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