82_Java_JDBC3_DAO_事物

DAO

1 通用DAO

public abstract class BaseDAO {
    // 通用增删改
    public int update(Connection conn, String sql, Object ...args)  {
        PreparedStatement ps  = null;
        try {
            ps = conn.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i+1,args[i]);
            }
            int i = ps.executeUpdate();
            return i;
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } finally {
        JDBCUtils.closeResource(null,ps);
        }
        return 0;
    }

    // 查询单条记录
    public <T> T getInstance (Connection conn, Class<T> clazz, String sql, Object ...args )  {
        PreparedStatement ps  = null;
        ResultSet rs  = null;
        try {
            ps = conn.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i+1, args[i]);
            }
            rs = ps.executeQuery();
            ResultSetMetaData metaData = rs.getMetaData();
            int count = metaData.getColumnCount();
            if (rs.next()){
            T t = clazz.newInstance();
            for (int i = 0; i < count; i++) {
                Object value = rs.getObject(i + 1);
                String columnLabel = metaData.getColumnLabel(i + 1);
                Field field = clazz.getDeclaredField(columnLabel);
                field.setAccessible(true);
                field.set(t,value);
            }
            return t;
            }
        }  catch (Exception e) {
            e.printStackTrace();
        } finally {
        JDBCUtils.closeResource(null,ps,rs);
        }
        return  null;
    }

    // 查询多条记录集合

    public <T> List<T> getForList(Connection conn, Class<T> clazz, String sql, Object ...args)  {
        PreparedStatement ps  = null;
        ResultSet rs  = null;
        try {
            ps = conn.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i+1, args[i]);
            }
            rs = ps.executeQuery();
            ResultSetMetaData metaData = rs.getMetaData();
            int count = metaData.getColumnCount();
            ArrayList<T> list = new ArrayList<T>();
            while (rs.next()){
                T t = clazz.newInstance();
                for (int i = 0; i < count; i++) {
                    Object value = rs.getObject(i + 1);
                    String columnLabel = metaData.getColumnLabel(i + 1);
                    Field field = clazz.getDeclaredField(columnLabel);
                    field.setAccessible(true);
                    field.set(t, value);
                }
                list.add(t);
            }
            return list;
        }  catch (Exception e) {
            e.printStackTrace();
        }
          finally {
        JDBCUtils.closeResource(null,ps,rs);
        }
        return  null;
    }

    public <E> E getValue(Connection conn, String sql, Object ...args)  {
        PreparedStatement ps  = null;
        ResultSet rs  = null;
        try {
            ps = conn.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i+1, args[i]);
            }
            rs = ps.executeQuery();
            if (rs.next()){
               return (E) rs.getObject(1);
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } finally {
        JDBCUtils.closeResource(null, ps, rs );
        }
        return null;
    }
}

2 某表接口

public interface CustomerDAO {
    // 插入数据库 insert into  xxx value (xx,xx,xx)
    void insert(Connection conn, Customer cust);

    // 删除数据
    void deleteid(Connection conn, int id);

   //更新 update zz set name =xx ...
    void update(Connection conn, Customer cust );

    // 查询返回一条，select xxx,xxx,xxx from xx where id =?
    Customer getCustomerById(Connection conn, int id);

    // 查询返回多条，select xxx,xxx,xxx from xx where id >?
    List<Customer> getCustomer(Connection conn);
    List<Customer>getCustomer2(Connection conn, int id);

    // 查询特殊值 select count(*) from xx
    Long getCount(Connection conn);

    // 查询特殊值 select max(xx) from xx
    Date getMaxDate(Connection conn);
}

3 实现

public class CustomerDAOImpl extends  BaseDAO implements  CustomerDAO{
    @Override
    public void insert(Connection conn, Customer cust) {
        String sql = "insert into customers(name,email,birth)values(?,?,?)";
        update(conn, sql, cust.getName(),cust.getEmail(),cust.getBirth());
    }

    @Override
    public void deleteid(Connection conn, int id) {
        String sql = "delete from customers where id=?";
        update(conn, sql, id);
    }

    @Override
    public void update(Connection conn, Customer cust) {
        String sql= "update customers set name=?, email=?, birth=? where id=?";
        update(conn, sql, cust.getName(), cust.getEmail(), cust.getBirth(),cust.getId());
    }

    @Override
    public Customer getCustomerById(Connection conn, int id) {
        String sql = "select id,name,email,birth from customers where id =?";
        Customer cust  = (Customer) getInstance(conn, Customer.class,sql, id);
        return cust;

    }

    @Override
    public List<Customer> getCustomer(Connection conn) {
        String sql = "select id, name, email,birth from customers";
        List<Customer> list = getForList(conn, Customer.class, sql);
        return list;
    }

    @Override
    public List<Customer> getCustomer2(Connection conn, int id ) {
        String sql = "select id, name, email,birth from customers where id > ? ";
        List<Customer> list = getForList(conn, Customer.class, sql, id);
        return  list;
    }

    @Override
    public Long getCount(Connection conn) {
        String sql = "select count(id) from customers";
        Long value = getValue(conn, sql);
        return value;
    }

    @Override
    public Date getMaxDate(Connection conn) {
        String sql = "select max(birth) from customers";
        Date value = getValue(conn, sql);
        return value;
    }
}

事物

 @Test
    public void test1() throws Exception {
        Connection connection =null;    // 确保传进来的必须是同一个连接，同时关闭自动提交
        try {
            connection = JDBCUtils.getConnection();
//            connection.setAutoCommit(false);
//            System.out.println(connection.getAutoCommit());

            connection.setAutoCommit(false);
            String sql1 = "update user_table set balance = balance - 100 where user = ?";
            update(connection,sql1,"AA");   // 确保传进来的必须是同一个连接，同时关闭自动提交

            System.out.println(10/0);
            String sql2 = "update user_table set balance = balance + 100 where user = ?";
            update(connection,sql2, "BB"); // 确保传进来的必须是同一个连接，同时关闭自动提交
            System.out.println("ok");

            connection.setAutoCommit(true);
        } catch (Exception e) {
            connection.rollback();
//            System.out.println(connection.getAutoCommit());
            e.printStackTrace();
        } finally {
            connection.setAutoCommit(true);
            JDBCUtils.closeResource(connection,null);
        }
    }

    @Test
    public void test2() throws Exception {
        Connection connection = JDBCUtils.getConnection();
        System.out.println(connection.getTransactionIsolation());

        connection.setTransactionIsolation(2);  //TRANSACTION_READ_COMMITTED 2
//        int rr  = Connection.TRANSACTION_REPEATABLE_READ;     int TRANSACTION_REPEATABLE_READ  = 4;

        System.out.println(connection.getTransactionIsolation());
        connection.close();
        Connection connection1 = JDBCUtils.getConnection();
        System.out.println(connection1.getTransactionIsolation());
    }