Java framework --- Mybatis, java framework --- mybatis

Java framework --- Mybatis, java framework --- mybatis
1. Introduction to Mybatis

MyBatis is a first-class persistence framework that supports custom SQL, stored procedures, and advanced ing. MyBatis eliminates almost all JDBC code, and does not need to manually set parameters or obtain retrieval results. MyBatis can be configured in a simple XML format or annotation, and can Map basic data elements, Map interfaces, and POJOs (common java object) to records in the database.

Ii. MyBatis workflow (1) load configuration and initialize the trigger condition: the configuration file is loaded from two places, one is the configuration file and the other is the Java code annotation, load the SQL configuration information into MappedStatement objects (including input parameter ing configuration, executed SQL statements, and result ing configuration) and store them in the memory. (2) Receiving call request trigger condition: Call the API input parameters provided by Mybatis: SQL ID and input parameter object processing process: Pass the request to the lower request processing layer for processing. (3) processing operation request trigger condition: the API interface layer transmits the request to pass the input parameter: the SQL ID and the input parameter object processing process: () find the corresponding MappedStatement object based on the SQL ID. (B) parse the MappedStatement object based on the input parameter object to obtain the final SQL statement to be executed and execute the input parameter. (C) obtain the database connection, input parameters to the database for execution based on the obtained final SQL statement and execution, and obtain the execution result. (D) convert the execution result based on the result ing configuration in the MappedStatement object and obtain the final processing result. (E) release the connection resource. (4) return the processing result and return the final processing result. Basic Idea of orm tools

Either hibernate or mybatis, you can have one thing in common:

• Obtain sessionfactory from the configuration file (usually in the XML configuration file.
• Sessions generated by sessionfactory
• Add, delete, modify, and query data and commit transactions in the session.
• Close the session after it is used up.
• There is a mapping configuration file between the java object and the database, which is usually an xml file.

Functional Architecture

The functional architecture of Mybatis is divided into three layers:

Multiple driver packages to be added:

Below is a quick start:

The directory is as follows:

Entity User

package com.oumyye.model;public class User {    private String id;    private String name;    private  int age;    public String getId() {        return id;    }    public void setId(String id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    @Override    public String toString() {        return "User [id=" + id + ", name=" + name + ", age=" + age + "]";    }    }

Usering file UserMapping. xml

<? Xml version = "1.0" encoding = "UTF-8"?> <! DOCTYPE mapper PUBLIC "-// mybatis.org//DTD Mapper 3.0 //" http://mybatis.org/dtd/mybatis-3-mapper.dtd "> <mapper namespace =" com. oumyye. mapping. UserMapping "> <! -- Write the query SQL statement in the select tag and set the id attribute of the select tag to getUser. The id attribute value must be unique, the parameterType attribute cannot be used repeatedly to specify the parameter type used for query. The resultType attribute specifies the type of the returned result set in the query. resultType = "com. oumyye. model. "User" indicates that the query result is encapsulated into an object of the User class. The returned User class is the entity class corresponding to the users table --> <! -- Query by id to obtain a user object --> <select id = "getUser" parameterType = "String" resultType = "com. oumyye. model. user "> select * from user where id =#{ id} </select> </mapper>

Resource file mybatis. xml

<? Xml version = "1.0" encoding = "UTF-8"?> <! DOCTYPE configuration PUBLIC "-// mybatis.org//DTD Config 3.0 // EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <environments default = "development"> <environment id = "development"> <transactionManager type = "JDBC"/> <! -- Configure database connection information --> <dataSource type = "POOLED"> <property name = "driver" value = "com. mysql. jdbc. driver "/> <property name =" url "value =" jdbc: mysql: // localhost: 3306/mybatis "/> <property name =" username "value =" root "/> <property name =" password "value =" root "/> </dataSource> </ environment> </environments> <mappers> <mapper resource = "com/oumyye/mapping/userMapping. xml "/> </mappers> </configuration>

Test class:

Package test; import java. io. inputStream; import org. apache. ibatis. session. sqlSession; import org. apache. ibatis. session. sqlSessionFactory; import org. apache. ibatis. session. sqlSessionFactoryBuilder; import org. junit. test; import com. oumyye. model. user; public class Tests {@ Testpublic void test () {String resource = "mybatis. xml "; // use the class loader to load the configuration file of mybatis (It also loads the associated ing file) InputStream is = Tests. class. getClassLoader (). getResourceAsStream (resource); // The SqlSessionFactory sessionFactory that constructs the sqlSession = new SqlSessionFactoryBuilder (). build (is); SqlSession session = sessionFactory. openSession ();/*** ing the SQL identity string, * com. oumyye. mapping. userMapping is userMapper. the namespace attribute value of the ER er tag in the xml file. * getUser is the id attribute value of the select tag, you can find the SQL statement to be executed */String statement = "com. oumyye. mapping. userMapping. getUser "; // ing the SQL identity string // execute the query and return the SQL user User = session of a unique user object. selectOne (statement, "1123"); System. out. println (user. toString ());}}

Result: