Spring JdbcTemplate 查询方法中的RowMapper实现汇总

sping中的RowMapper可以将数据中的每一行数据封装成用户定义的类.

我们在数据库查询中，如果返回的类型是用户自定义的类型(其实我们在数据库查询中大部分返回的都是自定义的类)则需要包装，如果是Java自定义的类型，如：String则不需要.

如果sping与hibernate 相结合了,基本上是用不到,大多数都是在spring单独使用时用到.

可以通过建立内部类实现RowMapper接口,RowMapper中有一个mapRow方法,所以实现RowMapper接口一定要实现mapRow方法,而对自定义类的包装就在mapRow方法中实现.

这里只是一个简单的例子:

public class TestDao {
private JdbcTemplate jt;
public void setJt(JdbcTemplate jt) {
this.jt = jt;
}
public List<TNpc> getAll(){
String sql = "select * from t_npc";
//使用
List list = jt.query(sql, new NpcRowMapper());
return list;
}
/**
* 定义内部类实现RowMapper接口
*/
public class NpcRowMapper implements RowMapper{
//实现mapRow方法
public Object mapRow(ResultSet rs, int num) throws SQLException {
//对类进行封装
TNpc npc = new TNpc();
npc.setId(rs.getLong("id"));
npc.setName(rs.getString("name"));
return npc;
}
}
}

Java代码


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;

}

}

}