DBUtils结果集处理器介绍

 1 import cn.itcast.jdbc.JdbcUtils;
 2 import org.apache.commons.dbutils.QueryRunner;
 3 import org.apache.commons.dbutils.handlers.*;
 4 import org.junit.Test;
 5 import java.sql.SQLException;
 6 import java.util.List;
 7 import java.util.Map;
 8 
 9 public class Demo3 {
10     @Test
11     public void fun1() throws SQLException {
12         QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
13         String sql = "INSERT INTO t_stu VALUES(?,?,?,?)";
14         Object[] params = {1002,"lisi",99,"female"};
15         qr.update(sql,params);
16     }
17     @Test
18     public void fun2() throws SQLException {
19         //创建QueryRunner，提供数据库连接池对象
20         QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
21         //给出sql模板
22         String sql = "SELECT * FROM t_stu WHERE sid=?";
23         //给出参数
24         Object[] params = {1002};
25         //执行query()方法，需要给出集处理器，即 ResultSetHandler的实现类对象
26         //我们需要给的是BeanHandler,它实现了ResultSetHandler
27         //它需要一个类型，然后它会把rs中的数据封装到指定类型的javabean对象中，然后返回javabean对象
28         Stu stu = qr.query(sql,new BeanHandler<Stu>(Stu.class),params);
29         System.out.println(stu);
30     }
31     //BeanListHandler的应用，它是多行处理器
32     //每行对象一个Stu对象
33     @Test
34     public void fun3() throws Exception{
35         QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
36         String sql = "SELECT * FROM t_stu";
37         List<Stu> stuList = qr.query(sql,new BeanListHandler<Stu>(Stu.class));
38         System.out.println(stuList);
39     }
40 
41     //MapHandler的应用，它是单行处理器，把一行转换成一个Map对象
42     @Test
43     public void fun4() throws Exception{
44         QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
45         String sql = "SELECT * FROM t_stu WHERE sid=?";
46         Object[] params = {1001};
47         Map map = qr.query(sql,new MapHandler(),params);
48         System.out.println(map);
49     }
50 
51     //MapListHandler,它是多行处理器，把每行都转换成一个Map，即List<Map>
52     @Test
53     public void fun5() throws Exception{
54         QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
55         String sql = "SELECT * FROM t_stu ";
56         List<Map<String,Object>> mapList = qr.query(sql,new MapListHandler());
57         System.out.println(mapList);
58     }@Test
59     //ScalarHandler,它是单行单列时使用，最为合适。
60     public void fun6() throws Exception{
61         QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
62         String sql = "SELECT COUNT(*) FROM t_stu ";
63         Number cnt = (Number) qr.query(sql,new ScalarHandler());
64         long c = cnt.longValue();
65         System.out.println(c);
66     }
67 }

 1 import com.mchange.v2.c3p0.ComboPooledDataSource;
 2 import java.sql.Connection;
 3 import java.sql.SQLException;
 4 
 5 public class JdbcUtils {
 6     //配置文件的默认配置，要求你必须给出从c3p0-config.xml
 7     private static ComboPooledDataSource  dataSource = new ComboPooledDataSource();
 8     //使用连接池返回一个连接对象
 9     public static Connection getConnection() throws SQLException {
10         return dataSource.getConnection();
11     }
12     //返回连接池对象
13     public static ComboPooledDataSource getDataSource() {
14         return dataSource;
15     }
16 }