结合mybatis实现对pagehelper分页插件的简单使用。
一、创建一个maven项目并导入相关依赖
依赖文件：pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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>com.mgy</groupId>
<artifactId>Mybatis_10_pagehelper</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.1</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.16</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.13</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<!-- 分页插件的依赖 -->
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper</artifactId>
<version>5.0.0</version>
</dependency>
</dependencies>
</project>
二、创建一个操作实体：Employee.java
package com.mgy.mybatis.bean;
public class Employee {
private Integer id;
private String lastName;
private String email;
private String gender;
private EmpStatus empStatus = EmpStatus.LOGOUT;
public Employee() {
}
public Employee(String lastName, String email, String gender) {
this.lastName = lastName;
this.email = email;
this.gender = gender;
}
public EmpStatus getEmpStatus() {
return empStatus;
}
public void setEmpStatus(EmpStatus empStatus) {
this.empStatus = empStatus;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
@Override
public String toString() {
return "Employee{" +
"id=" + id +
", lastName='" + lastName + '\'' +
", email='" + email + '\'' +
", gender='" + gender + '\'' +
'}';
}
}
其他操作可能用到的枚举类：EmpStatus.java
package com.mgy.mybatis.bean;
/**
* @author MGY
* @data 2019/11/20 22:00
*/
public enum EmpStatus {
LOGIN,LOGOUT,REMOVE;
}
三、配置全局配置文件：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>
<typeHandlers>
<typeHandler handler="org.apache.ibatis.type.EnumOrdinalTypeHandler" javaType="com.mgy.mybatis.bean.EmpStatus" />
</typeHandlers>
<plugins>
<plugin interceptor="com.github.pagehelper.PageInterceptor"></plugin>
</plugins>
<environments default="dev_mysql">
<environment id="dev_mysql">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver" />
<property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis?allowMultiQueries = true&useUnicode=true&characterEncoding=UTF-8&userSSL=false&serverTimezone=GMT%2B8" />
<property name="username" value="root" />
<property name="password" value="root" />
</dataSource>
</environment>
<environment id="dev_oracle">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="oracle.jdbc.OracleDriver" />
<property name="url" value="jdbc:oracle:thin:@localhost:1521:orcl" />
<property name="username" value="scott" />
<property name="password" value="123456" />
</dataSource>
</environment>
</environments>
<!--
5、databaseIdProvider: 支持多数据库厂商的
type="DB_VENDOR": VendorDatabaseIdProvider
作用就是得到数据库厂商的标识（驱动 getDatabaseProductName()）
MySQL、Oracle、SQL Server ...
-->
<databaseIdProvider type="DB_VENDOR">
<!-- 为不同的数据库厂商起别名 -->
<property name="MySQL" value="mysql"/>
<property name="Oracle" value="oracle"/>
<property name="SQL Server" value="sqlserver"/>
</databaseIdProvider>
<!-- 将我们写好的sql映射文件（EmployeeMapper.xml）一定要注册到全局配置文件（mybatis-config.xml）中 -->
<mappers>
<mapper resource="EmployeeMapper.xml" />
</mappers>
</configuration>
四、配置一个日志配置文件，方便在控制台查看sql语句的操作：log4j.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
<appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
<param name="Encoding" value="UTF-8" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m (%F:%L) \n" />
</layout>
</appender>
<logger name="java.sql">
