JDBC interfeisa izmantošana SQL komandu realizēšanai

SQL Java JDBC DB

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JDBC API komponentes

1. DriverManager: This class manages a list of database drivers. Matches connection requests from the java application with the proper database driver using communication subprotocol. The first driver that recognizes a certain subprotocol under JDBC will be used to establish a database Connection.

2. Driver: This interface handles the communications with the database server. You will interact directly with Driver objects very rarely. Instead, you use DriverManager objects, which manages objects of this type. It also abstracts the details associated with working with Driver objects.

3. Connection : This interface with all methods for contacting a database. The connection object represents communication context, i.e., all communication with database is through connection object only.

4. Statement : You use objects created from this interface to submit the SQL statements to the database. Some derived interfaces accept parameters in addition to executing stored procedures.

5. ResultSet: These objects hold data retrieved from a database after you execute an SQL query using Statement objects. It acts as an iterator to allow you to move through its data.

6. SQLException: This class handles any errors that occur in a database application.

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JDBC API programmu paketes

1. java.sql (provides the API for accessing and processing data stored in a data source using the Java programming language. This package provides the foundation and most commonly used objects such as Connection, ResultSet, Statement, and PreparedStatement.).

2. javax.sql (provides the API for server-side data source access and processing from the Java programming language. This package provides services for data objects DataSource and RowSet.).

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java.sql programmu paketes galvenās klases

1. java.sql.DriverManager: The major task of the DriverManager class is to access the JDBC drivers and create java.sql.Connection (database connection) objects.

2. java.sql.Connection: This interface represents a database connection. This is the key for accessing most of the database objects (such as tables, columns, and so on).

3. java.sql.Statement: The Connection object creates Statement objects. You can use the Statement object to execute SQL statements and queries, which produce ResultSet objects (the result of executing SQL statements and queries).

4. java.sql.PreparedStatement: The Connection object creates PreparedStatement (parameterized statement) objects. You can use the PreparedStatement object to execute SQL statements and queries, which produce ResultSet objects (the result of executing SQL statements and queries).

5. java.sql.CallableStatement: The Connection object creates CallableStatement (statements used to execute stored procedures) objects. You can use the PreparedStatement object to execute SQL statements and queries, which produce ResultSet objects (the result of executing SQL statements and queries).

6. java.sql.ResultSet: The result of a SQL query is returned via a ResultSet object (a table of data representing a database result set, which is usually generated by executing a statement that queries the database).

7. SQLException: This class is an exception class that provides information on a database access error or other errors.

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java.sql.DriverManager klase un JDBC draiveri

java.sql.DriverManager ir savienojumu veidošanas klase (savienojumu rūpnīca (connection factory)). Tā ir vienīgā klase, kura var izveidot savienojumus ar datu bāzi. Katrs savienojums ir java.sql.Connection objekts.

Driver Manager klase izmanto JDBC dzini (driver) lai izveidotu savienojumu. Katra datu bāzes sistēmas izstrādātāja firma (piemēram, Oracle, IBM, MS, Sybase) veic apgādi ar nepieciešamajiem dziņiem.

JDBC dzinis ir Java klase, kura realizē java.sql.Driver interfeisu. Tā saprot kā SQL vaicājumu vai DB glabājamās procedūras izsaukumu nodot datu bāzes sistēmai, lai tā to izpildītu. Dziņi tiek noformēti kā *.jar vai *.zip tipa faili. Dziņa instalēšana nozīmē viņa glabāšanas (atrašanās) vietas norādīšana operētājsistēmā (parametrs CLASSPATH):

CLASSPATH=c:\\oracle\oracle\10.1.0\jdbc\lib\ojdbc14.jar;%CLASSPATH%

Make sure following environment variables are set as described below:1) JAVA_HOME: This environment variable should point to the directory where you installed the JDK, e.g. C:\Program Files\Java\jdk1.5.0D:\oracle\product\10.2.0\db_1\jdk

2) CLASSPATH: This environment variable should have appropriate paths set, e.g. C:\Program Files\Java\jdk1.5.0_20\jre\libD:\oracle\product\10.2.0\db_1\jdk\jre\lib

