01_ querying user data by ID

"Engineering Catalog"

"Database table content User table"

"Sqlmapconfig.xml configuration file main content"

Description: The Sqlmapconfig.xml configuration file has two main functions:

1. Information about configuration and data connections, such as transaction management, database connection pooling, and so on.

2. Load the mapping file, such as User.xml in this project

1 <?XML version= "1.0" encoding= "UTF-8"?>2 <!DOCTYPE  configuration  3 Public "-//mybatis.org//dtd Config 3.0//en"4 "Http://mybatis.org/dtd/mybatis-3-config.dtd">5 <Configuration>6     7     <!--after integration with spring, these configurations will be removed -8     <Environmentsdefault= "Development">9         <EnvironmentID= "Development">Ten             <!--using JDBC Transaction management - One             <TransactionManagertype= "JDBC" /> A             <!--Database Connection Pool - -             <DataSourcetype= "Pooled"> -                 < Propertyname= "Driver"value= "Com.mysql.jdbc.Driver"/> the                 < Propertyname= "url"  - value= "Jdbc:mysql://localhost:3306/mybatisdb? useunicode=true&amp;characterencoding=utf-8"  /> -                 < Propertyname= "username"value= "root"/> -                 < Propertyname= "Password"value=""/> +             </DataSource> -         </Environment> +     </Environments> A      at     <!--Load Map File - -     <mappers> -         <MapperResource= "Sqlmap/user.xml"/> -     </mappers> -      - </Configuration>

"User.xml"

Write the associated crud code in the User.xml file

<?XML version= "1.0" encoding= "UTF-8"?><!DOCTYPE Mapper Public "-//mybatis.org//dtd mapper 3.0//en" "Http://mybatis.org/dtd/mybatis-3-mapper.dtd "><Mappernamespace= "Test">    <SelectID= "Finduserbyid"ParameterType= "int"Resulttype= "com. Higgin.Mybatis.po.User ">SELECT * from USER WHERE Id=#{id}</Select></Mapper>

Explain:

1.namespace namespaces, the role is to classify the SQL management. Note: namespace has a special role to play with Mapper proxy method development.

2. Many SQL statements can be configured in the <mapper> mapping file, except <select> <delete>, <update>, <insert>, etc.

3. Perform a database query through select, encapsulate the SQL statement into the Mapperstatement object, so ID becomes the ID of the statement

4.parameterType: Specifies the type of input parameter, specified here is the int type

5.#{}: Represents a placeholder

6.#{id}: Where the placeholder represents the access input parameters, parameter name is called ID, if the input parameter is a simple type, #{} parameter name can be arbitrary, can be value or other name

7.resultType: Specifies the Java type object to which the SQL output results are mapped, andselect specifies that the Resulttype represents a user object that maps a single record

"Log4j.properties"

#Global Logging configuration# in the development environment, the log level is set to DEBUGlog4j.rootlogger=debug,stdout#Console Output ... log4j.appender.stdout=org.apache.log4j.ConsoleAppenderlog4j.appender.stdout.layout=  Org.apache.log4j.PatternLayoutlog4j.appender.stdout.layout.conversionpattern=%5p [%t]-%m%n

"User.java"

1  Packagecom. Higgin.Mybatis.po;2 3 Importjava.util.Date;4 5  Public classUser {6     //property name corresponds to database table field7         Private intID;8         PrivateString username;9         PrivateString sex;Ten         PrivateDate birthday; One         PrivateString address; A        //ignore get, set, tostring method .... -}

"Mybatistest.java"

 Public classmybatistest {@Test Public voidTestfinduserbyid ()throwsioexception{//mybatis configuration fileString resource= "Sqlmapconfig.xml"; //Get configuration fileInputStream inputstream=Resources.getresourceasstream (Resource); //creating a session factory, passing in MyBatis profile informationSqlsessionfactory sqlsessionfactory=NewSqlsessionfactorybuilder (). Build (InputStream); //get sqlsession through the factorySqlsession sqlsession=sqlsessionfactory.opensession (); //manipulating databases with sqlsession//First parameter: The ID of the statement in the mapping file, equal to: namespace+ "." ID of the +statement//second parameter: Specify the parameters of the matching parametertype type in the mapping fileUser User=sqlsession.selectone ("Test.finduserbyid", 2);        System.out.println (User.tostring ()); //Freeing ResourcesSqlsession.close (); }}

"Run Results"

01_ querying user data by ID