JDBC connects to the database

The main steps for JDBC to connect to the database are as follows:

1. Load the JDBC driver

Class.forName ("com.mysql.jdbc.Driver")

After loading successfully, an instance of the Driver class is registered with the DriverManager class.

2. Provide URL to connect to JDBC

URL=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=gbk

UseUnicode=true&characterEncoding=gbk sets database encoding

3. Create a database connection

To connect to a database, you need to request a java.sql.DriverManager and get a Connection object, which represents a connection to a database.

String username= "root"; String password= "123456"; Connection conn=DriverManager.getConnection (URL,username,password)

4. Create a statement

To execute a SQL statement, you must obtain a java.sql.Statement instance. Common Statement instances are

(1) execute static SQL statements, usually through Statement instances

Statement st=conn.createStatement ()

(2) execute dynamic SQL statements, usually through PreparedStatement instances

String sql= "select * from tablename"; PreparedStatement ps=conn.perpareStatement (sql)

5. Execute the SQL statement

The Statement interface provides three ways to execute SQL statements: executeQuery,executeUpdate,execute

String sql= "select * from test"; String sql2= "insert into book" ("bookName", "price", "author"publish") values ("Java Technology", 99.999," Jhon "," Tsinghua University Press ")

① executeQuery (String sql): executes a query database statement that returns a result set ResultSet object

ResultSet rs=st.executeQuery (sql)

② executeUpdate (String sql): executes INSERT,UPDATE or DELETE statements and SQL DDL statements

Int rows=st.executeUpdate (sql2)

③ execute (String sql): used to execute statements that return multiple result sets, multiple update techniques, or combinations.

Boolean flag=st.execute (String sql)

6. Processing result

(1) the number of records affected by this operation is returned by performing the update.

(2) the result returned by executing the query is a ResultSet object.

While (rs.next ()) {string author=rs.getString (3); / / from left to right, index starts at 1}

7. Close the JDBC object

Close the recordset, close the declaration, and close the connection object.

If (rsgiving null) {rs.close ();} if (stalled null) {st.close ();} if (connate null) {conn.close;}