MYBATIS basic operation

2018-01-23

MyBatis is an open source, lightweight, persistence framework. It automates the mapping between SQL databases and objects in Java. The mappings are decoupled from the application logic by packaging the SQL statements in XML configuration files.

configure the details of the database

<?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"/> 
			
         <dataSource type = "POOLED">
            <property name = "driver" value = "com.mysql.jdbc.Driver"/>
            <property name = "url" value = "jdbc:mysql://localhost:3306/details"/>
            <property name = "username" value = "root"/>
            <property name = "password" value = "password"/>
         </dataSource>   
         
      </environment>
   </environments>
	
   <mappers>
      <mapper resource = "mybatis/Student.xml"/>
   </mappers>
   
</configuration>

The POJO class

public class Student {
   private int id;
   private String name;
   private String branch;
   private int percentage;
   private int phone;
   private String email;
   
   //Setters and getters   
}

Mapped Statements

Mapped SQL statements are resided within the element named . This element contains an attribute called ‘namespace’:

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<mapper namespace = "Student">
   //mapped statements and result maps
<mapper>

id is unique identifier used to identify the insert statement. On the other hand, parametertype is the class name or the alias of the parameter that will be passed into the statement:

<insert id = "insert" parameterType = "Student">
   INSERT INTO STUDENT1 (NAME, BRANCH, PERCENTAGE, PHONE, EMAIL ) 
   VALUES (#{name}, #{branch}, #{percentage}, #{phone}, #{email});    
</insert>
<update id = "update" parameterType = "Student">
   UPDATE STUDENT SET EMAIL = #{email}, NAME = #{name}, BRANCH = #{branch}, PERCENTAGE = #{percentage}, PHONE = #{phone} WHERE ID = #{id};
</update>
<delete id = "deleteById" parameterType = "int">
   DELETE from STUDENT WHERE ID = #{id};
</delete>

invoke the ‘insert’ mapped query:

//Assume session is an SqlSession object.  
session.insert("Student.insert", student);
session.update("Student.update",student);
session.delete("Student.deleteById", 18);

resultMaps

maps the results of the select queries to the Student class

<resultMap id = "result" type = "Student">
   <result property = "id" column = "ID"/>
   <result property = "name" column = "NAME"/>
   <result property = "branch" column = "BRANCH"/>
   <result property = "percentage" column = "PERCENTAGE"/>
   <result property = "phone" column = "PHONE"/>
   <result property = "email" column = "EMAIL"/>
</resultMap>
<select id = "getAll" resultMap = "result">
   SELECT * FROM STUDENT; 
</select>
<select id = "getById" parameterType = "int" resultMap = "result">
   SELECT * FROM STUDENT WHERE ID = #{id};
</select>

The method returns the data of the selected record in the form of List:

1	List<Student> list = session.selectList("Student.getAll");