dbutils开源项目用法

Common Dbutils是操作数据库的组件，对传统操作数据库的类进行二次封装，可以把结果集转化成List。


DBUtils包括3个包：
org.apache.commons.dbutils
org.apache.commons.dbutils.handlers
org.apache.commons.dbutils.wrappers
DBUtils封装了对JDBC的操作，简化了JDBC操作，可以少写代码。

org.apache.commons.dbutils
DbUtils 关闭链接等操作
QueryRunner 进行查询的操作

org.apache.commons.dbutils.handlers
ArrayHandler ：将ResultSet中第一行的数据转化成对象数组
ArrayListHandler将ResultSet中所有的数据转化成List，List中存放的是Object[]
BeanHandler ：将ResultSet中第一行的数据转化成类对象
BeanListHandler ：将ResultSet中所有的数据转化成List，List中存放的是类对象
ColumnListHandler ：将ResultSet中某一列的数据存成List，List中存放的是Object对象
KeyedHandler ：将ResultSet中存成映射，key为某一列对应为Map。Map中存放的是数据
MapHandler ：将ResultSet中第一行的数据存成Map映射
MapListHandler ：将ResultSet中所有的数据存成List。List中存放的是Map
ScalarHandler ：将ResultSet中一条记录的其中某一列的数据存成Object

org.apache.commons.dbutils.wrappers
SqlNullCheckedResultSet ：对ResultSet进行操作，改版里面的值
StringTrimmedResultSet ：去除ResultSet中中字段的左右空格。

QueryRunner

构造 QueryRunner ： 有两种方法来构造QueryRunner 一种是无参数的 一种是有DataSource类型参数的构造方法

1:QueryRunner()    2:QueryRunner(javax.sql.DataSource ds)

这里使用DataSource 来构造它 使用连接池来构造它的好处就是 我们无需管Connection 对象的创建与关闭了,后面调用QueryRunner对象的方法也无需传入Connection对象了

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/** 
* dbcp连接池的用法 
*/  
public class DBUtils {  
private static Properties properties;  
private static DataSource dataSource;  
private static Connection conn;  
static {  
try {  
properties = new Properties();  
//载入dbcp的配置文件  
properties.load(DBUtils.class.  
.getResourceAsStream("/dbcpconfig.properties"));  
//创建个BasicDataSourceFactory对象用于创建连接池对象  
BasicDataSourceFactory b = new BasicDataSourceFactory();  
//把properties对象设置给BasicDataSourceFactory  
dataSource = b.createDataSource(properties);  
} catch (Exception e) {  
e.printStackTrace();  
}  
}  
public static DataSource getdataSource() {  
return dataSource;  
}  
}  


注意：需要导入dbcp连接池的jar commons-dbcp-1.2.1.jar 和所依赖的 commons-pool-1.2.jar 和commons-collections-3.1.jar

这样我们就可以构造个queryRunner对象了

QueryRunner queryRunner = new QueryRunner(DBUtils.getdataSource());

QueryRunner 主要方法 ：

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//更新一列  
queryRunner.update("update Users set username=?,password=? where id = ?", new String[]{"11","22","1"});  
//删除一列  
queryRunner.update("delete from Users where id =?", 1);  



如果要 使用 QueryRunner的查询方法 也就是query()方法的话 那么就需要有对象来接收查询出来的ResultSet

用什么来接收呢？ 要用到 实现ResultSetHandler 接口的类

1. BeanHandler 返回个entitybean 对象

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//指定返回哪个 entitybean  
ResultSetHandler rsh = new BeanHandler(Users.class);  
QueryRunner queryRunner = new QueryRunner(DBUtils.getdataSource());  
Users users = (Users) queryRunner.query("select * from Users where id=?",2, rsh);  
System.out.println(users.getUsername());  


2. BeanListHandler 返回个List List里装的是entitybean 对象

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QueryRunner queryRunner = new QueryRunner(DBUtils.getdataSource());  
ResultSetHandler rsh = new BeanListHandler(Users.class);  
List<Users> list = (List) queryRunner.query(  
"select * from Users ", rsh);  
for(Users user:list){  
System.out.println(user.getUsername());  
}  


3. ArrayListHandler 返回List 对象 list里装的为Object数组

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QueryRunner queryRunner = new QueryRunner(DBUtils.getdataSource());  
// 使用ArrayListHandler 实现类来存放结果会返回ArrayList对象  
ResultSetHandler rsh = new ArrayListHandler();  
//list里装的是对象数组  
List<Object[]> list = (List) queryRunner.query(  
"select * from Users ", rsh);  
for(Object[] user:list) {  
for(Object obj:user)  
{  
System.out.println(obj);  
}  
}  


