【Mybatis】03：核心配置文件深入
第三章：MyBatis核心配置文件深入
OVERVIEW
- 第三章：MyBatis核心配置文件深入
-
-
- 一、MyBatis核心配置文件
-
- 1.typeHandlers标签
-
- （1）问题引出：
- （2）类型转换器实现：
- 2.plugins标签
-
- （1）问题引出：
- （2）分页操作：
-
一、MyBatis核心配置文件
1.typeHandlers标签
无论是MyBatis在预处理语句（PreparedStatement）中设置一个参数时，
还是从结果集中取出一个值时，都会用类型处理器将获取的值以合适的方式转换成Java类型：
如果要实现类型处理器处理不支持的或非标准的数据类型，这时就必须重写类型处理器，具体如下：
- 实现org.apache.ibatis.type.TypeHandler接口，或者继承一个很便利的类org.apache.ibatis.type.BaseTypeHandler
- 选择性的将其映射到一个JDBC类型
（1）问题引出：
例如，一个Java中的Date数据类型，要将其存储到数据库的时候保存为一个1970年至今的毫秒数，
而从数据库中取出时自动转换为Java的Date类型，这时要重写TypeHandler接口（即实现Date与数据库varchar毫秒值间的类型转换）
-
定义转换类继承BaseTypeHandler
，覆盖4个实现的方法，其中： setNonNullParameter为java程序设置数据到数据库的回调方法，
getNullableResult为查询时mysql字符串类型转换成java的Type类型的方法
-
在MyBatis核心配置文件中进行注册
-
测试转换是否正确
package com.itcast.domain;
import java.util.Date;
public class User {
private int id;
private String username;
private String password;
private Date birthday;
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassward() {
return password;
}
public void setPassward(String passward) {
this.password = passward;
}
/*方便测试与打印生成tostring方法*/
@Override
public java.lang.String toString() {
return "User{" + "id=" + id + ", username=" + username + ", passward=" + password + '}';
}
}
package com.itcast.mapper;
import com.itcast.domain.User;
public interface UserMapper {
public void save(User user);
}
DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itcast.mapper.UserMapper">
<insert id="save" parameterType="user">
insert into user value(#{id}, #{username}, #{password}, #{birthday})
insert>
mapper>
package com.itcast.test;
import com.itcast.domain.User;
import com.itcast.mapper.UserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
public class MapperTest {
@Test
public void test1() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
//mybatis实现dao层
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//1.模拟user
User user = new User();
user.setUsername("lch");
user.setPassward("abcde");
user.setBirthday(new Date());
//2.执行保存操作
mapper.save(user);
sqlSession.commit();
sqlSession.close();
}
}
（2）类型转换器实现：
- step1：定义转换类继承BaseTypeHandler
，覆盖4个实现的方法
package com.itcast.handler;
import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;
public class DateTypeHandler extends BaseTypeHandler<Date> {
//1.将java类型 转换成 数据库需要的类型
public void setNonNullParameter(PreparedStatement preparedStatement, int i, Date date, JdbcType jdbcType) throws SQLException {
Long time = date.getTime();
preparedStatement.setLong(i, time);
}
//2.将数据库中的类型 转换成java类型
/*
* String 要转换的字段名称
* ResultSet 查询出的结果集
**/
public Date getNullableResult(ResultSet resultSet, String s) throws SQLException {
//获取结果集中需要的数据long 转换为Date类型 返回
long aLong = resultSet.getLong(s);
Date date = new Date(aLong);
return date;
}
public Date getNullableResult(ResultSet resultSet, int i) throws SQLException {
long aLong = resultSet.getLong(i);
Date date = new Date(aLong);
return date;
}
public Date getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
long aLong = callableStatement.getLong(i);
Date date = new Date(aLong);
return date;
}
}
- step2：在MyBatis核心配置文件中进行注册
DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<typeHandlers>
<typeHandler handler="com.itcast.handler.DateTypeHandler">typeHandler>
typeHandlers>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC">transactionManager>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/test"/>
<property name="username" value="root"/>
<property name="password" value="20001201"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="com.itcast.mapper/UserMapper.xml">mapper>
mappers>
configuration>
- step3：测试
package com.itcast.test;
import com.itcast.domain.User;
import com.itcast.mapper.UserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
public class MapperTest {
@Test
public void test1() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
//mybatis实现dao层
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//1.模拟user
User user = new User();
user.setUsername("lch");
user.setPassward("abcde");
user.setBirthday(new Date());
//2.执行保存操作
mapper.save(user);
sqlSession.commit();
//3.执行查询操作
User result = mapper.findById(10);
System.out.println("user中的birthday：" + result.getBirthday());
sqlSession.close();
}
}
2.plugins标签
Mybatis可以使用第三方插件来对功能进行扩展，
Mybatis插件分页助手PageHelper，是将分页的复杂操作进行封装，使用简单的方式既可获得分页的相关数据。
实现步骤：
- 导入通用的PageHelper坐标
- 在mybatis核心配置文件中配置PageHelper插件
- 测试分页数据获取
（1）问题引出：
DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itcast.mapper.UserMapper">
<select id="findAll" resultType="com.itcast.domain.User">
select * from user
select>
mapper>
package com.itcast.mapper;
import com.itcast.domain.User;
import java.util.List;
public interface UserMapper {
public List<User> findAll();
}
package com.itcast.test;
import com.itcast.domain.User;
import com.itcast.mapper.UserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;
public class MapperTest {
@Test
public void test2() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//1.打印全部数据
List<User> userList = mapper.findAll();
for (User user : userList) {
System.out.println(user);
}
}
}
（2）分页操作：
- step1：pom文件导入plugin坐标
<dependency>
<groupId>com.github.pagehelpergroupId>
<artifactId>pagehelperartifactId>
<version>3.7.5version>
dependency>
<dependency>
<groupId>com.github.jsqlparsergroupId>
<artifactId>jsqlparserartifactId>
<version>0.9.1version>
dependency>
- step2：修改sqlMapConfig.xml文件，配置分页助手插件
DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<typeHandlers>
<typeHandler handler="com.itcast.handler.DateTypeHandler">typeHandler>
typeHandlers>
<plugins>
<plugin interceptor="com.github.pagehelper.PageHelper">
<property name="dialect" value="mysql"/>
plugin>
plugins>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC">transactionManager>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/test"/>
<property name="username" value="root"/>
<property name="password" value="20001201"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="com.itcast.mapper/UserMapper.xml">mapper>
mappers>
configuration>
- step3：测试分页数据获取
package com.itcast.test;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.itcast.domain.User;
import com.itcast.mapper.UserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;
public class MapperTest {
@Test
public void test2() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//1.设置分页相关参数 当前页 + 每页显示条数
PageHelper.startPage(2, 3);//查询第3-6条记录
//2.打印全部数据
List<User> userList = mapper.findAll();
for (User user : userList) {
System.out.println(user);
}
//3.获取与分页相关的参数
PageInfo<User> pageInfo = new PageInfo<User>(userList);
System.out.println("当前页：" + pageInfo.getPageNum());
System.out.println("每一页显示的条数：" + pageInfo.getPageSize());
System.out.println("总条数：" + pageInfo.getTotal());
System.out.println("总页数：" + pageInfo.getPages());
System.out.println("上一页：" + pageInfo.getPrePage());
System.out.println("下一页：" + pageInfo.getNextPage());
System.out.println("是否为第一页：" + pageInfo.isIsFirstPage());
System.out.println("是否为最后页：" + pageInfo.isIsLastPage());
}
}
