Create a program that connects the database with JDBC, which contains 7 steps:
1. Load JDBC Driver：
Before you connect to a database, you first load the drive to the JVM (Java Virtual Machine) of the database you want to connect to.
This is implemented by the static method forname (String className) of the Java.lang.Class class.
For example:
Copy Code code as follows:
try{
Load MySQL driver class
Class.forName ("Com.mysql.jdbc.Driver");
}catch (ClassNotFoundException e) {
System.out.println ("Driver class not found, load driver failed!") ");
E.printstacktrace ();
}
After a successful load, an instance of the driver class is registered to the DriverManager class.
2. Provide the URL of the JDBC connection
• The connection URL defines the protocol, child Protocol, and data source identity when connecting to a database.
• Writing form: Protocol: Sub-Protocol: Data source identification
Protocol: Always start with JDBC in JDBC
Sub-Protocol: The driver for the bridge connection or the name of the database management system.
Data source ID: Tag to locate the address and connection port of the database source.
For example: (MySQL's connection URL)
Jdbc:mysql:
LOCALHOST:3306/TEST?USEUNICODE=TRUE&CHARACTERENCODING=GBK;
Useunicode=true: Indicates the use of the Unicode character set. If Characterencoding is set to
gb2312 or GBK, this argument must be set to true. CHARACTERENCODING=GBK: Character encoding method.
3, create the connection of the database
• To connect to the database, you need to request and get the connection object to the Java.sql.DriverManager.
This object represents a connection to a database.
• Use DriverManager's getconnectin (string URL, string username,
The String password method passes in the path of the specified database to which you want to connect, the user name of the database, and
Password to obtain.
For example:
Copy Code code as follows:
Connect to MySQL database, username and password are root
String url = "Jdbc:mysql://localhost:3306/test";
String username = "root";
String password = "root";
try{
Connection con =
Drivermanager.getconnection (URL, username, password);
}catch (SQLException se) {
SYSTEM.OUT.PRINTLN ("Database connection failed!") ");
Se.printstacktrace ();
}
4. Create a statement
• To execute the SQL statement, you must obtain the Java.sql.Statement instance, which is divided into the following 3 statement instances
Types of:
1, execute static SQL statement. Typically implemented through statement instances.
2, execute dynamic SQL statements. Typically implemented through PreparedStatement instances.
3, execute the database stored procedure. Typically implemented through CallableStatement instances.
Specific ways to achieve:
Copy Code code as follows:
Statement stmt = Con.createstatement ();
PreparedStatement pstmt = con.preparestatement (sql);
CallableStatement cstmt =
Con.preparecall ("{Call Demosp (?,?)}");
5. Execute SQL statement
The statement interface provides three ways to execute SQL statements: ExecuteQuery, executeupdate
and execute
1, ResultSet executequery (String sqlstring): Executing the SQL statement of the query database
, returns a result set (ResultSet) object.
2, int executeupdate (String sqlstring): Used to perform INSERT, UPDATE, or
Delete statements and SQL DDL statements, such as CREATE table and drop table
3. Execute (sqlstring): Used to perform returns of multiple result sets, multiple update counts, or combination of both
Statement.
Specific code to implement:
Copy Code code as follows:
ResultSet rs = stmt.executequery ("SELECT * from ...");
int rows = Stmt.executeupdate ("INSERT into ...");
Boolean flag = Stmt.execute (String sql);
6, processing results
Two cases:
1, the execution of the update returns the number of records affected by this operation.
2. The result returned by the execution query is a ResultSet object.
resultset contains all the rows that conform to the conditions in the SQL statement, and it provides a set of get methods that provide the
Access to data in the row.
• Get data using the access method of the result set (ResultSet) object:
Copy Code code as follows:
while (Rs.next ()) {
String name = rs.getstring ("name");
String pass = rs.getstring (1); This method is more efficient
}
(columns are numbered from left to right, and starting from column 1)
7. Close JDBC Object
After the operation is complete, all JDBC objects used are closed to release the JDBC resource, turn off the order harmony
The order of the Ming is the opposite:
1, close the recordset
2. Close the statement
3, close the Connection object
Copy Code code as follows:
if (Rs!= null) {//close Recordset
try{
Rs.close ();
}catch (SQLException e) {
E.printstacktrace ();
}
}
if (stmt!= null) {//Close declaration
try{
Stmt.close ();
}catch (SQLException e) {
E.printstacktrace ();
}
}
IF (conn!= null) {//Close Connection object
try{
Conn.close ();
}catch (SQLException e) {
E.printstacktrace ();
}
}
