MyBatis Basic Learning (II.)-Developing DAO Way

First, the original DAO development Way

Userdao.java

public interface Userdao{public User Finduserbyid (Serializable id);p ublic list<user> findusersbyname (String name );}

Userdaoimpl.java

The public class Userdaoimpl implements Userdao{//sqlsessionfactory is a singleton that should not be created in a specific instance and requires an external dependency injected into the private sqlsessionfactory Sqlsessionfactory;public Userdaoimpl (sqlsessionfactory sqlsessionfactory) {this.sqlsessionfactory = Sqlsessionfactory;} @Overridepublic User Finduserbyid (Serializable id) {sqlsession sqlsession = sqlsessionfactory.opensession (); User user = Sqlsession.selectone ("Test.finduserbyid", id); Sqlsession.close (); return user;} @Overridepublic list<user> findusersbyname (String name) {sqlsession sqlsession = sqlsessionfactory.opensession ( ); list<user> list = sqlsession.selectlist ("Test.finduserbyname", name); Sqlsession.close (); return list;}}

Test.java

public class Userdaotest{private Sqlsessionfactory sqlsessionfactory;private Userdao userdao;{ String resource = "Sqlmapconfig.xml"; InputStream is;try{is = Resources.getresourceasstream (Resource); Sqlsessionfactorybuilder builder = new Sqlsessionfactorybuilder (); sqlsessionfactory = Builder.build (is); UserDao = new Userdaoimpl (sqlsessionfactory);} catch (IOException e) {e.printstacktrace ();}} @Testpublic void Testfinduserbyid () {User user = Userdao.finduserbyid (27); SYSTEM.OUT.PRINTLN (user);} @Testpublic void Testfindusersbyname () {list<user> List = Userdao.findusersbyname ("Xiaoming"); for (User user:list) { SYSTEM.OUT.PRINTLN (user);}}}

There are some problems with the original DAO Development:

(1) There is a certain amount of template code

For example: Create sqlsession through Sqlsessionfactory, invoke Sqlsession method to manipulate database, close sqlsession.

(2) There are some hard-coded

When you invoke the Sqlsession method to manipulate the database, you need to specify the ID of the statement, which is hard-coded.

Second, mapper agent development mode

Mapper Agent development method, programmers only need to write the Mapper interface (equivalent to DAO interface) can be. MyBatis automatically generates a dynamic proxy implementation class for the Mapper interface. However, to implement the Mapper agent development method, we need to follow some development specifications.

(1) The fully qualified name of the Mapper interface is the same as the value of namespace for the mapper mapping file .
(2) The method name of the Mapper interface is the same as the ID of the statement in the mapper mapping file .
(3) The method parameter of the Mapper interface can only have one, and the type is consistent with the value of ParameterType statement in the mapper mapping file.
(4) The return value type of the Mapper interface should be consistent with the Resulttype value in the Mapper mapping file or the type value in RESULTMAP statement.

Mapper.java

Public interface Usermapper{public user Finduserbyid (int id);p ublic void saveuser (user user);

Usermapper.xml

<?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 "><!--namespace: At this time with the Mapper proxy mode, its value must be equal to the fully qualified name of the corresponding mapper interface -<Mappernamespace= "Com.kiwi.mapper.UserMapper">    <!--query a user by ID -    <SelectID= "Finduserbyid"ParameterType= "int"Resulttype= "Com.kiwi.domain.User">SELECT * from USER WHERE id = #{id}</Select>        <!--fuzzy query by name -    <SelectID= "Finduserbyname"ParameterType= "Java.lang.String"Resulttype= "Com.kiwi.domain.User">SELECT * from USER WHERE username like '%${value}% '</Select>        <!--add a user and return the inserted ID -    <InsertID= "Saveuser"ParameterType= "Com.kiwi.domain.User">        <SelectkeyKeyproperty= "id"Resulttype= "int"Order= "after">SELECT last_insert_id ()</Selectkey>INSERT into USER (username,birthday,sex,address) VALUES (#{username},#{birthday},#{sex},#{address})</Insert>        <!--Delete a user -    <DeleteID= "DeleteUser"ParameterType= "int">DELETE from USER WHERE id = #{id}</Delete>        <!--Modify a user -    <UpdateID= "UpdateUser"ParameterType= "Com.kiwi.domain.User">UPDATE USER SET username = #{username},address = #{address} WHERE id = #{id}</Update></Mapper>

Sqlmapconfig.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>    <!--Configure the MyBatis environment information, which, when integrated with spring, will be managed by spring -    <Environmentsdefault= "Development">        <EnvironmentID= "Development">            <!--Configuring JDBC Transaction control, managed by MyBatis -            <TransactionManagertype= "JDBC"></TransactionManager>            <!--Configure the data source with DBCP connection pool -            <DataSourcetype= "Pooled">                < Propertyname= "Driver"value= "Com.mysql.jdbc.Driver" />                < Propertyname= "url"value= "Jdbc:mysql://localhost:3306/mybatis?useunicode=true&amp;characterencoding=utf8" />                < Propertyname= "username"value= "root" />                < Propertyname= "Password"value= "123456" />            </DataSource>        </Environment>    </Environments>    <!--Load Mapper -    <mappers>        <MapperResource= "Mapper/usermapper.xml"/>    </mappers></Configuration>

Test.java

Private sqlsessionfactory sqlsessionfactory; @Beforepublic void SetUp () throws Exception{inputstream InputStream = Resources.getresourceasstream ("Sqlmapconfig.xml"); sqlsessionfactory = new Sqlsessionfactorybuilder (). Build ( InputStream);} @Testpublic void Testfinduserbyid () {sqlsession sqlsession = sqlsessionfactory.opensession (); Usermapper mapper = Sqlsession.getmapper (Usermapper.class); User user = Mapper.finduserbyid (26); SYSTEM.OUT.PRINTLN (user); Sqlsession.close ();} @Testpublic void Testsaveuser () {sqlsession sqlsession = sqlsessionfactory.opensession (); Usermapper mapper = Sqlsession.getmapper (Usermapper.class); User user = New User ("WWW", "1", New Date (), "Haidian District, Beijing"); Mapper.saveuser (user); SYSTEM.OUT.PRINTLN (user); Sqlsession.commit (); Sqlsession.close ();}}

Third, global configuration 1.properties

2.typeAliases

Category name, only the type alias definition of the PO class.

Alias	Types of mappings
_byte	Byte
_long	Long
_short	Short
_int	Int
_integer	Int
_double	Double
_float	Float
_boolean	Boolean
String	String
Byte	Byte
Long	Long
Short	Short
Int	Integer
Integer	Integer
Double	Double
Float	Float
Boolean	Boolean
Date	Date
Decimal	BigDecimal
BigDecimal	BigDecimal

MyBatis Basic Learning (II.)-Developing DAO Way