运用ThreadLocal解决jdbc事务管理

JdbcUtils.java

public class JdbcUtils {
    private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
    private static DataSource ds;
    
    static {
        ds = new ComboPooledDataSource();
    }
    
    public static DataSource getDataSource() {
        return ds;
    }
    
    // 当前线程绑定一个开启事务的连接
    // ThreadLocal是一个map集合 具有get() set() remove()方法 key是线程名称
    public static Connection getConnection() throws SQLException {
        Connection conn = tl.get();
        if (conn == null) {
            conn = ds.getConnection();
            tl.set(conn);            
        }
        return conn;
    }
    
    public static void startTransaction() {
        try {
            Connection conn = getConnection(); //调用
            if(conn != null) {
                conn.setAutoCommit(false);
            }
        } catch (Exception e) {
            throw new RuntimeException();
        }
    }
    
    public static void rollback() {
        try {
            Connection conn = getConnection(); //调用
            if(conn != null) {
                conn.rollback();
                conn.commit();
            }
        } catch (Exception e) {
            throw new RuntimeException();
        }
    }
    
    public static void commit() {
        try {
            Connection conn = getConnection(); //调用
            if(conn != null) {
                conn.commit();
            }
        } catch (Exception e) {
            throw new RuntimeException();
        }
    }
    
    public static void close() {
        try {
            Connection conn = getConnection(); //调用
            if(conn != null) {
                try {
                    conn.close();
                } finally {
                    tl.remove();
                }                
            }
        } catch (Exception e) {
            throw new RuntimeException();
        }
    }
}

AccountService.java

public class AccountService {
    
    // ThreadLocal 解决方案
    public void transfer(int sourceid,int destid,double money) throws SQLException {
        
        try {
            JdbcUtils.startTransaction();
            AccountDao dao = new AccountDao();
            
            Account a = dao.find(sourceid); //select
            Account b = dao.find(destid); //select
            
            a.setMoney(a.getMoney()-100);
            b.setMoney(b.getMoney()+100);
            
            dao.update(a); //update
            dao.update(b); //update

　　　　　　　JdbcUtils.commit();            
        } catch (Exception e) {
            JdbcUtils.rollback();
　　　　　　　throw new RuntimeException();
        } finally {
            JdbcUtils.close();
        }
        
}