3) PATH: This environment variable should point to appropriate JRE bin, e.g. C:\Program Files\Java\jre1.5.0_20\binD:\oracle\product\10.2.0\db_1\jdk\jre\bin

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JDBC interfeisa izmantošanas pamatdarbības

1. JDBC interfeisa programmu pakešu imports (nepieciešamo JDBC Java klašu piesaiste).

2. JDBC dziņa (draivera) reģistrācija. Vēlamā draivera realizācija tiek ielādēta operatīvajā atmiņā, lai varētu izpildīt JDBC pieprasījumus (requests).

3. Datu bāzes URL norādīšana. Izmantojamās datu bāzes adreses norādīšana.

4. Lietojuma un datu bāzes savienojuma objekta Connection izveidošana. DriverManager objekta getConnection() metodes izsaukums. Tas izveido savienojumu ar datu bāzi.

5. SQL komandas objekta (statement) izveidošana.

6. Vaicājuma izpilde un rezultāta ieguve (execute a query and return a

ResultSet object).

7. Iegūtā rezultāta apstrāde (process the ResultSet object).

8. Rezultāta un komandas objektu aizvēršana (close the ResultSet and

Statement objects).

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JDBC izmantošanas pamatshēma

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1. darbība. JDBC programmu pakešu imports

import java.sql.* ; // JDBC bibliotēka.import oracle.jdbc.driver.* ; // Bibliotēka ar datu bāzes draiveriem.

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Lai savienotu Java lietojuma programmu ar datu bāzes sistēmu, tiek realizētas sekojošas darbības

1. Tiek veikta Oracle, Java un JDBC programmu ietvaru

iestatīšana.

2. Tiek veikts nepieciešamo JDBC klašu imports (JDBC un

Oracle).

3. Konkrētās datu bāzes sistēmas savienojuma nodrošināšanas

programmas (database driver) piesaiste un reģistrēšana.

4. Savienojuma objekta (connection object) izveidošana ar

savienojuma nodrošināšanas programmas palīdzību.

The java.sql.Connection object represents a single logical database connection. You use the Connection object for sending a set of SQL statements to the database server and managing the committing or aborting (rollback) of those SQL statements.

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2. darbība. JDBC draivera reģistrēšana un savienojuma objekta izveidošana.

First it needs to establish a connection with the data source you want to use. A data source can be a DBMS, a legacy file system, or some other source of data with a corresponding JDBC driver. Typically, a JDBC application connects to a target data source using one of two classes:1. DriverManager: This fully implemented class connects an application to a data source, which is specified by a database URL. When this class first attempts to establish a connection, it automatically loads any JDBC 4.0 drivers found within the class path. Note that your application must manually load any JDBC drivers prior to version 4.0.2. DataSource: This interface is preferred over DriverManager because it allows details about the underlying data source to be transparent to your application. A DataSource object's properties are set so that it represents a particular data source.

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JDBC Thin Client

The JDBC Thin client is a pure Java, Type IV driver. It is lightweight and easy to install. It provides high performance, comparable to the performance provided by the JDBC Oracle Call Interface (OCI) driver. The JDBC Thin driver is written entirely in Java, and therefore, it is platform-independent. Also, this driver does not require any additional Oracle software on the client-side.

The JDBC Thin driver communicates with the server using TTC, a protocol developed by Oracle to access data from Oracle Database. It can be used for application servers as well as for applets. The driver allows a direct connection to the database by providing an implementation of TCP/IP that implements Oracle Net and TTC on top of Java sockets. Both of these protocols are lightweight implementation versions of their counterparts on the server. The Oracle Net protocol runs over TCP/IP only.

The JDBC Thin driver can be used on both the client-side and the server-side. On the client-side, drivers can be used in Java applications or Java applets that run either on the client or in the middle tier of a three-tier configuration. On the server-side, this driver is used to access a remote Oracle Database instance or another session on the same database.

