02-使用C3P0连接池连接MySql并且使用QueryRunner简化数据库操作

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/grain</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="user">root</property>
<property name="password">123</property>

<property name="acquireIncrement">3</property>
<property name="initialPoolSize">10</property>
<property name="minPoolSize">2</property>
<property name="maxPoolSize">10</property>
</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<T> 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<T> 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>(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<User> list_u = q.query(sql, new BeanListHandler<User>(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<String,Object> map_u = q.query(sql, new MapHandler(),"0001");
System.out.println(map_u);
}
//多行结果集，List<map>
@Test
public void testQuery4() throws SQLException{
String sql = "select * from user_info";
QueryRunner q = new TxQueryRunner();
List<Map<String,Object>> 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());
}