• 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。

    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>
    View Code

    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; 
    }
    View Code

    database.properties

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

    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>
    View Code

    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>
    View Code

    三、数据库配置

    这里我事先在user表准备了一个几条数据。

    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());  
            } 
        }
    }
    View Code

  • 相关阅读:
    PHP WEB项目文件夹上传下载解决方案
    .NET WEB项目文件夹上传下载解决方案
    C#.NET WEB项目文件夹上传下载解决方案
    python 多重继承
    python 多态
    python 类型判断-- isinstance函数
    python 继承
    hdu 5692 Snacks 线段树+dfs
    线段树的输出
    python 定义类方法
  • 原文地址:https://www.cnblogs.com/5ishare/p/8639374.html
Copyright © 2020-2023  润新知