<level value="debug" />
</logger>
<logger name="org.apache.ibatis">
<level value="info" />
</logger>
<root>
<level value="debug" />
<appender-ref ref="STDOUT" />
</root>
</log4j:configuration>
五、创建一个操作数据库的持久类：EmployeeMapper.java
package com.mgy.mybatis.dao;
import com.mgy.mybatis.bean.Employee;
import java.util.List;
public interface EmployeeMapper {
Employee getEmpById(Integer id);
Long addEmps(Employee employee);
List<Employee> getMySQLEmployees();
List<Employee> getOracleEmployees();
}
六、配置持久类EmployeeMapper.java的mybatis的映射文件：EmployeeMapper.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: 名称空间；指定为接口的全类名
id: 唯一标识
resultType: 返回值类型
#{id}: 从传递过来的参数中取出 id 值
-->
<mapper namespace="com.mgy.mybatis.dao.EmployeeMapper">
<select id="getEmpById" resultType="com.mgy.mybatis.bean.Employee" >
select id, last_name lastName, email, gender from tbl_employee where id = #{id}
</select>
<!--Long addEmps(Employee employee);-->
<insert id="addEmps" useGeneratedKeys="true" keyProperty="id">
insert into tbl_employee(last_name, email, gender, empStatus)
values (#{lastName}, #{email}, #{gender}, #{empStatus})
</insert>
<!-- List<Employee> getMySQLEmployees(); -->
<select id="getMySQLEmployees" resultMap="PageEmp" databaseId="oracle">
select * from tbl_employee
</select>
<!-- List<Employee> getOracleEmployees(); -->
<select id="getOracleEmployees" resultMap="PageEmp" databaseId="oracle">
select * from employees
</select>
<resultMap id="PageEmp" type="com.mgy.mybatis.bean.Employee">
<id column="employee_id" property="id" />
<result column="last_name" property="lastName" />
<result column="email" property="email" />
<result column="gender" property="gender" />
</resultMap>
</mapper>
七、编写测试类：MyBatisTest.java
package com.mgy.mybatis.test;
import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.mgy.mybatis.bean.EmpStatus;
import com.mgy.mybatis.bean.Employee;
import com.mgy.mybatis.dao.EmployeeMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.ExecutorType;
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.List;
import java.util.UUID;
/**
* 1、接口式编程
* 原生： Dao ===========> DaoImpl
* mybatis: Mapper ===========> xxMapper.xml
* 2、SqlSession 代表和数据库的一次会话；用完必须关闭
* 3、SqlSession 和 connection 一样，它们都是非线程安全。每次使用都应该去获取新的对象
* 4、mapper 接口没有实现类，但是 mybatis 会为这个接口生成一个代理对象
* （将接口和 xml 进行绑定）
* EmployeeMapper empMapper = sqlSession.getMapper(EmployeeMapper.class);
* 5、两个重要的配置文件：
* mybatis 的全局配置文件：包含数据库连接池信息，事务处理器信息等....系统运行环境信息
* sql 映射文件：保存了每一个 sql 语句的映射信息：
* 将 sql 抽取出来
*/
public class MyBatisTest {
public SqlSessionFactory getSqlSessionFactory() throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
return new SqlSessionFactoryBuilder().build(inputStream);
}
/**
* 1、根据 xml 配置文件（全局配置文件）创建一个 SqlSessionFactory 对象 有数据源一些运行环境信息
* 2、sql 映射文件；配置了每一个 sql，以及 sql 的封装规则等。
* 3、将 sql 映射文件注册在全局配置文件中
* 4、写代码：
* 1）、根据全局配置文件得到 SqlSessionFactory
* 2）、使用 sqlSessionFactory 获取到 sqlSession 对象，使用它来执行增删改查
* 一个 sqlSession 就是代表和数据库的一次会话，用完关闭
* 3）、使用 sql 的唯一标识来告诉 MyBatis 执行哪个 sql。sql 都是保存在 sql 映射文件中的
* @throws IOException
*/
@Test
public void test() throws IOException {
// 2、获取sqlSession实例，能直接执行已经映射的sql语句
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
// selectOne 的参数
// 参数1 sql的唯一标识：statement Unique identifier matching the statement to use.
// 参数2 执行sql要用的参数：parameter A parameter object to pass to the statement.