Additional Features Supported

The JDBC Thin driver supports all standard JDBC features. The JDBC Thin driver also provides support for the following additional features:

Support for Applets Default Support for Native XA

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2. darbība. JDBC draivera reģistrēšana un savienojuma objekta izveidošana. Klases DriverManager izmantošana

Datu bāzes draivera programmas reģistrācija ir process kurā draivera klase tiek ielādēta atmiņā, lai tā varētu realizēt JDBC interfeisu.

DriverManager.registerDriver(new oracle.jdbc.OracleDriver());static Connection conn = null;conn = DriverManager.getConnection("jdbc:oracle:thin:@dators:1521:BAZE", "system", "janis");

Driver DBdzinis = new oracle.jdbc.driver.OracleDriver();DriverManager.registerDriver(DBdzinis); static Connection conn = null;conn = DriverManager.getConnection("jdbc:oracle:thin:@dators:1521:BAZE", "system", "janis");

Connection conn = DriverManager.getConnection("jdbc:default:connection:");

Connection conn =DriverManager.defaultConnection();

Ja kļūda – SQLException;

However, the server-side internal JDBC driver runs within a default session and a default transaction context. As a result, you are already connected to the database, and all your SQL operations are part of the default transaction. You need not register the driver because it comes preregistered.

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2. darbība. JDBC draivera reģistrēšana un savienojuma objekta izveidošana. Oracle Call Interface (OCI) draivera izmantošana (klases forName lietošana)

Class.forName ("oracle.jdbc.OracleDriver");Connection conn = DriverManager.getConnection ("jdbc:oracle:oci8:@localhost", "system", "janis");

Bet var arī:

Class.forName ("oracle.jdbc.OracleDriver");Connection conn = DriverManager.getConnection ("jdbc:oracle:thin:@//localhost:1521/BAZE", "system", "janis"); Ja kļūda – ClassNotFoundException.

Oracle's JDBC Thin driver uses Java sockets to connect directly to Oracle. It provides its own TCP/IP version of Oracle's SQL*Net protocol. Because it is 100% Java, this driver is platform independent and can also run from a Web Browser (applets).

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2. darbība. Savienojuma ar datu bāzes sistēmu izveidošana.Oracle KPRB draiveris

Connection conn = (new oracle.jdbc.OracleDriver()).defaultConnection();

Oracle's JDBC KPRB driver is mainly used for writing Java stored procedures, triggers and database JSPs. It uses the default/ current database session and thus requires no additional database username, password or URL. Remember not to close the default Connection. Closing the default connection might throw an exception in future releases of Oracle.

jdbc:oracle:kprbjdbc:default:connectionjdbc:oracle:kprb:jdbc:default:connection:

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Pamatdarbības izmantojot JDBC draiverus

First it needs to establish a connection with the data source you want to use. A data source can be a DBMS, a legacy file system, or some other source of data with a corresponding JDBC driver. Typically, a JDBC application connects to a target data source using one of two classes:1. DriverManager: This fully implemented class connects an application to a data source, which is specified by a database URL. When this class first attempts to establish a connection, it automatically loads any JDBC 4.0 drivers found within the class path. Note that your application must manually load any JDBC drivers prior to version 4.0.2. DataSource: This interface is preferred over DriverManager because it allows details about the underlying data source to be transparent to your application. A DataSource object's properties are set so that it represents a particular data source.

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2. darbība. OracleDataSource klases izmantošana savienojuma veidošanai ar datu bāzes sistēmu

OracleDataSource ods = new OracleDataSource();ods.setURL("jdbc:oracle:kprb");Connection conn = ods.getConnection();

OracleDataSource ods = new OracleDataSource();ods.setURL("jdbc:default:connection");Connection conn = ods.getConnection();

ods = new OracleDataSource();ods.setURL("jdbc:oracle:thin:@//server.local:1521/prod");ods.setUser("scott"); ods.setPassword("tiger");

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2. darbība. Datu bāzes adreses (URL) norādīšana

