Java學習之從入門到精通的Java分頁工具
阿新 • • 發佈：2021-11-09
從資料庫層面分頁(資料庫為MySQL，資料訪問層框架為MyBatis)
定義一個 PageBean 工具類。的工具類需要至少6個私有屬性，資料的totalRecord總數; totalPage 資料頁總數;pageSize：每頁幾個資料;pageNow 當前頁碼;列出當前頁碼的列表資料集合;startIndex sql 語句 查詢的起點。
package com . pagehelper . test ;
import java . util . List ;
public class PageBean < T > {
/*total number of records*/
private int totalRecord ;
/*total number of pages*/
private int totalPage ;
/*data per page Number of
items */private int pageSize ;
/*Current page number*/
private int pageNow ;
/*Data collection obtained<T>Generic in order to make the tool class universal*/
private List < T >list ;
/*Database query starts with that record*/
private int startIndex ;
public PageBean ( int pageNow , int pageSize , int totalRecord ) {
this . totalRecord = totalRecord ;
/*Trinocular operation, totalRecord can be divisible by pageSize totalPage=totalRecord/pageSize
* = Not divisible totalRecord TotalPage/* the pageSize +. 1/
TotalPage = totalRecord % the pageSize == 0 ? TotalRecord / the pageSize : totalRecord / the pageSize + . 1 ;
the this . The pageSize = the pageSize ;
the this . PageNow = pageNow ;
startIndex = ( pageNow - . 1 ) * pageSize ;
}
/*Constructor for fixed PageSize*/
public PageBean( int pageNow , int totalRecord ) {
this . totalRecord = totalRecord ;
pageSize = 5 ;
totalPage = totalRecord % pageSize == 0 ? totalRecord / pageSize : totalRecord / pageSize + 1 ;
this . pageNow = pageNow ;
startIndex = ( pageNow - 1) * pageSize ;
}
/*Set,Get method*/
public int getTotalRecord ( ) {
return totalRecord ;
}
public void setTotalRecord ( int totalRecord ) {
this . totalRecord = totalRecord ;
}
public int getTotalPage ( ) {
return totalPage ;
}
public void setTotalPage ( int totalPage ) {
this . totalPage = totalPage ;
}
public int getPageSize ( ) {
return pageSize ;
}
public void setPageSize ( int pageSize ) {
this . pageSize = pageSize ;
}
public int getPageNow ( ) {
return pageNow ;
}
public void setPageNow ( int pageNow ) {
this . pageNow = pageNow ;
}
public List < T > getList ( ) {
return list ;
}
public void setList ( List < T > list ) {
this . list = list ;
}
public int getStartIndex ( ) {
return startIndex ;
}
public void setStartIndex ( int startIndex ) {
this . startIndex = startIndex ;
}
}
Mapper 介面至少需要兩種方法，一種方法查詢總記錄數，另一種方法查詢資料。Worker 是我的資料庫的 pojo 類。
int getTotalRecord ( ) ;
List < Worker > selectAll ( @Param ( value = "startIndex" ) int startIndex , @Param ( value = "pageSize" ) int pageSize ) ;
以下程式碼是Worker對應的resultMap和對應介面方法的實現
< mapper namespace = " com.pagehelper.mapper.WorkerMapper " >
< resultMap id = " BaseResultMap " type = " com.pagehelper.pojo.Worker " >
< id column = " wid " property = " wid " jdbcType = " INTEGER " />
< result column = " password " property = " password" jdbcType = " VARCHAR " />
< result column = " company " property = " company " jdbcType = " VARCHAR " />
< result column = " department " property = " department " jdbcType = " VARCHAR " />
< result column = " job " property =" job " jdbcType = " VARCHAR " />
< result column = " name " property = " name " jdbcType = " VARCHAR " />
< result column = " sex " property = " sex " jdbcType = " VARCHAR " />
< result column = "age " property = " age " jdbcType = " INTEGER " />
< result column = " tel " property = " tel " jdbcType = " VARCHAR " />
< result column = " email " property = " email " jdbcType = " VARCHAR " />
< result column = "regist_time " Property = " registTime " the jdbcType = " TIMESTAMP " />
< Result column = " IMG " Property = " IMG " the jdbcType = " VARCHAR " />
</ The resultMap >
< SELECT ID = " getTotalRecord " the resultType = " int " >
SELECT COUNT(wid) FROM worker
</ select >
< select id = " selectAll " resultMap = " BaseResultMap " >
SELECT wid, password, company, department,job, name, sex, age, tel, email, regist_time,img FROM worker limit #{startIndex},#{pageSize}
</ select >
</ mapper >
服務層呼叫程式碼：
@Override
public PageBean < the Worker > the getAll ( int pageNow ) {
/* Get the total number of calls to method of recording getTotalRecord () */
int totalRecord = workerMapper . GetTotalRecord ( ) ;
/* instantiate a class PageBean tool parameters passed pageNow, totalRecord, the PageSize fixed constructor I used here */
PageBean < Worker > pageBean = new PageBean < > ( pageNow , totalRecord ) ;
