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[JDBC] quick start tutorial
2022-07-06 07:09:00 【Vortex programming, a blockbuster】
1. What is? JDBC?
JDBC API It's a Java API, You can access any type of table column data , In particular, data stored in relational databases .JDBC representative Java Database connection .
JDBC The library contains API Usually used with databases :
- Connect to database
- establish SQL or MySQL sentence
- Execute... In the database SQL or MySQL Inquire about
- View and modify data records in the database
2.JDBC Environment configuration
- JAVA(JDK) install
- Installation of database system ( Such as MySQL,SQL Server Installation )
3. establish JDBC Applications
Build a JDBC Applications , This tutorial uses java Connect SQL Server For example , It is carried out in six steps :
1. Import package
Include in the program what is needed for database programming JDBC class . Most of the time , Use import java.sql.*
That's enough
2. register JDBC The driver
Initialize the driver , Open communication with the database .
Class.forName("com.mysql.cj.jdbc.Driver");
3. Open the link
Use DriverManager.getConnection()
Method to create a Connection
object ,
String user="sa";
String pwd="123456";
System.out.println(" Connect to database ...");
Connection con=DriverManager.getConnection(url,user,pwd);
4. Execute a query
Use one Statement
Type or PreparedStatement
The object of , And submit a SQL Statement to the database to execute the query :
System.out.println(" establish statement...");
Statement sm=con.createStatement();
String sql="SELECT * FROM Students";
ResultSet rs=sm.executeQuery(sql);
If you want to execute a SQL sentence :UPDATE,INSERT,DELETE sentence , as follows :
sm=con.createStatement();
String sql="DELETE FROM Students";
ResultSet rs=sm.executeUpdate(sql);
5. Extract data from the result set
This step demonstrates how to get the data of query results from the database . You can use the appropriate ResultSet.getXXX()
Method to retrieve the data, and the results are as follows :
//STEP 5: Extract data from result set
while(rs.next()){
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
//Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}
6. Clean up environmental resources
In the use of JDBC After interacting with the data in the database , All database resources should be explicitly shut down to reduce the waste of resources , Depend on JVM The garbage collection of is as follows :
//STEP 6: Clean-up environment
rs.close();
stmt.close();
con.close();
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