Mybatis之分页插件pagehelper的简单使用

最近从家里回来之后一直在想着减肥的事情,一个月都没更新博客了,今天下午没睡午觉就想着把mybatis的分页插件了解一下,由于上个月重新恢复了系统,之前创建的项目都没了,又重新创建了一个项目。

一、创建maven项目

主要创建了User类、UserMapper.xml、database.properties、mybatis-config.xml。

Mybatis之分页插件pagehelper的简单使用

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">
<!-- 为这个mapper指定一个唯一的namespace,namespace的值习惯上设置成包名+sql映射文件名,这样就能够保证namespace的值是唯一的
例如namespace="Cuiyw.MyBatis.DBMapping.UserMapper"就是Cuiyw.MyBatis.DBMapping(包名)+UserMapper(UserMapper.xml文件去除后缀)
-->
<mapper namespace="Cuiyw.MyBatis.DBMapping.UserMapper">
<!-- 在select标签中编写查询的SQL语句, 设置select标签的id属性为getUser,id属性值必须是唯一的,不能够重复
使用parameterType属性指明查询时使用的参数类型,resultType属性指明查询返回的结果集类型
resultType="Cuiyw.MyBatis.Model.User"就表示将查询结果封装成一个User类的对象返回
User类就是user表所对应的实体类
-->
<!--
根据id查询得到一个user对象
-->
<select id="getUser" parameterType="int"
resultType="Cuiyw.MyBatis.Model.User">
select * from user where id=#{id}
</select>
<select id="getUserList" resultType="Cuiyw.MyBatis.Model.User">
select * from user
</select>
<insert id="addUser" parameterType="Cuiyw.MyBatis.Model.User">
<selectKey resultType="java.lang.Integer" order="AFTER" keyProperty="id">
SELECT LAST_INSERT_ID()
</selectKey>
insert into user(name,age) values (#{name},#{age})
</insert>
<delete id="deleteUserById" parameterType="int">
delete from user where id=#{id}
</delete>
<update id="updateUser" parameterType="Cuiyw.MyBatis.Model.User">
update user set name=#{name},age=#{age} where id=#{id}
</update>
</mapper>

User类

package Cuiyw.MyBatis.Model;

public class User {
@Override
public String toString() {
// TODO Auto-generated method stub
return "User [id=" + Id + ", name=" + Name + ", age=" + Age + "]"; }
public int getId() {
return Id;
}
public void setId(int id) {
Id = id;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public int getAge() {
return Age;
}
public void setAge(int age) {
Age = age;
}
private int Id;
private String Name;
private int Age;
}

database.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis

mybatis-config.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>
<properties resource="database.properties">
<property name="username" value="root"/>
<property name="password" value="123456"/>
</properties>
<typeAliases>
<typeAlias type="Cuiyw.MyBatis.Model.User" alias="User"/>
</typeAliases>
<plugins>
<!-- com.github.pagehelper为PageHelper类所在包名 -->
<plugin interceptor="com.github.pagehelper.PageHelper">
<!-- 方言 -->
<property name="dialect" value="mysql"/>
<!-- 该参数默认为false -->
<!-- 设置为true时,使用RowBounds分页会进行count查询 -->
<property name="rowBoundsWithCount" value="true"/>
</plugin>
</plugins>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<!-- 配置数据库连接信息 -->
<dataSource type="POOLED">
<property name="driver" value="${driver}" />
<property name="url" value="${url}" />
<property name="username" value="${username}" />
<property name="password" value="${password}" />
</dataSource>
</environment>
</environments> <!-- 程序中所用到sql映射文件都在这里列出,这些映射sql都被Mybatis管理 -->
<mappers>
<mapper resource="Cuiyw/MyBatis/DBMapping/UserMapper.xml" />
</mappers> </configuration>

二、pagehelper插件的配置

pom.xml配置

除了上面mybatis-config.xml中配置的plugin插件com.github.pagehelper.PageHelper.这里还主要使用了org.mybatis、mysql、com.github.pagehelper、com.github.jsqlparser,分页插件的是后面两个。

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion> <groupId>Cuiyw</groupId>
<artifactId>MyBatisDemo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging> <name>MyBatisDemo</name>
<url>http://maven.apache.org</url> <properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.2.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>
</dependency>
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper</artifactId>
<version>3.4.2</version>
</dependency>
<dependency>
<groupId>com.github.jsqlparser</groupId>
<artifactId>jsqlparser</artifactId>
<version>0.9.1</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>

三、数据库配置

这里我事先在user表准备了一个几条数据。

Mybatis之分页插件pagehelper的简单使用

四、插件的使用

PageHelper.startPage(1, 5, true)用来设置分页,PageInfo用来显示分页信息。

package Cuiyw.MyBatisDemo;
import java.io.IOException;
import java.io.Reader;
import java.util.List;
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 com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo; import Cuiyw.MyBatis.Model.User; public class App
{
public static void main( String[] args ) throws IOException
{
//mybatis的配置文件
String resource = "mybatis-config.xml";
//使用MyBatis提供的Resources类加载mybatis的配置文件(它也加载关联的映射文件)
Reader reader = Resources.getResourceAsReader(resource);
//构建sqlSession的工厂
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
//创建能执行映射文件中sql的sqlSession
SqlSession session = sessionFactory.openSession(); // String statement="Cuiyw.MyBatis.DBMapping.UserMapper.addUser";
// User user=new User();
// user.setName("Cuiyw");
// user.setAge(27);
// int result=session.insert(statement, user);
// session.commit();
// session.close();
// System.out.println(user.getId());
System.out.println("------所有记录----------");
String statement="Cuiyw.MyBatis.DBMapping.UserMapper.getUserList";
List<User>users=session.selectList(statement);
for (User u: users) {
System.out.println(u.toString());
}
System.out.println("------分页----------");
PageHelper.startPage(1, 5, true);
statement="Cuiyw.MyBatis.DBMapping.UserMapper.getUserList";
users=session.selectList(statement);
for (User u: users) {
System.out.println(u.toString());
} PageInfo<User> pageInfo = new PageInfo<User>(users);
System.out.println("数据总数:" + pageInfo.getTotal());
System.out.println("数据总页数:" + pageInfo.getPages());
System.out.println("最后一页:" + pageInfo.getLastPage()); for (User u: pageInfo.getList()) {
System.out.println(u.toString());
}
}
}

Mybatis之分页插件pagehelper的简单使用

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