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This article introduces the example analysis of Spring and MyBatis, the content is very detailed, interested friends can refer to, hope to be helpful to you.

Reference:

Mybatis initialization process and its important classes

Introduction and Application of SqlSessionFactory and SqlSession

SqlSessionFactoryBean source code parsing

The difference between @ Mapper and @ MapperScan

Spring integrates Mybatis principle

The use of JDBC in Java

The steps to use JDBC include

Set the database's url, user name, password and other constants

Load the driver class, such as MySQL's com.mysql.cj.jdbc.Driver.

This driver class static code block java.sql.DriverManager.registerDriver (new Driver ()); is executed when com.mysql.cj.jdbc.Driver is loaded, registering the driver with DriverManager

Create a Connection object using Driver or DriverManager

Use Connection objects to control whether transactions are automatically committed, manually committed, rolled back, or created Statement objects to execute sql statements

Initialization and simple use of MyBatisMyBatis

The following code completes loading the xml configuration file of mybatis into the Conguration object, creating the SqlSessionFactory object, creating the SqlSession object, and calling the method in the specified mapper to complete a database query

String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream (resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder () .build (inputStream); SqlSession sqlSession = sqlSessionFactory.openSession (); List list = sqlSession.selectList ("com.foo.bean.BlogMapper.queryAllBlogInfo")

The structure of the Configuration class corresponds to the structure of mybatis's xml configuration file.

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder () .build (inputStream)

Public SqlSessionFactory build (InputStream inputStream, String environment, Properties properties) {try {/ / this object is used to parse XMLConfigBuilder parser = new XMLConfigBuilder (inputStream, environment, properties); / / parser.parse () implements parsing the xml configuration file of mybatis to the Configuration object in Java, and returns this object return build (parser.parse ()) } catch (Exception e) {throw...} finally {ErrorContext.instance (). Reset (); try {inputStream.close ();} catch (IOException e) {/ / Intentionally ignore. Prefer previous error. Create and return a DefaultSqlSessionFactory object public SqlSessionFactory build (Configuration config) {return new DefaultSqlSessionFactory (config);}

In the above process of using mybatis, the process of parsing the mybatis configuration file is encapsulated inside the SqlSessionFactoryBuilder.build () method

We can also use the overloaded method to pass the Configuration object as a parameter to the build method and explicitly parse the configuration file

String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream (resource); / / create XMLConfigBuilder manually and parse to create Configuration objects XMLConfigBuilder parser = new XMLConfigBuilder (inputStream, null,null); Configuration configuration=parse (); / / use Configuration objects to create SqlSessionFactorySqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder (). Build (configuration); / / use MyBatisSqlSession sqlSession = sqlSessionFactory.openSession (); List list = sqlSession.selectList ("com.foo.bean.BlogMapper.queryAllBlogInfo"); SqlSessionFactory

The role of SqlSessionFactory

SqlSessionFactory is a compiled memory mirror of a single database mapping relationship. Every MyBatis application centers on an instance of a SqlSessionFactory object. SqlSessionFactory provides methods for creating SqlSession objects

How SqlSessionFactory is created

New an object directly and configure the required Configuration object for it

Created with the build () method of SqlSessionFactoryBuilder. This method is overloaded many times, and its core is to parse the xml file of mybatis into a Configuration object, based on which a SqlSessionFactory object is created.

Thread Safety of SqlSessionFactory

SqlSessionFactory is thread-safe, and once SqlSessionFactory is created, it should exist during the execution of the application. Do not create it repeatedly during the running of the application. It is recommended to use singleton mode. SqlSessionFactory is the factory for creating SqlSession.

SqlSession

The role of SqlSession

SqlSession is the object that performs the persistence operation. Similar to Connection in JDBC.

The realization of SqlSession

The SqlSession interface provides CURD methods and methods for managing transactions and obtaining mapper proxy objects, which encapsulates JDBC at the underlying layer

Thread Safety of SqlSession

It is a single-threaded object that performs interaction between the application and the persistence layer. Each thread should have its own instance of SqlSession. Instances of SqlSession cannot be shared, and SqlSession is not thread-safe

Spring integrates the working principle of MyBatis SqlSessionFactoryBean

The definition information for SqlSessionFactoryBean is often used like this

The SqlSessionFactoryBean class implements the InitializingBean interface. When its afterPropertiesSet () method is called, a SqlSessionFactory object is created and assigned to the member variable this.sqlSessionFactory

Spring IoC integrates MyBatis

This is how you use MyBatis in a Spring project

@ Componentpublic class UserService {@ Autowired private UserMapper userMapper; public User getUserById (Integer id) {return userMapper.selectById (id);}}

What we focus on is how Spring IoC instantiates and adds the interface UserMapper to the container.

Solution: (take UserMapper as an example) use FactoryBean to create an object for the UserMapper interface that declares that the type is UserMapper and the actual type is a dynamic proxy

And add objects to the container

But the custom XxxMapper is written by you, and it is uncertain. The framework does not create a XxxFactoryBean for each XxxMapper, so the FactoryBean holds a member variable that holds the type of object it is going to create. So as to create proxy objects of various Mapper classes.

In Spring's project to integrate MyBatis, this FactoryBean is MapperFactoryBean

Now there is another problem, each Mapper has to have a MapperFactoryBean. So where was MapperFactoryBean created?

Implemented by MapperFactoryBean and @ MapperScan

Import (MapperScannerRegistrar.class) public @ interface MapperScan {String [] basePackages () default {};...}

The purpose of @ MapperScan is to add a MapperScannerRegistrar object to the container and record the packages that need to be scanned

The XxxMapper under these packages will be scanned by MapperScannerRegistrar and a BeanDefinition object of type MapperFactoryFactoryBean will be created for it)

This is the end of the sample analysis on Spring and MyBatis. I hope the above content can be helpful to you and learn more knowledge. If you think the article is good, you can share it for more people to see.

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