/* Call data query method selectAll (StartIndex, PageSize), parameters PageBean properties, the results of the query package to PageBean of the List */
pageBean . SetList ( workerMapper . A selectAll ( pageBean . GetStartIndex ( ) , pageBean . GetPageSize ( ) ) ) ;
/*Return PageBean object*/
return pageBean ;
}
因為構建的java專案沒有寫Controller和page，所以使用test方法顯示查詢結果
package com . pagehelper . test ;
import com . pagehelper . mapper . WorkerMapper ;
import com . pagehelper . pojo . Worker ;
import com . pagehelper . service . impl . WorkerServiceImpl ;
import com . pagehelper . util . PageBean ;
import org . apache . ibatis . io . Resources ;
importorg . apache . ibatis . session . SqlSession ;
import org . apache . ibatis . session . SqlSessionFactory ;
import org . apache . ibatis . session . SqlSessionFactoryBuilder ;
import java . io . IOException ;
import java . io . InputStream ;
public class Test1 {
public static void main ( String [ ] args ) throws IOException {
/*Get and load configuration file*/
String resource = "mybatis-config.xml" ;
InputStream inputStream = Resources . getResourceAsStream ( resource ) ;
/*Create a SqlSessionFactory session factory*/
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder ( ) . Build ( inputStream ) ;
/*Production SQLSession*/
The SqlSession the session = the sessionFactory . The openSession ( ) ;
/* realized obtained WorkerMapper interface */
WorkerMapper Mapper = the session . GetMapper ( WorkerMapper . Class ) ;
/* the Controller layer calls Service layer methods, examples of WorkerService */
WorkerServiceImpl workerService = new new WorkerServiceImpl ( mapper ) ;
/*Call WorkerService method, return PageBean, encapsulate paging related data
* Controller or after get data request is transmitted to the front end module to PageBean page, the page can obtain data directly via EL database, the current page number, total number of pages, and other related parameters */
PageBean < the Worker > pageBean = workerService . The getAll ( . 1 ) ;
/* print the total number of records TotalRecord */
the System . OUT . the println ( "total number of records:" + pageBean . getTotalRecord ( ) ) ( ) ) ; /* print from the database acquired data */for ( the worker worker : pageBean . getList ( ) ;
/* * print pages TotalPage/
the System . OUT . the println ( "pages: " + pageBean . getTotalPage
) {
System . OUT . The println ( worker ) ;
}
}
}
操作結果
log4j:ERROR Could not find value for key log4j.appender.LogFIle
log4j:ERROR Could not instantiate appender named "LogFIle".
2019-07-24 09:26:41 [main:1]-[DEBUG] ==> Preparing: SELECT COUNT(wid) FROM worker
2019-07-24 09:26:41 [main:56]-[DEBUG] ==> Parameters:
2019-07-24 09:26:41 [main:123]-[DEBUG] <== Total: 1
2019-07-24 09:26:41 [main:131]-[DEBUG] ==> Preparing: SELECT wid, password, company, department,job, name, sex, age, tel, email, regist_time,img FROM worker limit ?,?
2019-07-24 09:26:41 [main:132]-[DEBUG] ==> Parameters: 0(Integer), 5(Integer)
2019-07-24 09:26:41 [main:148]-[DEBUG] <== Total: 5
Total records: 29
Total pages: 6
Worker{wid=100001, password='admin', company='Soft Emperor', department='Development Department', job='Super Admin', name='Super Admin', sex='Male', age= 18, tel='123', email='[email protected]', registTime=Sat Jul 20 11:33:18 CST 2019, img='default.jpg'}
Worker{wid=100002, password='123', company='Soft Emperor Group', department='Development Department', job='Employee', name='Administrator', sex='Male', age=122, tel='123', email='[email protected]', registTime=Sat Jul 20 16:00:59 CST 2019, img='default.jpg'}
Worker{wid=100003, password='admin', company='Soft Emperor', department='Development Department', job='Administrator', name='Administrator', sex='Male', age=18, tel='123', email='[email protected]', registTime=Sat Jul 20 11:33:20 CST 2019, img='default.jpg'}
Worker{wid=100004, password='123', company='Soft Emperor', department='Development Department', job='BOSS', name='123', sex='男', age=18, tel= '123', email='123', registTime=Sat Jul 20 15:10:33 CST 2019, img='default.jpg'}
Worker{wid=100005, password='123', company='Soft Emperor Group', department='Personnel Department', job='Manager', name='Sada', sex='Male', age=18, tel='123', email='123', registTime=Sat Jul 20 15:10:50 CST 2019, img='default.jpg'}
Process finished with exit code 0
Java開發工具還有很多，大家可要多多瞭解，在以後的學習中還會用到。