB access is within the try/catch block... // make a connection to MySQL on Dream Connection con = DriverManager.getConnection( "jdbc:mysql://dream.sims.berkeley.edu/ (this is really one line) MyDatabase?user=MyLogin&password=MySQLPW"); // Do an SQL statement... Statement stmt = con.createStatement();

ResultSet rs = stmt.executeQuery("SELECT NAME FROM DIVECUST"); Otherwise everything is the same as in the Oracle example For connecting to the machine you are running the program on, you can use localhost instead of the machine name IS 257 Fall 2006 2006.11.02 SLIDE 31

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