Apache DBUtils使用总结 【转】
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?
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; }}?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); } @Override public 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; } @Override public 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; } @Override public 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; } @Override public 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; } @Override public 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null qr.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 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;public class test { @SuppressWarnings("unchecked") public static void 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); } }}??ScalarHandler：将结果集中某一条记录的其中某一列的数据存成Object。