Izmantojot DriverManager.getConnection() metodi var izmantot trīs variantus datu bāzes URL norādei:

getConnection(String url)getConnection(String url, Properties prop)getConnection(String url, String user, String password)

DBVS JDBC dziņa nosaukums URL formāts

MySQL com.mysql.jdbc.Driver jdbc:mysql://hostname/ databaseName

ORACLE oracle.jdbc.driver.OracleDriver

jdbc:oracle:thin:@hostname:port Number:databaseName

DB2 COM.ibm.db2.jdbc.net.DB2Driver

jdbc:db2:hostname:port Number/databaseName

Sybase com.sybase.jdbc.SybDriver jdbc:sybase:Tds:hostname: port Number/databaseName

A JDBC URL is the connect string used during database connection requests. It specifies the JDBC driver type, authentication information, the database instance, the host, the protocol, the port, service name, and so on. It contains either the complete authentication information or partial information plus indirections (i.e., aliases) to other mechanisms such as the TNSNAMES.ORA.The Oracle JDBC URL format is as follows:

jdbc:oracle:<drivertype>:[<username>/<password>]@<database_specifier>where:<drivertype> = “thin” | “oci” | “kprb”[<username>/<password>] = “<username>”/”<password>” | empty

jdbc:oracle:thin:@localhost:1521:orcl jdbc:oracle:thin:@localhost:1521/myservice - Rekomendētais jaunais pieraksta variants

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Savienojuma pārbaudes programmacreate or replace JAVA source named "Tests" asimport java.sql.*;import oracle.jdbc.pool.*;public class Tests {public static String Metode() throws ClassNotFoundException,      SQLException {// Tipiskie JNDI savienojuma parametriOracleDataSource ds = new OracleDataSource();ds.setDriverType("thin"); ds.setServerName("localhost"); ds.setPortNumber(1521); ds.setDatabaseName("BAZE"); // sidds.setUser("system"); ds.setPassword("Janis1946"); Connection conn = ds.getConnection(); Statement stmt = conn.createStatement(); ResultSet rset = stmt.executeQuery("select 'Savienojuma pārbaude' from dual"); if (rset.next()) System.out.println(rset.getString(1)); rset.close(); stmt.close();String m = "AAA";return m;}}

create or replace JAVA source named "Tests" asimport java.sql.*;import oracle.jdbc.*;public class Tests {public static String Metode() {String m = "AAA";return m;}}

create or replace function TESTS_1 return varchar2 as language JAVA name 'Tests.Metode() return java.lang.String';

set serveroutput on;call DBMS_JAVA.SET_OUTPUT(2000);

select TESTS_1 from DUAL;

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JDBC draivera versijas noteikšana(servera programma)

create or replace JAVA source named "JDBCVersija" asimport java.sql.*;import oracle.jdbc.*;import oracle.jdbc.pool.OracleDataSource;class JDBCVersija{ public static void main (String args[ ]) throws SQLException { OracleDataSource ods = new OracleDataSource(); ods.setURL("jdbc:oracle:thin:JAVA_L/janis@DATORS:1521:BAZE"); Connection conn = ods.getConnection(); // Create Oracle DatabaseMetaData object DatabaseMetaData meta = conn.getMetaData(); // gets driver info: System.out.println("JDBC driver version is " + meta.getDriverVersion()); } ;

create or replace procedure JDBCVERSIJAas language JAVA name 'JDBCVersija.main(java.lang.String[ ])';

SQL> SET SERVEROUTPUT ONSQL> CALL dbms_java.set_output(2000);SQL>call JDBCVERSIJA();JDBC driver version is 10.1.0.2.0

select OBJECT_NAME, OBJECT_TYPE, STATUSfrom USER_OBJECTS;OBJECT_NAME OBJECT_TYPE STATUS----------------------------------------------------------------------------JDBCVERSIJA PROCEDURE VALIDJDBCVersija JAVA CLASS VALIDJDBCVersija JAVA SOURCE VALID

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3. darbība. Priekšraksta (statement) jeb komandas objekta izveidošana. Statement klase

Statement klase. Lieto SQL komandām, kurām nav IN tipa parametru.

