Spring – RowMapper

RowMapper可以将数据中的每一行封装成用户定义的类，在数据库查询中，如果返回的类型是用户自定义的类型则需要包装，如果是Java自定义的类型，如：String则不需要，Spring最新的类SimpleJdbcTemplate使用更加简单了。
下面这个实例说明了如何使用RowMapp，从网上下载的代码，还行能说明问题。在使用过程中我们可以将内部类做成POJO的外部类，只要实现RowMapper接口即可。如果用户想让ApplicationContext进行定义还是要谨慎。毕竟实现RowMapper接口需要给一个类增加一个mapRow方法，让类承受的功能较多，不利于分析系统
实现一、在内部建立内联类实现RowMapper接口

package hysteria.contact.dao.impl;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.List;

import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;

import hysteria.contact.dao.ItemDAO;
import hysteria.contact.domain.Item;

public class ItemDAOImpl implements ItemDAO {
    private JdbcTemplate jdbcTemplate;

    public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    public Item insert(Item item) {
        String sql = "INSERT INTO items(user_id,name,phone,email) VALUES(?,?,?,?)";
        Object[] params = new Object[] { item.getUserId(), item.getName(),
                item.getPhone(), item.getEmail() };
        int[] types = new int[] { Types.INTEGER, Types.VARCHAR, Types.CHAR,
                Types.VARCHAR };
        jdbcTemplate.update(sql, params, types);
        return item;
    }

    public Item update(Item item) {
        String sql = "UPDATE items SET name = ?, phone = ?, email = ? WHERE id = ?";
        Object[] params = new Object[] { item.getName(), item.getPhone(),
                item.getEmail(), item.getId() };
        int[] types = new int[] { Types.VARCHAR, Types.CHAR, Types.VARCHAR,
                Types.VARCHAR, Types.INTEGER };
        jdbcTemplate.update(sql, params, types);

        return item;
    }

    public void delete(Item item) {
        String sql = "DELETE FROM items WHERE id = ?";
        Object[] params = new Object[] { item.getId() };
        int[] types = new int[] { Types.INTEGER };
        jdbcTemplate.update(sql, params, types);
    }

    public Item findById(int id) {
        String sql = "SELECT * FROM items WHERE id = ?";
        Object[] params = new Object[] { id };
        int[] types = new int[] { Types.INTEGER };
        List items = jdbcTemplate.query(sql, params, types, new ItemMapper());
        if (items.isEmpty()) {
            return null;
        }
        return (Item) items.get(0);
    }

    public List<Item> findAll() {
        String sql = "SELECT * FROM items";
        return jdbcTemplate.query(sql, new ItemMapper());
    }

    public List<Item> findAllByUser(int user_id) {
        String sql = "SELECT * FROM items WHERE user_id = ?";
        Object[] params = new Object[] { user_id };
        int[] types = new int[] { Types.INTEGER };
        List items = jdbcTemplate.query(sql, params, types, new ItemMapper());
        return items;
    }

    protected class ItemMapper implements RowMapper {

        public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
            Item item = new Item();
            item.setId(rs.getInt("id"));
            item.setUserId(rs.getInt("user_id"));
            item.setName(rs.getString("name"));
            item.setPhone(rs.getString("phone"));
            item.setEmail(rs.getString("email"));

            return item;
        }

    }

}