dbutils开源项目用法

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。Trim[size=large]

dbutils 开源项目用法：

项目地址：http://commons.apache.org/dbutils/
最新版本为 1.1

英文文档中这样写到：

DbUtils is a very small library of classes so it won't take long to go throughthe javadocs for each class.

The core classes/interfaces in DbUtils are QueryRunner and ResultSetHandler.

You don't need to know about any other DbUtils classes to benefit from usingthe library.

大概意思是： DbUtils 是一个非常小的类库因此你不需要花费太长的时间去研究javadocs

    它的核心接口是 QueryRunner 和ResultSetHandler

    你不需要关心其他DbUtils的类如何使用

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QueryRunner
构造 QueryRunner ：
QueryRunner()
QueryRunner(javax.sql.DataSource ds)

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对象了那我们就要用到另外一个开源数据库连接池组件dbcp以下为dbcp的用法：

Java代码

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;

}

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jarcommons-dbcp-1.2.1.jar 和所依赖的commons-pool-1.2.jar

commons-collections-3.1.jar

Java代码

//这样我们就可以构造个queryRunner对象了

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

//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：

Java代码

//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);

//更新一列

queryRunner.update("update Users setusername=?,password=? where id = ?", newString[]{"11","22","1"});

//删除一列

　　　 queryRunner.update("delete from Users where id =?", 1);

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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

Java代码

//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());

//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 Userswhere id=?",2, rsh);

System.out.println(users.getUsername());

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

Java代码

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());

}

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());

}

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

Java代码

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);

}

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;

Java代码

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);

}

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 = newColumnListHandler(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; Java代码

ResultSetHandler rsh = new ColumnListHandler(2);

List<String> list = (List) queryRunner.query(

"select * from Users ", rsh);

for(String in:list){

System.out.println(in);

}

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

Java代码

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));

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));

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6. MapHandler 根据键返回Map

Java代码

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

ResultSetHandler rsh = new MapHandler();

Map map = (Map) queryRunner.query("select * from Users ", rsh); System.out.println(map);

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

ResultSetHandler rsh = new MapHandler();

Map map = (Map) queryRunner.query(

"select * from Users ", rsh);

System.out.println(map);

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7. ScalarHandler 根据键返回第一行记录

Java代码

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

// 这样就会返回第一行记录名字为username的值

ResultSetHandler rsh = new ScalarHandler("username");

//这的类型根据表里数据的类型而定如果上面

ResultSetHandler rsh = new ScalarHandler("username");

//取出来的类型为int的话那么这里也必须由int 来接收

String result = (String) queryRunner.query("select * from Users where id=99 ", rsh);

System.out.println(result);

廖世勇