Apache DBUtils使用总结

DBUtils是个小巧的JDBC轻量级封装的工具包，其最核心的特性是结果集的封装，可以直接将查询出来的结果集封装成JavaBean，这就为我们做了最枯燥乏味、最容易出错的一大部分工作。在使用DBUtils之前，应该注意一些问题：1、DBUtils是JDBC的简单封装，可以和JDBC混合使用。2、DBUtils对结果集自动封装为JavaBean是有着苛刻要求的：必须满足JavaBean的规范，其次Bean的getter与setter方法的名字与结果集的列名一一对应，而不要求JavaBean的私有成员与表结果集列名一一对应。比如：person表中有个字段叫：address，那么对应的JavaBean的Person类中必须有getAddress和setAddress两个方法，而Person类中可以将address属性命名为add，这是没问题的。3、DBUtils可以将结果集封装为各种类型，主要有：Bean/List<Bean>，Map/List<Map>/Map<Map>，数组/List<数组>，列/List<列>，这些类型。对于Map<Map>的类型使用KeyedHandler作为结果集处理器，内层的Map是“列名-值"对，外层的Map是“主键-内层Map的引用”，但此处的主键不一定就是数据库的主键，可以随意指定，比如：ResultSetHandler h = new KeyedHandler("id");Map found = (Map) queryRunner.query("select id, name, age from person", h);Map jane = (Map) found.get(new Long(1)); // jane's id is 1String janesName = (String) jane.get("name");Integer janesAge = (Integer) jane.get("age");4、DBUtils执行插入操作的时候，无法返回自增主键，这是一个很严重的问题，当然不能怪DBUtils，可以通过变通的方法来实现，比如在MySQL中，执行完了一个插入SQL后，接着执行SELECT LAST_INSERT_ID()语句，就可以获取到自增主键。5、DBUtils的性能和JDBC性能是一样，测试过程中没发现性能损失，拥有了很高性能的同时，而不失JDBC的灵活性。6、对于JavaBean的成员类型定义，有一条原则那就是：尽可能使用包装类型，而不要使用基本类型。很多人不理解为什么，包括我见到一些傻B（，我提出让改为包装类型，他还信誓旦旦的说他的代码多牛多叼），都干好多年了，这个简单的道理还不知道://错误int a1 = (Integer) null;boolean x1 = (Boolean)null;//正确Integer a2 = (Integer) null;Boolean x2 = (Boolean)null;实际上就是为了保证在查询结果为null的时候，也不会因为给基本类型赋null值而发生错误。下面给出一个简单例子，作为以后写代码时候有点参考：环境：MySQL5.4JDK1.5建表SQL：

CREATE TABLE person (id bigint(20) NOT NULL AUTO_INCREMENT,name varchar(24) DEFAULT NULL,age int(11) DEFAULT NULL,address varchar(120) DEFAULT NULL,PRIMARY KEY (id)) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=gbk

Java代码：

public class Person {private Long id;private String sdf;private String address2;private Integer age;public Person() {}public Person(String sdf) {this.sdf = sdf;}public Person(String sdf, Integer age, String address) {this.sdf = sdf;this.age = age;this.address2 = address;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getSdf() {return sdf;}public void setSdf(String sdf) {this.sdf = sdf;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public String getAddress() {return address2;}public void setAddress(String address2) {this.address2 = address2;}}

测试:

package com.lavasoft.dbstu;import com.lavasoft.common.DBToolkit;import org.apache.commons.dbutils.QueryRunner;import org.apache.commons.dbutils.handlers.BeanHandler;import org.apache.commons.dbutils.handlers.BeanListHandler;import org.apache.commons.dbutils.handlers.MapHandler;import org.apache.commons.dbutils.handlers.ScalarHandler;import java.sql.Connection;import java.sql.SQLException;import java.util.List;import java.util.Map;/*** Created by IntelliJ IDEA.** @author leizhimin 2010-1-25 21:00:29*/public class PersonDAOImpl implements PersonDAO {private static PersonDAOImpl instance = new PersonDAOImpl();public static PersonDAOImpl getInstance() {return instance;}public static void main(String[] args) {//错误int a1 = (Integer) null;boolean x1 = (Boolean) null;//正确Integer a2 = (Integer) null;Boolean x2 = (Boolean) null;getInstance().save(null);//                getInstance().save(null);//                getInstance().save(null);//                getInstance().save(null);//                getInstance().save(null);getInstance().update(null);getInstance().load(null);getInstance().load4Map(null);}@Overridepublic Long save(String sql) {Long id = null;String ins_sql = "INSERT INTO person (NAME, age, address) VALUES ('aaa', 21, 'address001')";Connection conn = DBToolkit.getConnection();QueryRunner qr = new QueryRunner();try {qr.update(conn, ins_sql);//获取新增记录的自增主键id = (Long) qr.query(conn, "SELECT LAST_INSERT_ID()", new ScalarHandler(1));} catch (SQLException e) {e.printStackTrace();} finally {DBToolkit.closeConnection(conn);}return id;}@Overridepublic int delete(Long id) {int x = 0;Connection conn = DBToolkit.getConnection();QueryRunner qr = new QueryRunner();try {x = qr.update(conn, "DELETE FROM person WHERE id = ?", id);} catch (SQLException e) {e.printStackTrace();} finally {DBToolkit.closeConnection(conn);}return x;}@Overridepublic int update(Person person) {int x = 0;Connection conn = DBToolkit.getConnection();QueryRunner qr = new QueryRunner();try {x = qr.update(conn, "UPDATE person SET NAME = ?, age = ?, address = ? WHERE id = ?", "xxx", 23, "ttt", 5);} catch (SQLException e) {e.printStackTrace();} finally {DBToolkit.closeConnection(conn);}return x;}@Overridepublic Person load(Long id) {Connection conn = DBToolkit.getConnection();QueryRunner qr = new QueryRunner();try {Person person = (Person) qr.query(conn, "SELECT * FROM person where id = ?", new BeanHandler(Person.class), 3L);System.out.println(person.getId() + "\t" + person.getSdf() + "\t" + person.getAge() + "\t" + person.getAddress());} catch (SQLException e) {e.printStackTrace();}return null;}@Overridepublic List<Person> findPerson(String sql) {Connection conn = DBToolkit.getConnection();QueryRunner qr = new QueryRunner();try {List<Person> pset = (List) qr.query(conn, "SELECT * FROM person", new BeanListHandler(Person.class));for (Person person : pset) {System.out.println(person.getId() + "\t" + person.getSdf() + "\t" + person.getAge() + "\t" + person.getAddress());}} catch (SQLException e) {e.printStackTrace();}return null;}public Person load4Map(Long id) {Connection conn = DBToolkit.getConnection();QueryRunner qr = new QueryRunner();try {//先将两个字段置为nullqr.update(conn, "update person set age = null,address =null where id =1");Map<String, Object> map = qr.query(conn, "SELECT * FROM person where id = ?", new MapHandler(), 1L);Person person = new Person();person.setId((Long) map.get("id"));person.setSdf((String) map.get("name"));person.setAge((Integer) map.get("age"));person.setAddress((String) map.get("address"));System.out.println(person.getId() + "\t" + person.getSdf() + "\t" + person.getAge() + "\t" + person.getAddress());} catch (SQLException e) {e.printStackTrace();}return null;}}

注意：从上面的过程看，每个SQL的执行都需要用到QueryRunner，这其实是一个普通的类，非线程安全。在创建这个QueryRunner对象的时候，每次都要new。QueryRunner对象的创建方式很多，可以通过DateSource，也可以通过Connection来创建。从QueryRunner对象上，可以直接获取到DataSource或者Connection对象。Dbutil 的使用示例