Employee employee = sqlSession.selectOne("com.mgy.mybatis.dao.EmployeeMapper.getEmpById", 1);
System.out.println(employee);
} finally {
sqlSession.close();
}
}
@Test
public void test01() throws IOException {
// 1、获取 sqlSessionFactory 对象
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
// 2、获取 sqlSession 对象
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
// 3、获取接口的实现类对象
// MyBatis 会为接口自动的创建一个代理对象，代理对象去执行增删改查方法
EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
Employee empById = mapper.getEmpById(1);
System.out.println(mapper.getClass());
System.out.println(empById);
} finally {
sqlSession.close();
}
}
@Test
public void testBatch() throws IOException {
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
// 可以执行批量操作的 sqlSession
SqlSession sqlSession = sqlSessionFactory.openSession(ExecutorType.BATCH);
long start = System.currentTimeMillis();
try {
EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
for (int i = 0; i < 10000; i++) {
mapper.addEmps(new Employee(UUID.randomUUID().toString().substring(0, 5), "b", "1"));
}
sqlSession.commit();
long end = System.currentTimeMillis();
/*
* 批量：（预编译 sql 一次 ==> 设置参数 10000 次 ===> 执行一次） 执行时长：12394
* Parameters: 09c31(String), b(String), 1(String) (BaseJdbcLogger.java:145)
*
* 非批量： （预编译 sql = 设置参数 = 执行 = 10000 次） 执行时长：21923
* Preparing: insert into tbl_employee(last_name, email, gender) values (?, ?, ?) (BaseJdbcLogger.java:145)
* Parameters: 48154(String), b(String), 1(String) (BaseJdbcLogger.java:145)
* */
System.out.println("执行时长："+ (end - start));
} finally {
sqlSession.close();
}
}
/**
* MySQL 的测试
* @throws IOException
*/
@Test
public void testMySQLPageHelper() throws IOException {
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
Page<Object> page = PageHelper.startPage(1, 5);
List<Employee> employees = mapper.getMySQLEmployees();
for (Employee employee : employees) {
System.out.println(employee);
}
System.out.println("当前页码："+page.getPageNum());
System.out.println("总记录数："+page.getTotal());
System.out.println("每页的记录数："+page.getPageSize());
System.out.println("总页码："+page.getPages());
// 传入要连续显示多少页
PageInfo<Employee> info = new PageInfo<Employee>(employees, 5);
for (Employee employee : employees) {
System.out.println(employee);
}
///xxx
System.out.println("当前页码："+info.getPageNum());
System.out.println("总记录数："+info.getTotal());
System.out.println("每页的记录数："+info.getPageSize());
System.out.println("总页码："+info.getPages());
System.out.println("是否第一页："+info.isIsFirstPage());
System.out.println("连续显示的页码：");
int[] nums = info.getNavigatepageNums();
for (int i = 0; i < nums.length; i++) {
System.out.println(nums[i]);
}
} finally {
sqlSession.close();
}
}
/**
* Oracle 测试
* @throws IOException
*/
@Test
public void testOraclePageHelper() throws IOException {
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
Page<Object> page = PageHelper.startPage(1, 5);
List<Employee> employees = mapper.getOracleEmployees();
for (Employee employee : employees) {
System.out.println(employee);
}
System.out.println("当前页码："+page.getPageNum());
System.out.println("总记录数："+page.getTotal());
System.out.println("每页的记录数："+page.getPageSize());
System.out.println("总页码："+page.getPages());
// 传入要连续显示多少页
PageInfo<Employee> info = new PageInfo<Employee>(employees, 5);
for (Employee employee : employees) {
System.out.println(employee);
}
///xxx
System.out.println("当前页码："+info.getPageNum());
System.out.println("总记录数："+info.getTotal());
System.out.println("每页的记录数："+info.getPageSize());
System.out.println("总页码："+info.getPages());
System.out.println("是否第一页："+info.isIsFirstPage());
System.out.println("连续显示的页码：");
int[] nums = info.getNavigatepageNums();
for (int i = 0; i < nums.length; i++) {
System.out.println(nums[i]);
}
} finally {
sqlSession.close();
}
}
@Test
public void testEnumUse() {
EmpStatus login = EmpStatus.LOGIN;
System.out.println("枚举的索引："+login.ordinal());
System.out.println("枚举的名字："+login.name());
}
/**
* 默认 mybatis 在处理枚举对象的时候保存的是枚举的名字： EnumTypeHandler
* 改变使用：EnumOrdinalTypeHandler
* @throws IOException
*/
@Test
public void testEnum() throws IOException {
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
Employee employee = new Employee("test_enum", "enum@qq.com", "1");
mapper.addEmps(employee);
System.out.println("保存成功："+employee.getId());
sqlSession.commit();
} finally {
sqlSession.close();
}
}
}