使用DBUtils连接数据库

前言：使用C3P0连接池连接MySql

1.导入相应的JARs

MySQL驱动jar包：mysql-connector-Java-5.1.28-bin.jar

C3P0需要的jar包：c3p0-0.9.2-pre1.jar和mchange-commons-0.2.jar

2.在src下添加C3P0配置文件：c3p0-config.xml

 xml version="1.0" encoding="UTF-8"?>
 <c3p0-config>
     <default-config>
         <property name="jdbcUrl">jdbc:mysql://localhost:3306/grainproperty>
         <property name="driverClass">com.mysql.jdbc.Driverproperty>
         <property name="user">rootproperty>
         <property name="password">123property>

         <property name="acquireIncrement">3property>
         <property name="initialPoolSize">10property>
         <property name="minPoolSize">2property>
         <property name="maxPoolSize">10property>
     default-config>
 c3p0-config>

3.封装为JdbcUtils，用来获取Connection对象，以及开启和关闭事务。有以下接口：

• Connection getConnection()：从c3p0连接池获取Connection对象，所以需要提供c3p0-config.xml配置文件；

• beginTransaction()：为当前线程开启事务；

• commitTransaction()：提交当前线程的事务；

• rollbackTransaction()：回滚当前线程的事务；

• releaseConnection(Connection)：如果参数连接对象不是当前事务的连接对象，那么关闭它，否则什么都不做；

4.测试JdbcUtils

 @Test
     public void testJdbcUtils() throws SQLException {
         Connection con = JdbcUtils.getConnection();
         System.out.println(con);
         JdbcUtils.releaseConnection(con);
         System.out.println(con.isClosed());
     }

5.封装TxQueryRunner，使用JdbcUtils连接数据库，使用QueryRunner简化数据库操作

引入jar包：commons-dbutils-1.4.jar，有以下接口：

• int[] batch(String sql, Object[][] params)：执行批处理，参数sql是SQL语句模板，params为参数；

• T query(String sql, ResultSetHandler rh)：执行查询，执行查询，参数sql为要执行的查询语句模板，rh是结果集处理，用来把结果集映射成你想要的结果；

• T query(String sql, ResultSetHandler rh, Object… params)：执行查询，参数sql为要执行的查询语句模板，rh是结果集处理，用来把结果集映射成你想要的结果，params是sql语句的参数；

• int update(String sql)：执行增、删、改语句，参数sql是要执行的SQL语句；

• int update(Stringsql, Object param)：执行增、删、改语句，参数sql是要执行的SQL语句，参数param是参数（一个参数）；

• int update(String sql, Object… params)：执行增、删、改语句，参数sql是要执行的SQL语句，参数params是参数（多个参数）；

6.测试TxQueryRunner

 @Test
     public void testUpdate() throws SQLException {
         String sql = "insert into user_info(uid,uname,phonenumber,region,address,postcode) values(?,?,?,?,?,?)";
         Object[] params = {"0001","xiaoming","12345678912","China","Beijing","123456"};
         QueryRunner q = new TxQueryRunner();
         q.update(sql,params);
     }
     @Test
     public void testUpdate2() throws SQLException {
         try{
             JdbcUtils.beginTransaction();
             String sql = "insert into user_info(uid,uname,phonenumber,region,address,postcode) values(?,?,?,?,?,?)";
             Object[] params1 = {"0002","xiaoming","12345678912","China","Beijing","123456"};
             Object[] params2 = {"0003","xiaoming","12345678912","China","Beijing","123456"};
             QueryRunner q = new TxQueryRunner();
             q.update(sql,params1);
             q.update(sql,params2);
             JdbcUtils.commitTransaction();
         }catch(Exception e){
             try{
                 JdbcUtils.rollbackTransaction();
             }catch(SQLException ee){
             }
         }
     }
     //单行结果集，BeanHandler
     @Test
     public void testQuery() throws SQLException{
         String sql = "select * from user_info where uid = ?";
         QueryRunner q = new TxQueryRunner();
         User u = q.query(sql, new BeanHandler(User.class),"0001");
         System.out.println(u);
     }
     //多行结果集，BeanListHandler
     @Test
     public void testQuery2() throws SQLException{
         String sql = "select * from user_info";
         QueryRunner q = new TxQueryRunner();
         List list_u = q.query(sql, new BeanListHandler(User.class));
         System.out.println(list_u);
     }
     //单行结果集，map
     @Test
     public void testQuery3() throws SQLException{
         String sql = "select * from user_info where uid = ?";
         QueryRunner q = new TxQueryRunner();
         Map map_u = q.query(sql, new MapHandler(),"0001");
         System.out.println(map_u);
     }
     //多行结果集，List
     @Test
     public void testQuery4() throws SQLException{
         String sql = "select * from user_info";
         QueryRunner q = new TxQueryRunner();
         List> list_map_u = q.query(sql, new MapListHandler());
         System.out.println(list_map_u);
     }
     //单行单列，ScalarHandler
     @Test
     public void testQuery5() throws SQLException{
         String sql = "select count(*) from user_info";
         QueryRunner q = new TxQueryRunner();
         Object obj = q.query(sql, new ScalarHandler());
         //select count(*)的结果强转成Number
         Number n = (Number)obj;
         System.out.println(n.longValue());
     }

正文：JAVA中DBUtils的QueryRunner类实现增删改查详解 

 
一.QueryRunner类实现增删改  
public static void main(String[] args) throws Exception{ //使用自己的工具类，获取数据库的连接对象 

Connection conn = MyJDBCUtils.getConnection(); //创建QueryRunner类对象 
QueryRunner qr = new QueryRunner(); 
String sql = "UPDATE gjp_ledger set money=? , ldesc=? where lid=?"; 

