Java Database programming

1. Basic process of Java database operation
2, a few common important skills:
Scrollable, updated recordset
Batch Update
Transaction processing
Basic process of Java database operation: Get database connection-Execute SQL statement-Process Execution Result-free database connection
1. Get the database connection
1) Use DriverManager to fetch the database connection
Example:
String classname,url,uid,pwd;
ClassName = "Oracle.jdbc.driver.OracleDriver";
url = "JDBC:ORACLE:THIN:@127.0.0.1:1521:ORASVR;
UID = "System";
PWD = "Manager";
Class.forName (ClassName);
Connection cn = drivermanager.getconnection (URL,UID,PWD);
2) using Jndi (naming and directory services for Java)
Example
String Jndi = "jdbc/db";
Context CTX = (context) new InitialContext (). Lookup ("java:comp/env");
DataSource ds = (DataSource) ctx.lookup (JNDI);
Connection cn = Ds.getconnection ();
Used more in JSP
2. Execute SQL statements
1) Execute SQL statements with statement
String SQL;
Statement sm = cn.createstatement ();
Sm.executequery (SQL); Execute Data query statement (SELECT)
Sm.executeupdate (SQL); Execute Data UPDATE statement (delete, update, Inssert, DROP, etc.) Statement.close ();
2) Execute SQL statements with PreparedStatement
String SQL;
sql = "Inssert into user (Id,name) VALUES (?,?)";
PreparedStatement PS = cn.preparestatement (SQL);
Ps.setint (1,XXX);
Ps.setstring (2,XXX);
...
ResultSet rs = Ps.executequery (); Inquire
int c = Ps.executeupdate (); Update
3. Processing execution Results
A query statement that returns the recordset resultset.
UPDATE statement, which returns a number indicating the number of records affected by the update.
Methods of ResultSet:
1, Next (), moves the cursor back one line, or False if it returns true if it succeeds.
2, GETINT ("id") or getsting ("name"), returns the value of a field under the current cursor.
3, release the connection.
Cn.close ();
In general, close the resultset first, then close statement (or PreparedStatement), and finally close the connection
Scrollable, updated recordset
1. Create scrollable, updated statement
Statement sm = cn.createstatement (resultset.type_scroll_ensitive,resultset.concur_read_only);
The resultset obtained by the statement is a scrollable
2. Many parameters are specified when creating PreparedStatementJava Video TutorialsIt is recommended to use this preparedstatement, said to prevent SQL injection
Preparedstatemet PS = cn.preparestatement (sql,resultset.type_scroll_insensitive,resultset.concur_read_only);
Resultset.absolute (9000);
Batch Update

1=2= cn.preparedstatement (SQL); {Ps.setxxx (1

A PreparedStatement, you can put an SQL statement, transform parameters to execute multiple times, one update.
Handling of transactions
1. Turn off automatic submission of connection
Cn.setautocommit (FALSE);
2. Execute a series of SQL statements
Important: Before executing each new SQL statement, the last statement (or Preparedstatemet) that executed the SQL statement must first close
Statement SM;
SM = cn.createstatement (Inssert into user ...);
Sm.executeupdate ();
Sm.close ();
SM = cn.createstatement ("Inssert into Corp ...);
Sm.executeupdate ();
Sm.close ();
3. Submit
Cn.commit ();
4, if an exception occurs, then rollback
Cn.rollback ();

Java Database programming