以下是使用事務教學中描述的setSavepoint和回滾的程式碼範例。
此範例程式碼是基於前面章節中完成的環境和資料庫設定編寫的。
複製並將以下範例程式碼儲存到：JDBCSavepoint.java 中，編譯並執行如下 -
//STEP 1. Import required packages
// See more detail at /20/213/8320.html
import java.sql.*;
public class JDBCSavepoint {
// 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 = "root";
static final String PASS = "123456";
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 delete statment with
// required arguments for RS example.
System.out.println("Creating statement...");
stmt = conn.createStatement();
//STEP 6: 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 7: delete rows having ID grater than 104
// But save point before doing so.
Savepoint savepoint1 = conn.setSavepoint("ROWS_DELETED_1");
System.out.println("Deleting row....");
String SQL = "DELETE FROM Employees " +
"WHERE ID = 106";
stmt.executeUpdate(SQL);
// oops... we deleted too wrong employees!
//STEP 8: Rollback the changes afetr save point 2.
conn.rollback(savepoint1);
// STEP 9: delete rows having ID grater than 104
// But save point before doing so.
Savepoint savepoint2 = conn.setSavepoint("ROWS_DELETED_2");
System.out.println("Deleting row....");
SQL = "DELETE FROM Employees " +
"WHERE ID = 107";
stmt.executeUpdate(SQL);
//STEP 10: Now list all the available records.
sql = "SELECT id, first, last, age FROM Employees";
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
編譯並執行結果如下 -
F:\worksp\jdbc>javac -Djava.ext.dirs=F:\worksp\jdbc\libs JDBCSavepoint.java
F:\worksp\jdbc>java -Djava.ext.dirs=F:\worksp\jdbc\libs JDBCSavepoint
Connecting to database...
Thu Jun 01 02:35:49 CST 2017 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
Creating statement...
List result set for reference....
ID: 100, Age: 28, First: Max, Last: Su
ID: 101, Age: 25, First: Wei, Last: Wang
ID: 102, Age: 35, First: Xueyou, Last: Zhang
ID: 103, Age: 30, First: Jack, Last: Ma
ID: 106, Age: 28, First: Curry, Last: Stephen
ID: 107, Age: 32, First: Kobe, Last: Bryant
Deleting row....
Deleting row....
List result set for reference....
ID: 100, Age: 28, First: Max, Last: Su
ID: 101, Age: 25, First: Wei, Last: Wang
ID: 102, Age: 35, First: Xueyou, Last: Zhang
ID: 103, Age: 30, First: Jack, Last: Ma
ID: 106, Age: 28, First: Curry, Last: Stephen
Goodbye!
F:\worksp\jdbc>
可以看到，上面程式碼中只回滾到儲存點(ROWS_DELETED_1)，所以ID為106的這一行記錄沒有被刪除，而ID為107的記錄因為沒有設定回滾點，直接提交刪除了。