上一篇文章是我们自己模拟的DBUtils工具类，其实有开发好的工具类
这里使用commons-dbutils-1.6.jar
事务的简单介绍：
在数据库中应用事务处理案例：转账案例
张三和李四都有有自己的存款
主键 帐户名 余额
1 张三 1000
2 李四 10
要从张三的账户余额中转账800到李四账户
SQL语句实现：
update xx set 余额 = 余额-800 where 主键=1
update xx set 余额 = 余额+800 where 主键=2
虽然操作成功，但是会出现问题，如果张三余额不足800，那么转账结束后余额是负数，显然有问题
而数据库本身不会判断是否为负数
所以数据库就将这两个操作包装成一个事务，执行结果有两种，成功或者失败，不可以分开执行
执行成功称：提交事务，执行失败称：回滚事务
对数据表的操作：
表的创建：
CREATE TABLE sort( sid INT PRIMARY KEY AUTO_INCREMENT, sname VARCHAR(100), sprice DOUBLE, sdesc VARCHAR(5000));
QueryRunner类的方法实现表的增删改：
package demo;import java.sql.Connection;import java.sql.SQLException;import org.apache.commons.dbutils.DbUtils;import org.apache.commons.dbutils.QueryRunner;public class QueryRunnerDemo { private static Connection con = JDBCUtils.getConnection(); public static void main(String[] args) throws SQLException { // 这三个方法不能同时执行，测试时候应该注释掉不使用的 // 因为每一个方法最后都关闭了数据库连接 // insert(); // update(); delete(); } public static void insert() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "INSERT INTO sort (sname,sprice,sdesc)VALUES(?,?,?)"; Object[] params = { "篮球", 266, "体育用品" }; int row = qr.update(JDBCUtils.getConnection(), sql, params); System.out.println(row); DbUtils.closeQuietly(con); } public static void update() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "UPDATE sort SET sname=?,sprice=?,sdesc=? WHERE sid=?"; Object[] params = { "足球", 255, "出售足球", 8 }; int row = qr.update(con, sql, params); System.out.println(row); DbUtils.closeQuietly(con); } public static void delete() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "DELETE FROM sort WHERE sid=?"; int row = qr.update(con, sql, 8); System.out.println(row); DbUtils.closeQuietly(con); }}// 三种方法如果输出1表示执行成功，输出0表示执行失败
自定义的工具：
package demo;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.util.Properties;public class JDBCUtils { private static Connection con; private static String driverClass; private static String url; private static String username; private static String password; static { try { readConfig(); Class.forName(driverClass); con = DriverManager.getConnection(url, username, password); } catch (Exception ex) { throw new RuntimeException("数据库连接失败"); } } private static void readConfig() throws Exception { InputStream in = JDBCUtils.class.getClassLoader().getResourceAsStream("database.properties"); Properties pro = new Properties(); pro.load(in); driverClass = pro.getProperty("driverClass"); url = pro.getProperty("url"); username = pro.getProperty("username"); password = pro.getProperty("password"); } public static Connection getConnection() { return con; }}
配置文件：database.properties
driverClass=com.mysql.jdbc.Driverurl=jdbc:mysql://localhost:3306/mybaseusername=rootpassword=xuyiqing
QueryRunner类查询：
这里有多种结果集的处理方式：
package demo;import java.sql.Connection;import java.sql.SQLException;import java.util.List;import java.util.Map;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.MapHandler;import org.apache.commons.dbutils.handlers.MapListHandler;import org.apache.commons.dbutils.handlers.ScalarHandler;public class QueryRunnerDemo { private static Connection con = JDBCUtils.getConnection(); public static void main(String[] args) throws SQLException { arrayHandler(); arrayListHandler(); beanHandler(); beanListHandler(); scalarHandler(); mapHandler(); mapListHandler(); } public static void arrayHandler() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "SELECT * FROM sort"; Object[] result = qr.query(con, sql, new ArrayHandler()); for (Object obj : result) { System.out.print(obj + "\t"); } // 打印第一行的数据 } public static void arrayListHandler() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "SELECT * FROM sort"; List<Object[]> result = qr.query(con, sql, new ArrayListHandler()); for (Object[] objs : result) { for (Object obj : objs) { System.out.print(obj + "\t"); } System.out.println(); } // 打印了全部的数据 } public static void beanHandler() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "SELECT * FROM sort"; Sort sort = qr.query(con, sql, new BeanHandler<Sort>(Sort.class)); System.out.println(sort); // 第一行的数据变成sort对象，打印对象的toString方法 // 这种方法需要特别注意：sort类中必须有空参构造器 } public static void beanListHandler() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "SELECT * FROM sort"; List<Sort> list = qr.query(con, sql, new BeanListHandler<Sort>(Sort.class)); for (Sort s : list) { System.out.println(s); } // 所有数据变成sort对象，装入list集合，打印出多个对象 } public static void scalarHandler() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "SELECT COUNT(*) FROM sort"; long count = qr.query(con, sql, new ScalarHandler<Long>()); System.out.println(count); // 适合于处理单结果集 } public static void mapHandler() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "SELECT * FROM sort"; Map<String, Object> map = qr.query(con, sql, new MapHandler()); for (String key : map.keySet()) { System.out.println(key + "\t" + map.get(key)); } // 打印第一行数据，键值对 } public static void mapListHandler() throws SQLException { QueryRunner qr = new QueryRunner(); String sql = "SELECT * FROM sort"; List<Map<String, Object>> list = qr.query(con, sql, new MapListHandler()); for (Map<String, Object> map : list) { for (String key : map.keySet()) { System.out.println(key + "\t" + map.get(key)); } } // 所有数据转成map集合，再存入List集合 }}
附加：
这里用到了和表名一致的一个自定义类，sort类：
package demo;public class Sort { private int sid; private String sname; private double sprice; private String sdesc; public Sort(int sid, String sname, double sprice, String sdesc) { this.sid = sid; this.sname = sname; this.sprice = sprice; this.sdesc = sdesc; } public Sort() { } public int getSid() { return sid; } public void setSid(int sid) { this.sid = sid; } public String getSname() { return sname; } public void setSname(String sname) { this.sname = sname; } public double getSprice() { return sprice; } public void setSprice(double sprice) { this.sprice = sprice; } public String getSdesc() { return sdesc; } public void setSdesc(String sdesc) { this.sdesc = sdesc; } @Override public String toString() { return "Sort [sid=" + sid + ", sname=" + sname + ", sprice=" + sprice + ", sdesc=" + sdesc + "]"; }}
旅行要学会随遇而安，淡然一点，