Object[] params = {998,"买钻石",3}; 

int result = qr.update(conn, sql, params); 

System.out.println(result); DbUtils.close(conn);

 }  
二.QueryRunner类获取查询结果集ResultSetHandler    

 1.常用Handler  * ArrayHandler 将结果集第一行转成对象数组  
                    public static void main(String[] args) throws Exception{    

 Connection conn = MyJDBCUtils.getConnection();    

 String sql = "SELECT * FROM gjp_ledger where lid=?";     //结果集处理方式，ArrayHandler 第一行转成对象数组  

   QueryRunner qr = new QueryRunner(); 
    Object[] objects = qr.query(conn, sql, new ArrayHandler(),3);  

   for(Object obj : objects){    

 System.out.println(obj);   

  }    

 }  
* ArrayListHandler 将结果集中的每一行数据都转成一个对象数组，再将转成的多个对象数组存放到List中  
public static void main(String[] args) throws Exception{     

 Connection conn = MyJDBCUtils.getConnection(); 

String sql = "SELECT * FROM gjp_ledger";

 QueryRunner qr = new QueryRunner(); 
//执行query方法，传递连接对象，SQL语句，结果集处理方式ArrayListHandler 

List list = qr.query(conn, sql, new ArrayListHandler());

 for(Object[] objects : list)

{ for(Object obj : objects){ 

System.out.print(obj+" "); 

} 
System.out.println(); 

}

 }  
* BeanHandler 将结果集第一行数据封装到一个对应的业务类实例中  (1): 定义业务数据类Ledger(实体类，javaBean) 

public class Ledger { 
//要生成空参、有参构造、set和get方法、toString方法 

private int lid; 

private String parent; 

private double money; 

private int sid;

 private String account; 

private String createtime;

 private String ldesc; 

 } 
 (2)测试案例代码 
public static void main(String[] args) throws Exception{

Connection conn = MyJDBCUtils.getConnection(); 

String sql = "SELECT * FROM gjp_ledger";

 QueryRunner qr = new QueryRunner(); 
//BeanHandler泛型 ，构造方法(和反射有关系的对象) 
Ledger legder = qr.query(conn, sql, new BeanHandler(Ledger.class));

 System.out.println(legder);

 }  
* BeanListHandler 将结果集中的每一行数据都封装到一个对应的业务类实例中，再将多个业务类实例对象存放到List里。  
public static void main(String[] args) throws Exception {

Connection conn = MyJDBCUtils.getConnection(); 

String sql = "SELECT * FROM gjp_ledger"; 
//结果集处理方式，BeanListHandler 每一行数据封装到业务数据类中

QueryRunner qr = new QueryRunner(); 
List list = qr.query(conn, sql, new BeanListHandler(Ledger.class)); 

for(Ledger ledger : list)

{ 

System.out.println(ledger);

 } 

}  
* MapHandler 将结果集中的第一行数据封装到一个Map中，key是列名，value是对应的值。  
public static void main(String[] args) throws Exception {

Connection conn = MyJDBCUtils.getConnection(); 

String sql = "SELECT * FROM gjp_ledger"; 
//结果集处理方式，MapHandler 封装到一个Map集合中，存储键值对集合

QueryRunner qr = new QueryRunner(); 
Map map = qr.query(conn, sql,new MapHandler()); 

for(String key : map.keySet()){ 
System.out.println(key+"  "+map.get(key));

 }

 }  
* MapListHandler 将结果集中的每一行数据都封装到一个Map里，然后再将多个Map存放到List  
public static void main(String[] args) throws Exception{

Connection conn = MyJDBCUtils.getConnection(); 

String sql = "SELECT * FROM gjp_ledger"; 
//结果集处理方式，MapListHandler 数据中的每一行封装成Map集合，多个Map集合存储到List集合 
QueryRunner qr = new QueryRunner(); 
List> list = qr.query(conn, sql,new MapListHandler()); 

for(Map map : list){ 

for(String key : map.keySet()){ 
System.out.print(key+" "+map.get(key)); 

} 
System.out.println();
}

 }  

 *  ColumnListHandler                     将结果集中某一列的数据存放到List中  
public static void main(String[] args)throws Exception {     

Connection conn = MyJDBCUtils.getConnection(); 

String sql = "SELECT * FROM gjp_ledger"; 
//结果集处理方式，ColumnListHandler 数据中一个列，数据存储到List集合 

QueryRunner qr = new QueryRunner(); //ColumnListHandler构造方法中，写字符串列名 
List list = qr.query(conn, sql,new ColumnListHandler("money"));

 for(Double money : list){ System.out.println(money);

 }

 }  
* ScalarHandler 进行单值查询,如：select count(*) from                                  
 public static void main(String[] args) throws Exception{ 

Connection conn = MyJDBCUtils.getConnection(); 

String sql = "SELECT count(*)as count FROM gjp_ledger"; //结果集处理方式，ScalarHandler 满足只有1列，1个数据 

QueryRunner qr = new QueryRunner(); //ColumnListHandler构造方法中，写字符串列名 
Long i = qr.query(conn, sql, new ScalarHandler("count"));

 System.out.println(i);

 }   
 * KeyedHandler将结果集中的每一行数据都封装为一个Map(List

Connection conn = MyJDBCUtils.getConnection(); 

String sql = "SELECT *  FROM gjp_ledger"; //结果集处理方式，KeyedHandler 

QueryRunner qr = new QueryRunner(); 

Map > map= qr.query(conn, sql, new KeyedHandler("lid")); 

System.out.println(map); 

}