4. ColumnListHandler 返回List 对象
注意: 构造 ColumnListHandler() 对象时候如果 是无参数的话 像这样 ResultSetHandler rsh = new ColumnListHandler(); 查询出来的List 里放的类型为主键的类型 值为主键的值;

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ResultSetHandler rsh = new ColumnListHandler();  
List<Integer> list = (List) queryRunner.query(  
"select * from Users ", rsh);  
//System.out.println(list.get(0).getClass().getSimpleName());  
for(Integer in:list){  
System.out.println(in);  
}  


构造 ColumnListHandler() 对象时候如果 是有参数的话 ，像这样 ResultSetHandler rsh = new ColumnListHandler(主键值); 那么查询出来的List 里放的是就是这个主键对应的一行的记录;

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ResultSetHandler rsh = new ColumnListHandler(2);  
List<String> list = (List) queryRunner.query(  
"select * from Users ", rsh);  
for(String in:list){  
System.out.println(in);  
}  


5. KeyedHandler 根据键返回Map

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ResultSetHandler rsh = new KeyedHandler();  
//map里装的key为主键的值 value 为主键对应的那行记录名称和记录  
Map map = (Map) queryRunner.query(  
"select id,username,password from Users ", rsh);  
//根据主键值出去那一列  
// Map t = (Map) map.get(2);  
System.out.println(map.get(2));  



6. MapHandler 根据键返回Map

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QueryRunner queryRunner = new QueryRunner(DBUtils.getdataSource());  
ResultSetHandler rsh = new MapHandler();  
Map map = (Map) queryRunner.query(  
"select * from Users ", rsh);  
System.out.println(map);  


下面给出一个完整的例子，建立三个Java文件

BeanListExample.java

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package com.sy; 
import org.apache.commons.dbutils.DbUtils; 
import org.apache.commons.dbutils.QueryRunner; 
import org.apache.commons.dbutils.handlers.BeanListHandler; 
import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.SQLException; 
import java.util.List; 
public class BeanListExample { 
    public static void main(String[] args) { 
        Connection conn = null; 
        String url = "jdbc:mysql://localhost:3306/people"; 
        String jdbcDriver = "com.mysql.jdbc.Driver"; 
        String user = "root"; 
        String password = "hicc"; 
        DbUtils.loadDriver(jdbcDriver); 
        try { 
            conn = DriverManager.getConnection(url, user, password); 
            QueryRunner qr = new QueryRunner(); 
            List results = (List) qr.query(conn, "select id,name from guestbook", new BeanListHandler(Guestbook.class)); 
            for (int i = 0; i < results.size(); i++) { 
                Guestbook gb = (Guestbook) results.get(i); 
                System.out.println("id:" + gb.getId() + ",name:" + gb.getName()); 
            } 
        } catch (SQLException e) { 
            e.printStackTrace(); 
        } finally { 
            DbUtils.closeQuietly(conn); 
        } 
    } 
} 


Guestbook.java

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package com.sy; 
public class Guestbook { 
    private Integer id; 
    private String name; 
    public Integer getId() { 
        return id; 
    } 
    public void setId(Integer id) { 
        this.id = id; 
    } 
    public String getName() { 
        return name; 
    } 
    public void setName(String name) { 
        this.name = name; 
    } 
} 


MapListExample.java

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package com.sy; 
import org.apache.commons.dbutils.DbUtils; 
import org.apache.commons.dbutils.QueryRunner; 
import org.apache.commons.dbutils.handlers.MapListHandler; 
import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.SQLException; 
import java.util.List; 
import java.util.Map; 
public class MapListExample { 
    public static void main(String[] args) { 
        Connection conn = null; 
        String url = "jdbc:mysql://localhost:3306/people"; 
        String jdbcDriver = "com.mysql.jdbc.Driver"; 
        String user = "root"; 
        String password = "hicc"; 
        DbUtils.loadDriver(jdbcDriver); 
        try { 
            conn = DriverManager.getConnection(url, user, password); 
            QueryRunner qr = new QueryRunner(); 
            List results = (List) qr.query(conn, "select id,name from guestmessage", new MapListHandler()); 
            for (int i = 0; i < results.size(); i++) { 
                Map map = (Map) results.get(i); 
                System.out.println("id:" + map.get("id") + ",name:" + map.get("name")); 
            } 
        } catch (SQLException e) { 
            e.printStackTrace(); 
        } finally { 
            DbUtils.closeQuietly(conn); 
        } 
    } 
}