String sql = "DROP " + object_type + " " + object_name;Statement stmt = conn.createStatement();stmt.executeUpdate(sql);

String sql = "SELECT COUNT(*) FROM " + tabName;int rows = 0;Statement stmt = conn.createStatement();ResultSet rset = stmt.executeQuery(sql);while (rset.next()) {rows = rset.getInt(1);}

A ResultSet object contains SQL query results, that is, the rows that meet the search condition. You can use the next() method to move to the next row, which then becomes the current row. You can use the getXXX() methods to retrieve column values from the current row.

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3. darbība. Priekšraksta (statement) vai komandas objekta izveidošana. PreparedStatement klase

PreparedStatement klase. Lieto SQL komandām, kurām ir IN tipa parametri un kuras tiek izpildītas atkārtoti. Notiek pārkompilācijas.

String sql = "DELETE FROM dept WHERE deptno = ?";PreparedStatement pstmt = conn.prepareStatement(sql);pstmt.setInt(1, deptID);pstmt.executeUpdate();

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3. darbība. Priekšraksta (statement) vai komandas objekta izveidošana. CallableStatement klase

CallableStatement lieto datu bāzes serverī glabājamo funkciju un procedūru izsaukšanai. Var būt IN un OUT tipa parametri.

// parameterless stored procedureCallableStatement cstmt = conn.prepareCall("{CALL proc}");

// stored procedureCallableStatement cstmt = conn.prepareCall("{CALL proc(?,?)}");

// stored functionCallableStatement cstmt = conn.prepareCall("{? = CALL func(?,?)}");

Important Points. When developing JDBC applications that access stored procedures, you must consider the following:1) Each Oracle JVM session has a single implicit native connection to the Database session in which it exists. This connection is conceptual and is not a Java object. It is an inherent aspect of the session and cannot be opened or closed from within the JVM.2) The server-side internal JDBC driver runs within a default transaction context. You are already connected to the database, and all your SQL operations are part of the default transaction. Note that this transaction is a local transaction and not part of a global transaction, such as that implemented by Java Transaction API (JTA) or Java Transaction Service (JTS).3) Statements and result sets persist across calls and their finalizers do not release database cursors. To avoid running out of cursors, close all statements and result sets after you have finished using them. Alternatively, you can ask your DBA to raise the limit set by the initialization parameter, OPEN_CURSORS.4) The server-side internal JDBC driver does not support auto-commits. As a result, your application must explicitly commit or roll back database changes.5) You cannot connect to a remote database using the server-side internal JDBC driver. You can connect only to the server running your Java program. For server-to-server connections, use the server-side JDBC Thin driver. For client/server connections, use the client-side JDBC Thin or JDBC Oracle Call Interface (OCI) driver.6) Typically, you should not close the default connection instance because it is a single instance that can be stored in multiple places, and if you close the instance, each would become unusable. If it is closed, a later call to the OracleDriver.defaultConnection method gets a new, open instance. The OracleDataSource.getConnection method returns a new object every time you call it, but, it does not create a new database connection every time. They all utilize the same implicit native connection and share the same session state, in particular, the local transaction.

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4. darbība. SQL komandas izpilde: execute-Query(), executeUpdate(), execute()

ResultSet rezultats = komanda.executeQuery("select NOS from FIRMAS");

int rowcount = komanda.executeUpdate("create table FIRMAS (NUM number, NOS varchar2(20)");

int rowcount = komanda.executeUpdate(“delete from FIRMAS where NUM = 7");

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5. darbība. Iegūto rezultātu - ResultSet objekta apstrāde

while (rezultats.next()) {String nos = rezultats.getString("NOS");int num = rezultats.getInt("NUM");… }

NUMBER getInt()DATE getDate()VARCHAR2 getString()BLOB getBlob()CLOB getClob()ARRAY getArray()Structured type getObject()REF getRef()

6. darbība. Piesaistīto resursu atbrīvošana (aizvēršana)

rezultats.close();komanda.close();savienojums.close(); (Jāuzmanās !!!)