Database connection pool and bdutils tool

One 、 Database connection pool

1、 What is a database connection pool

The database connection pool is responsible for allocation 、 Manage and release database connections , It allows applications to reuse an existing database connection , Instead of building a new ; Release database connection with idle time exceeding the maximum idle time to avoid missing database connection caused by no free database connection . This technology can obviously improve the performance of database operation .
principle
The basic idea of connection pool is to initialize the system , Store database connections as objects in memory , When the user needs to access the database , It's not about building a new connection , Instead, take an established free connection object out of the connection pool . After use , The user is not closing the connection , Instead, put the connection back in the connection pool , For next request access . And the establishment of connections 、 Disconnection is managed by the connection pool itself . meanwhile , You can also control the initial number of connections in the connection pool by setting the parameters of the connection pool 、 The number of connections and the maximum number of uses per connection 、 Maximum free time, etc . You can also monitor the number of database connections through its own management mechanism 、 Usage, etc .

2、DataSource Interface

As DriverManager An alternative to a tool ,DataSource An object is the preferred method to obtain a connection . Realization DataSource The object of the interface is usually based on JavaTM Naming and Directory Interface (JNDI) API Is registered in the naming service .

DataSource  The interface is implemented by the driver vendor . There are three types of implementations ：

 Basic implementation  -  Generating standard  Connection  object 
 Connection pool implementation  -  Generates a connection that automatically participates in the connection pool  Connection  object . This implementation is used with the mid-tier connection pool manager .
 Distributed transaction implementation  -  Generate a  Connection  object , This object can be used for distributed transactions , Always participate in connection pooling most of the time . This implementation is used with the mid-tier transaction manager , In most cases it is always used with the connection pool manager .

3.BDCP data source

DBCP rely on commons-pool Object pool , So we need to commons-dbcp.jar , commons-pool.jar
DBCP Of BasicDataSource Provides close（） Method , So again XML The configuration file needs to formulate destory-method=“close”, In order to Spring Close the data source normally .

Two 、BDUtile Tools

1.DButils Introduction to

To make it easier to use JDBC,Apache The organization provides DButils Tools , It is a database operation component , Realized with JDBC Simple encapsulation , Simplify without compromising performance JDBC The operation of . The latest version should be 1.7 Version of

2.QueryRunner An introduction to the

QueryRunner The use of classes is greatly simplified SQL Statement execution code , And ResultSetHandler Combination can complete various operations of the database ,QueryRunner Class provides   With parameters   Construction method of , This method uses javax.sql.DataSource Pass parameters to QueryRunner Get from the constructor of Connection object ,  also   For different database operations , There are different ways .
query（String sql ,ResultSetHandler rsh, Object … params）

 Query methods , The second one here   Parameter is ResultSetHandler  Interface , What you query is the result information , The request to return is JavaBean
, Generics are Bean class , Here, you need to establish an anonymous implementation class of the interface , rewrite handle And back to Bean object , It's OK to know that there is such a thing first , I'll explain it in detail when I look at the code ,
 there params It's a variable parameter , according to  SQL Statement to set parameters .

update（String sql, Object … params）

 Use and delete , Insert , Update database information , alike params It's a variable parameter .

3.ResultSetHandler Interface

ResultSetHandler The interface is used to handle RestultSet Result set , It can transform the data in the result set into different forms , Depending on the data type of the result ,ResultSetHandler Several common implementation classes are provided , As follows ：
BeanHander： The result set is distributed to JavaBean in , Save a piece of data .
BeanListHandler： Load each piece of data of the result into JavaBean In the example , Store in List, That is to save multiple pieces of data

4.QueryRunner Basic use of

 Add data 

public void testinsert() throws SQLException {
     ComboPooledDataSource
datasource = new ComboPooledDataSource(); QueryRunner queryrunner =
new QueryRunner(datasource); queryrunner.update(“insert into balance
values(?,?)”, “Bob”,192); }

 Update data 

public void testupdate() throws SQLException {
     QueryRunner
queryrunner = new QueryRunner(new ComboPooledDataSource());
queryrunner.update(“update balance set balance = ? where name = ?”,
8160, “Bob”); }

 Delete data 

public void testdelete() throws SQLException {
     QueryRunner
queryrunner = new QueryRunner(new ComboPooledDataSource());
queryrunner.update(“delete from balance where name=?”, “Bob”); }