JDBC-上传和回滚例子
以下的例子将会用到之前提到的commit和rollback。
示例代码基于之前设置的环境和数据库编写。
复制粘贴代码到JDBCExample.java,编译运行如下:
编译上述代码:
当你运行JDBCExample的时候,产生如下输出:
示例代码基于之前设置的环境和数据库编写。
复制粘贴代码到JDBCExample.java,编译运行如下:
//STEP 1. Import required packages import java.sql.*; public class JDBCExample { // JDBC driver name and database URL static final String JDBC_DRIVER = "com.mysql.jdbc.Driver"; static final String DB_URL = "jdbc:mysql://localhost/EMP"; // Database credentials static final String USER = "username"; static final String PASS = "password"; public static void main(String[] args) { Connection conn = null; Statement stmt = null; try{ //STEP 2: Register JDBC driver Class.forName("com.mysql.jdbc.Driver"); //STEP 3: Open a connection System.out.println("Connecting to database..."); conn = DriverManager.getConnection(DB_URL,USER,PASS); //STEP 4: Set auto commit as false. conn.setAutoCommit(false); //STEP 5: Execute a query to create statment with // required arguments for RS example. System.out.println("Creating statement..."); stmt = conn.createStatement( ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE); //STEP 6: INSERT a row into Employees table System.out.println("Inserting one row...."); String SQL = "INSERT INTO Employees " + "VALUES (106, 20, 'Rita', 'Tez')"; stmt.executeUpdate(SQL); //STEP 7: INSERT one more row into Employees table SQL = "INSERT INTO Employees " + "VALUES (107, 22, 'Sita', 'Singh')"; stmt.executeUpdate(SQL); //STEP 8: Commit data here. System.out.println("Commiting data here...."); conn.commit(); //STEP 9: Now list all the available records. String sql = "SELECT id, first, last, age FROM Employees"; ResultSet rs = stmt.executeQuery(sql); System.out.println("List result set for reference...."); printRs(rs); //STEP 10: Clean-up environment rs.close(); stmt.close(); conn.close(); }catch(SQLException se){ //Handle errors for JDBC se.printStackTrace(); // If there is an error then rollback the changes. System.out.println("Rolling back data here...."); try{ if(conn!=null) conn.rollback(); }catch(SQLException se2){ se2.printStackTrace(); }//end try }catch(Exception e){ //Handle errors for Class.forName e.printStackTrace(); }finally{ //finally block used to close resources try{ if(stmt!=null) stmt.close(); }catch(SQLException se2){ }// nothing we can do try{ if(conn!=null) conn.close(); }catch(SQLException se){ se.printStackTrace(); }//end finally try }//end try System.out.println("Goodbye!"); }//end main public static void printRs(ResultSet rs) throws SQLException{ //Ensure we start with first row rs.beforeFirst(); 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); } System.out.println(); }//end printRs() }//end JDBCExample
编译上述代码:
C:>javac JDBCExample.java C:>
当你运行JDBCExample的时候,产生如下输出:
C:>java JDBCExample Connecting to database... Creating statement... Inserting one row.... Commiting data here.... List result set for reference.... ID: 100, Age: 18, First: Zara, Last: Ali ID: 101, Age: 25, First: Mahnaz, Last: Fatma ID: 102, Age: 30, First: Zaid, Last: Khan ID: 103, Age: 28, First: Sumit, Last: Mittal ID: 106, Age: 20, First: Rita, Last: Tez ID: 107, Age: 22, First: Sita, Last: Singh Goodbye! C:>