JdbcTemplate总结

1.您可以使用JdbcTemplate的execute()方法執行SQL DDL语句，例如：

jdbcTemplate.execute("CREATE TABLE USER (user_id integer, name varchar(100))");

使用JdbcTemplate进行查询时，可以使用queryForXXX()等方法，例如使用queryForInt()方法传回user表格中的数据数目： jdbcTemplate.quertForInt("select count(*) from user"); 也可以使用queryForObject()传回一个查询后的对象，例如传回一个String对象：

String name=(String)jdbcTemplate.queryForObject(
　　　　         "selcet name from user where id=?",
                         new Object[]{id},
                         java.lang.String.class);
)



单独查询某个数据并赋值给特定对象时：


    public BaseObj getBaseObj(final int ID) {

        String sql = "select * from " + DB_TABLE_NAME + " where NewsId=" + ID;
        BaseObj obj =(BaseObj) getJdbcTemplate().query(sql,new ResultSetExtractor(){
            public Object extractData(ResultSet rs) throws SQLException,DataAccessException {
                if (rs.next()) {
                    NewsObj news = new NewsObj();
                    news.setID(rs.getInt("NewsID"));
                    news.setTitle(rs.getString("NewsTitle"));
                    news.setBigClass(rs.getInt("BigClassId"));
                    news.setNewsContent(rs.getString("NewsContent"));
                    news.setNewsKey(rs.getString("NewsKey"));
                    news.setNewsAuthor(rs.getString("NewsAuthor"));
                    news.setImg(rs.getBoolean("isImg"));
                    news.setNewsFrom(rs.getString("NewsFrom"));
                    return news;
                }
                return null;
            }
        });
       return obj;

    }


上面两个例子都是传回单独一笔数据，如果要传回多笔数据，则可以使用queryForList()方法，例如：
List rows=jdbcTemplate().queryForList("select * from user where id="+id.intValue()); 传回的list中包括的是map对象，每个map对象代表查询结果中的一笔数据，每笔数据包括多个字段，要取得字段中的值，就要使用字段名作为key,例如：

   Iterator it=rows.iterator();
   while(it.hasNext()){
       Map result=(Map)it.next();
       System.out.println(userMap.get("id"));
       System.out.println(userMap.get("name"));
       System.out.println(userMap.get("age"));
    }



在查询的同时，你可以在返回结果之前先进行一些处理，这就要实现RowCallbackHandler接口

public User find(Integer id){
   final User user=new User();
   jdbcTemplate.query("select * from user where id=?",new Object[]{id},
                                         new RowCallBackHandler(){
                                                public void proccessRow(ResultSet rs){
                                                        user.setId(new Integer(rs.getInt("id")));
                                                        uset.setName(rs.getString("name"));   
                                                 }
                                            });
   return user;
}

如果一次要返回多个查询结果对象，则可以实现RowMapper接口

public class UserRowMapper implements RowMapper{
       public Object MapRow(ResultSet rsmint rowNum) throws SQLException{
               User user=new User();
               user.setId(new Integer(rs.getInt("id")));
               user.setName(rs.getString("name"));
               return user;
      }
}

使用RowMapper查询单笔数据

public User find(Integer id){
        User user=(User)jdbcTemplate.queryForObject("select * from user where id=?",new Object[]{id},
                                                                                    new UserRowMapper());
         return user;

}

使用RowMapper查询多笔数据



class UserRowMapper implements RowMapper {

        public Object mapRow(ResultSet rs,int index) throws SQLException

        {
            User u = new User();
            u.setId(rs.getString(”ID”));
            u.setName(rs.getString(”Name”));
            u.setPassword(rs.getString(”Password”));
            return u;

        }

    }

public List select(String where)

    {

        List list;       
        String sql = “select * from admin “+where;       
        list = jdbcTemplate.query(sql,new RowMapperResultReader(new UserRowMapper()));
        return list;

    }




传回的users对象中，包括了从数据库查询出来的结果，并已经封装成uer对象