学步园

1、由于之前JdbcTemplate的程序需要编写一堆的RowMapper的映射文件，显得有些臃肿，最好是根据pojo类和字段的名称进行自动的对应， 所以SimpleJdbcTemplate支持使用Pojo中的属性进行自动赋值， 语法为':'开头。

public class UserDaoSpringImpl implements UserDao {
  private SimpleJdbcTemplate simpleJdbcTemplate = new SimpleJdbcTemplate(
      JdbcUtils.getDataSource());

  public void addUser(User user) {
    String sql = "insert into user (name, money, birthday) values (:name, :money, :birthday)";
    SqlParameterSource param = new BeanPropertySqlParameterSource(user);
    KeyHolder keyHolder = new GeneratedKeyHolder();
    this.simpleJdbcTemplate.getNamedParameterJdbcOperations().update(sql,
        param, keyHolder);
    user.setId(keyHolder.getKey().intValue());
  }

  public void delete(User user) {
    String sql = "delete from user where id=?";
    this.simpleJdbcTemplate.update(sql, user.getId());
  }

  public User findUser(String loginName, String password) {
    String sql = "select id, name, money, birthday    from user where name=?";
    return this.simpleJdbcTemplate.queryForObject(sql,
        ParameterizedBeanPropertyRowMapper.newInstance(User.class),
        loginName);
  }

  public User getUser(int userId) {
    String sql = "select id, name, money, birthday    from user where id=?";
    return this.simpleJdbcTemplate.queryForObject(sql,
        ParameterizedBeanPropertyRowMapper.newInstance(User.class),
        userId);
  }

  public void update(User user) {
    String sql = "update user set name=?, birthday=?, money=? where id=? ";
    this.simpleJdbcTemplate.update(sql, user.getName(), user.getBirthday(),
        user.getMoney(), user.getId());

    sql = "update user set name=:name, birthday=:birthday, money=:money where id=:id ";
    this.simpleJdbcTemplate.update(sql, new BeanPropertySqlParameterSource(
        user));
  }

}

其中使用的JdbcUtils获取数据源的代码如下：

public final class JdbcUtils {
  private static String url = "jdbc:mysql://localhost:3306/jdbc";
  private static String user = "root";
  private static String password = "";
  private static DataSource myDataSource = null;

  private JdbcUtils() {
  }

  static {
    try {
      Class.forName("com.mysql.jdbc.Driver");
      // myDataSource = new MyDataSource2();
      Properties prop = new Properties();
      // prop.setProperty("driverClassName", "com.mysql.jdbc.Driver");
      // prop.setProperty("user", "user");

      InputStream is = JdbcUtils.class.getClassLoader()
          .getResourceAsStream("dbcpconfig.properties");
      prop.load(is);
      myDataSource = BasicDataSourceFactory.createDataSource(prop);
    } catch (Exception e) {
      throw new ExceptionInInitializerError(e);
    }
  }

  public static DataSource getDataSource() {
    return myDataSource;
  }

  public static Connection getConnection() throws SQLException {
    // return DriverManager.getConnection(url, user, password);
    return myDataSource.getConnection();
  }

  public static void free(ResultSet rs, Statement st, Connection conn) {
    try {
      if (rs != null)
        rs.close();
    } catch (SQLException e) {
      e.printStackTrace();
    } finally {
      try {
        if (st != null)
          st.close();
      } catch (SQLException e) {
        e.printStackTrace();
      } finally {
        if (conn != null)
          try {
            conn.close();
            // myDataSource.free(conn);
          } catch (Exception e) {
            e.printStackTrace();
          }
      }
    }
  }
}

2、 完成相同映射的类还包括：NamedParameterJdbcTemplate， 它将之前的占位符‘？’进行了取名，方便程序的阅读。 不过这样的SQL不能再数据库中直接执行，需要有Spring进行转换。

public class NamedJdbcTemplate {
  static NamedParameterJdbcTemplate named = new NamedParameterJdbcTemplate(
      JdbcUtils.getDataSource());

  /**
    * @param args
    */
  public static void main(String[] args) {
    User user = new User();
    user.setMoney(10);
    user.setId(2);
    System.out.println(findUser1(user));
  }

  static void addUser(User user) {
    String sql = "insert into user(name,birthday, money) values (:name,:birthday,:money) ";
    SqlParameterSource ps = new BeanPropertySqlParameterSource(user);
    KeyHolder keyHolder = new GeneratedKeyHolder();
    named.update(sql, ps, keyHolder);
    int id = keyHolder.getKey().intValue();
    user.setId(id);
    
    Map map = keyHolder.getKeys();
  }

  static User findUser(User user) {
    String sql = "select id, name, money, birthday    from user "
        + "where money > :m and id < :id";
    Map params = new HashMap();
    // params.put("n", user.getName());
    params.put("m", user.getMoney());
    params.put("id", user.getId());
    Object u = named.queryForObject(sql, params, new BeanPropertyRowMapper(
        User.class));
    return (User) u;
  }

  static User findUser1(User user) {
    String sql = "select id, name, money, birthday    from user "
        + "where money > :money and id < :id";
    SqlParameterSource ps = new BeanPropertySqlParameterSource(user);
    Object u = named.queryForObject(sql, ps, new BeanPropertyRowMapper(User.class));
    return (User) u;
  }

}

【注意】

1、BeanPropertyRowMapper完成了对象到数据库字段的映射关系， 可以不再使用RowMapper来一一对应起来。如果RowMapper只使用1次，则可以直接使用内部类来完成，而不再需要专门的写一个类。

2、KeyHolder， 其中保存了数据库中操作的主键，取得操作的主键后， 方便对进行操作的记录进行其他动作。

 

总之：利用反射技术，减少的了不必要的rowmapper，提高了效率

 

转自：http://tianya23.blog.51cto.com/1081650/375823