commons.dbutils1.2介绍及使用

一、结构介绍

高层结构图：

wrappers包：

handlers包（部分）:

 

二、功能介绍

commons.dbutils是一个对JDBC操作进行封装的类集，其有如下几个优点：

（1）没有可能的资源泄漏，避免了繁锁的JDBC代码

（2）代码更整洁

（3）从ResultSet自动生成JavaBeans属性

（4）无其他依赖包

 

三、基本使用

基本用到的类有：QueryRunner、ResultSetHandler及其子类等

QueryRunner -- 执行查询的类，可以执行SELECT、INSERT、UPDATE、DELETE等语句，QueryRunner用ResultSetHandler的子类来处理ResultSet并返回结果；而包提供的ResultSetHandler子类使用RowProcessor的子类来处理ResultSet中的每一行；RowProcessor的默认实现为BasicRowProcessor；BeanProcessor不是RowProcessor，可以看作一个工具类

 

ResultHandler及其子类 -- 实现了Object handle(ResultSet rs) throws SQLException方法

AbstractListHandler -- 返回多行List的抽象类

ArrayHandler --  返回一行的Object[]

ArrayListHandler -- 返回List，每行是Object[]

BeanHandler -- 返回第一个Bean对象

BeanListHandler -- 返回List，每行是Bean

ColumnListHandler -- 返回一列的List

KeyedHandler -- 返回Map，具体见代码

MapHandler -- 返回单个Map

MapListHandler -- 返回List，每行是Map

ScalarHandler -- 返回列的头一个值

代码：

//建表语句
DROP TABLE IF EXISTS `test`.`user`;
CREATE TABLE  `test`.`user` (
  `name` varchar(10) DEFAULT NULL,
  `password` varchar(10) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
表中数据
'user1', 'pwd1'
'user2', 'pwd2'
//User类
public class User {
    private String name;
    private String pwd;
    public User(){
    }
    public void setName(String val) {
        this.name = val;
    }
    public void setPassword(String val) {
        this.pwd = val;
    }
    public String getName() {
        return name;
    }
    public String getPassword() {
        return pwd;
    }
}

package dbutiltest;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;
import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.ArrayHandler;
import org.apache.commons.dbutils.handlers.ArrayListHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ColumnListHandler;
import org.apache.commons.dbutils.handlers.KeyedHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;
public class TestDbUtils {

    static {
        try {
            Class.forName("org.gjt.mm.mysql.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    public Connection getConnection() {
        Connection conn = null;
        try {
            conn = DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/test", "root", "pwd");
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }

    public static void main(String[] args) {
        TestDbUtils u = new TestDbUtils();
        u.testArrayHandler();
        u.testArrayListHandler();
        u.testBeanListHandler();
        u.testMapListHandler();
        u.testColumnListHandler();
        u.testNonQuery();
    }

    public void testArrayHandler() {
        System.out.println("----testArrayHandler----");
        String sql = "select * from user";
        ResultSetHandler handler = new ArrayHandler();
        QueryRunner query = new QueryRunner();
        Connection conn = null;
        try {
            conn = getConnection();
            Object[] arr = (Object[])query.query(conn, sql, handler);
            for (int i = 0; i < arr.length; i++) {
                System.out.println(arr[i].toString());
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                DbUtils.close(conn);
            } catch (SQLException e) {
                // ignore
            }
        }

    }

    public void testArrayListHandler() {
        System.out.println("----testArrayListHandler----");
        String sql = "select * from user";
        ResultSetHandler handler = new ArrayListHandler();
        QueryRunner query = new QueryRunner();
        Connection conn = null;
        try {
            conn = getConnection();
            List list = (List)query.query(conn, sql, handler);
            for (int i = 0; i < list.size(); i++) {
                Object[] arr = (Object[])list.get(i);
                for (int j = 0; j < arr.length; j++) {
                    System.out.print(arr[j] + "  ");
                }
                System.out.println();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                DbUtils.close(conn);
            } catch (SQLException e) {
                // ignore
            }
        }

    }

    public void testBeanListHandler() {
        System.out.println("----testBeanListHandler----");
        String sql = "select * from user where name=?";
        Object[] params = new Object[]{"user1"};
        ResultSetHandler handler = new BeanListHandler(User.class);
        QueryRunner query = new QueryRunner();
        Connection conn = null;
        try {
            conn = getConnection();
            List list = (List)query.query(conn, sql, params, handler);
            for (int i = 0; i < list.size(); i++) {
                User user = (User)list.get(i);
                System.out.println(user.getName() + "  " + user.getPassword());
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                DbUtils.close(conn);
            } catch (SQLException e) {
                // ignore
            }
        }
    }

    public void testMapListHandler() {
        System.out.println("----testMapListHandler----");
        String sql = "select * from user where name=?";
        Object[] params = new Object[]{"user1"};
        ResultSetHandler handler = new MapListHandler();
        QueryRunner query = new QueryRunner();
        Connection conn = null;
        try {
            conn = getConnection();
            List list = (List)query.query(conn, sql, params, handler);
            for (int i = 0; i < list.size(); i++) {
                Map user = (Map)list.get(i);
                System.out.println(user.get("name") + "  " + user.get("password"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                DbUtils.close(conn);
            } catch (SQLException e) {
                // ignore
            }
        }
    }

    public void testColumnListHandler() {
        System.out.println("----testColumnListHandler----");
        String sql = "select * from user";
        ResultSetHandler handler = new ColumnListHandler("name");
        QueryRunner query = new QueryRunner();
        Connection conn = null;
        try {
            conn = getConnection();
            List list = (List)query.query(conn, sql, handler);
            for (int i = 0; i < list.size(); i++) {
                System.out.println(list.get(i));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                DbUtils.close(conn);
            } catch (SQLException e) {
                // ignore
            }
        }
    }

    public void testKeyedHandler() {
        System.out.println("----testKeyedHandler----");
        String sql = "select * from user";
        ResultSetHandler handler = new KeyedHandler("name");
        QueryRunner query = new QueryRunner();
        Connection conn = null;
        try {
            conn = getConnection();
            Map map = (Map)query.query(conn, sql, handler);
            Map user = (Map)map.get("user2");
            System.out.println(user.get("password"));
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                DbUtils.close(conn);
            } catch (SQLException e) {
                // ignore
            }
        }
    }

    public void testNonQuery() {
        System.out.println("----testNonQuery----");
        String sql = "insert into `user` values('user_test','pwd_test')";
        QueryRunner query = new QueryRunner();
        Connection conn = null;
        try {
            conn = getConnection();
            query.update(conn, sql);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                DbUtils.close(conn);
            } catch (SQLException e) {
                // ignore
            }
        }
    }
}

 

 

关于wrappers包:

在新建 QueryRunner时，覆盖父类的方法wrap

QueryRunner query = new QueryRunner() {
            protected ResultSet wrap(ResultSet rs) {
                return StringTrimmedResultSet.wrap(rs);
            }
        };

 

四、扩展

1.RowProcessor接口

2.ResultSetHandler接口