Mybatis分页插件PageHelper的使用

PageHelper分页的实现利用了自定义拦截器实现了Mybatis拦截器接口。

1、pom.xml中引入pageHelper分页jar包

<!-- https://mvnrepository.com/artifact/com.github.pagehelper/pagehelper -->
    <dependency>
      <groupId>com.github.pagehelper</groupId>
      <artifactId>pagehelper</artifactId>
      <version>5.1.11</version>
    </dependency>

2、spring配置文件中配置分页插件

<!-- 把交给IOC管理 SqlSessionFactory -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!--配置mybatis 插件-->
        <property name="plugins">
            <set>
                <!--配置pageHelper 分页插件-->
                <bean class="com.github.pagehelper.PageInterceptor">
                    <property name="properties">
                        <props>
                            <!--方言：-->
                            <prop key="helperDialect">oracle</prop>
                        </props>
                    </property>
                </bean>
            </set>
        </property>
    </bean>

3、部分junit测试代码

    @Autowired
    private EmployeeService employeeService;

    @Test
    public void testPageHelper() {
        // 设置分页查询
        PageHelper.startPage(1, 3);
        List<Employee> empList = employeeService.getEmpByPage();
        for (Employee employee: empList) {
            System.out.println(employee);
        }
        // 此处输出的结果调用的PageHelper分页插件中Page类中重写的toString方法，其中Page类继承自ArrayList
        System.out.println(empList);
        PageInfo pageInfo = new PageInfo(empList);
        System.out.println(pageInfo);
    }

其中需要注意的是Page类继承自ArrayList，其中重写了toString()方法

 重写的toString()方法

public String toString() {
        return "Page{count=" + this.count + ", pageNum=" + this.pageNum + ", pageSize=" + this.pageSize + ", startRow=" + this.startRow + ", endRow=" + this.endRow + ", total=" + this.total + ", pages=" + this.pages + ", reasonable=" + this.reasonable + ", pageSizeZero=" + this.pageSizeZero + '}' + super.toString();
    }

例如上面junit测试代码中

System.out.println(empList)打印的结果如下

Page{count=true, pageNum=1, pageSize=3, startRow=0, endRow=3, total=14, pages=5, reasonable=false, pageSizeZero=false}[Employee{empno=7369, ename=SMITH, job=CLERK, mgr=7902, hiredate=Wed Dec 17 00:00:00 GMT+08:00 1980, sal=800.0, comm=0, deptno=20}, Employee{empno=7499, ename=ALLEN, job=SALESMAN, mgr=7698, hiredate=Fri Feb 20 00:00:00 GMT+08:00 1981, sal=1600.0, comm=300, deptno=30}, Employee{empno=7521, ename=WARD, job=SALESMAN, mgr=7698, hiredate=Sun Feb 22 00:00:00 GMT+08:00 1981, sal=1250.0, comm=500, deptno=30}]

PageInfo封装了结果集。如果需要取数据，可以利用该类中的对应方法。