代码package cn.lining.test;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.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.MapHandler;import org.apache.commons.dbutils.handlers.MapListHandler;import org.apache.commons.dbutils.handlers.ScalarHandler;publicclass test {@SuppressWarnings("unchecked")publicstaticvoid main(String[] args) throws ClassNotFoundException {UserField userField =new UserField();Connection conn =null;String jdbcURL ="jdbc:mysql://localhost:3306/macaw4";String jdbcDriver ="com.mysql.jdbc.Driver";try {DbUtils.loadDriver(jdbcDriver);conn = DriverManager.getConnection(jdbcURL, "root", "root");conn.setAutoCommit(false);//关闭自动提交QueryRunner qRunner =new QueryRunner();// 以下部分代码采用MapHandler存储方式查询System.out.println("***Using MapHandler***");Map map = (Map) qRunner.query(conn,"select * from mc_user_field where id = ?",new MapHandler(), new Object[] { "5" });System.out.println("id ------------- name ");System.out.println(map.get("id") +"  ------------- "+ map.get("name"));// 以下部分代码采用MapListHandler存储方式查询System.out.println("***Using MapListHandler***");List lMap = (List) qRunner.query(conn,"select * from mc_user_field", new MapListHandler());System.out.println("id ------------- name ");for (int i =0; i < lMap.size(); i++) {Map vals = (Map) lMap.get(i);System.out.println(vals.get("id") +"  ------------- "+ vals.get("name"));}// 以下部分代码采用BeanHandler存储方式查询System.out.println("***Using BeanHandler***");userField = (UserField) qRunner.query(conn,"select * from mc_user_field where id = ?",new BeanHandler(Class.forName("cn.lining.test.UserField")),new Object[] { "5" });System.out.println("id ------------- name ");System.out.println(userField.getId() +"  ------------- "+ userField.getName());// 以下部分代码采用BeanListHandler存储方式查询System.out.println("***Using BeanListHandler***");List lBean = (List) qRunner.query(conn,"select * from mc_user_field", new BeanListHandler(Class.forName("cn.lining.test.UserField")));System.out.println("id ------------- name ");for (int i =0; i < lBean.size(); i++) {userField = (UserField) lBean.get(i);System.out.println(userField.getId() +"  ------------- "+ userField.getName());}// 以下部分代码采用ArrayHandler存储方式查询System.out.println("***Using ArrayHandler***");Object[] array = (Object[]) qRunner.query(conn,"select * from mc_user_field where id = ?",new ArrayHandler(), new Object[] { "5" });System.out.println("id ------------- name ");System.out.println(array[0].toString() +"  ------------- "+ array[1].toString());// 以下部分代码采用ArrayListHandler存储方式查询System.out.println("***Using ArrayListHandler***");List lArray = (List) qRunner.query(conn,"select * from mc_user_field", new ArrayListHandler());System.out.println("id ------------- name ");for (int i =0; i < lArray.size(); i++) {Object[] var = (Object[]) lArray.get(i);System.out.println(var[0].toString() +"  ------------- "+ var[1].toString());}// 以下部分代码采用ColumnListHandler存储方式查询指定列System.out.println("***Using ColumnListHandler***");List lName = (List) qRunner.query(conn,"select * from mc_user_field where id = ?",new ColumnListHandler("name"), new Object[] { "5" });System.out.println("name ");for (int i =0; i < lName.size(); i++) {String name = (String) lName.get(i);System.out.println(name);}// 以下部分代码采用ScalarHandler存储方式查询System.out.println("***Using ScalarHandler***");String name = (String) qRunner.query(conn,"select * from mc_user_field where id = ?",new ScalarHandler("name"), new Object[] { "5" });System.out.println("name ");System.out.println(name);// 以下部分代码采用KeyedHandler存储方式查询System.out.println("***Using KeyedHandler***");Map<String, Map> map2 = (Map<String, Map>) qRunner.query(conn,"select * from mc_user_field", new KeyedHandler("name"));System.out.println("name: field_name2");Map vals = (Map) map2.get("field_name2");System.out.println(vals.get("id") +""+ vals.get("name") +""+ vals.get("type"));// 以下部分代码插入一条数据System.out.println("***Insert begin***");userField =new UserField();qRunner.update(conn, "insert into mc_user_field ("+"id,name,type,sort_order,required,visible)"+"values (?,?,?,?,?,?)", new Object[] { userField.getId(),userField.getName(), userField.getType(),userField.getSort_order(), userField.getRequired(),userField.getVisible() });System.out.println("***update end***");// 以下部分代码更新一条数据System.out.println("***update begin***");userField =new UserField();qRunner.update(conn, "update mc_user_field set "+"name = ?,type = ?,sort_order = ?,"+"required = ?,visible = ?"+"where id = ?",new Object[] { userField.getName(), userField.getType(),userField.getSort_order(), userField.getRequired(),userField.getVisible(), userField.getId() });System.out.println("***update end***");// 以下部分代码删除一条数据System.out.println("***delete begin***");userField =new UserField();qRunner.update(conn, "delete from mc_user_field where id2 = ?",new Object[] { userField.getId() });System.out.println("***delete end***");} catch (SQLException ex) {ex.printStackTrace();try {System.out.println("***rollback begin***");DbUtils.rollback(conn);System.out.println("***rollback end***");} catch (SQLException e) {e.printStackTrace();}} finally {DbUtils.closeQuietly(conn);}}}

ArrayHandler：把结果集中的第一行数据转成对象数组。ArrayListHandler：把结果集中的每一行数据都转成一个对象数组，再存放到List中。BeanHandler：将结果集中的第一行数据封装到一个对应的JavaBean实例中。BeanListHandler：将结果集中的每一行数据都封装到一个对应的JavaBean实例中，存放到List里。ColumnListHandler：将结果集中某一列的数据存放到List中。KeyedHandler：将结果集中的每一行数据都封装到一个Map里，然后再根据指定的key把每个Map再存放到一个Map里。MapHandler：将结果集中的第一行数据封装到一个Map里，key是列名，value就是对应的值。MapListHandler：将结果集中的每一行数据都封装到一个Map里，然后再存放到List。ScalarHandler：将结果集中某一条记录的其中某一列的数据存成Object。