Shulou(Shulou.com)06/01 Report--

In this article Xiaobian for you to introduce in detail "how to achieve paging function in Java", the content is detailed, the steps are clear, the details are handled properly, I hope this "how to achieve paging function in Java" article can help you solve your doubts, the following follows the editor's ideas slowly in depth, together to learn new knowledge.

I. limit keyword

By using this method, let's take a look at the code of the relevant service layer:

Service@Transactionalpublic class ImplStudentService implements StudentService {@ Resourceprivate StudentDao studentDao; @ Override public List selectAllStudent (String province, Integer offset, Integer limit) {return studentDao.selectAll (province,offset,limit);}}

The code for the corresponding sql statement is as follows:

Select * from student where province = # {province} limit # {offset}, # {limit}

II. Hibernate pagination

First, let's take a look at the code of the service layer:

@ Override public List getStudents (Integer pageNo,Integer pageSize) throws Exception {/ / paged data int [] startIdAndCount = new int [2]; startIdAndCount [0] = pageNo * pageSize; startIdAndCount [1] = pageSize; return studentDao.selectStudentsByPage (startIdAndCount);}

Unlike the limit keyword method, the dao layer is used in the hibernate method, and the code is as follows:

@ Override public List getStudents (Integer pageNo,Integer pageSize) throws Exception {/ / paged data int [] startIdAndCount = new int [2]; startIdAndCount [0] = pageNo * pageSize; startIdAndCount [1] = pageSize; return studentDao.selectStudentsByPage (startIdAndCount);}

3. Intercept the paging of List query results

For this method, it seems relatively simple. Let's look directly at the code:

@ Override public List getStudents (Integer pageNo,Integer pageSize) throws Exception {/ / paged data int [] startIdAndCount = new int [2]; startIdAndCount [0] = pageNo * pageSize; startIdAndCount [1] = pageSize; return studentDao.selectStudentsByPage (startIdAndCount);}

Fourth, mybatis framework pageHelper plug-in paging

First, let's take a look at the Spring integration section:

The import pom.xml code is as follows:

@ Override public List getStudents (Integer pageNo,Integer pageSize) throws Exception {/ / paged data int [] startIdAndCount = new int [2]; startIdAndCount [0] = pageNo * pageSize; startIdAndCount [1] = pageSize; return studentDao.selectStudentsByPage (startIdAndCount);}

The configuration file code for our configuration project is as follows:

Classpath*:com/yyz/mapper/*Mapper.xml helperDialect=mysql Reasonable=true params=count=countSql supportMethodsArguments=true autoRuntimeDialect=true

SpringBoot consolidation:

@ Override public List getStudents (Integer pageNo,Integer pageSize) throws Exception {/ / paged data int [] startIdAndCount = new int [2]; startIdAndCount [0] = pageNo * pageSize; startIdAndCount [1] = pageSize; return studentDao.selectStudentsByPage (startIdAndCount);}

Configure the project application.xml file with the code as follows:

@ Override public List getStudents (Integer pageNo,Integer pageSize) throws Exception {/ / paged data int [] startIdAndCount = new int [2]; startIdAndCount [0] = pageNo * pageSize; startIdAndCount [1] = pageSize; return studentDao.selectStudentsByPage (startIdAndCount);}

The following parameters are also provided for us in the paging plug-in:

Dialect: PageHelper is used for paging by default. If you want to implement your own paging logic, you can do so.

The Dialect (com.github.pagehelper.Dialect) interface, and then configure the property to be the fully qualified name of the implementation class. The following parameters have no effect when using a custom dialect implementation.

HelperDialect: the paging plug-in automatically detects the current database link and automatically selects the appropriate paging method oracle,mysql,mariadb,sqlite,hsqldb,postgresql,db2,sqlserver,informix,h3,sqlserver2012,derby. Special note: when using a SqlServer2012 database, you need to specify it as sqlserver2012 manually, otherwise you will use SqlServer2005 for paging. OffsetAsPageNum: the default value is false, which is valid when using RowBounds as the paging parameter. When this parameter is set to true, the offset parameter in RowBounds is used as pageNum, and page number and page size can be used for paging.

RowBoundsWithCount: the default value is false, which is valid when using RowBounds as the paging parameter. When this parameter is set to true, using RowBounds paging makes an count query.

PageSizeZero: the default value is false, and when this parameter is set to true, all results will be queried if pageSize=0 or RowBounds.limit = 0 (equivalent to no paging query is executed, but the returned result is still of type Page).

Reasonable: paging rationalization parameter. Default is false. When this parameter is set to true, pageNumpages (when the total is exceeded), the last page is queried. When you default to false, the query is directly based on the parameters.

Params: in order to support the startPage (Object params) method, this parameter is added to configure the parameter mapping, which is used to take values from the object according to the property name. PageNum,pageSize,count,pageSizeZero,reasonable can be configured, and the default value of the mapping is not configured. The default value is pageNum=pageNum;pageSize=pageSize;count=countSql;reasonable=reasonable;pageSizeZero=pageSizeZero.

SupportMethodsArguments: paging parameters can be passed through Mapper API parameters. The default value is false. The paging plug-in automatically selects values from the parameter values of the query method according to the fields configured by params above, and automatically paging when the appropriate values are found.

AggregateFunctions: default to aggregate functions of all common databases. Aggregate functions are allowed to be added manually (affecting the number of rows). All functions that begin with aggregate functions will be covered by one layer during count conversion. Other functions and columns are replaced with count (0), where the count column can be configured on its own.

Of course, among these method parameters, when offsetAsPageNum=false, due to problems with PageNum in the code, RowBound will force reasonable to be false when querying, but the use of the PageHelper.startPage method will not be affected. Let's take a look at the code of the service layer of related content:

Overridepublic ResponseResult selectAllStudent (Integer pageNum, Integer pageSize) {Map map = new HashMap (); PageHelper.startPage (pageNum,pageSize); List students = studentMapper.selectAllStudents (); PageInfo pageInfo = new PageInfo (students); long total = pageInfo.getTotal (); map.put ("result", pageInfo); map.put ("count", total); return ResponseResultUtil.success (map)

5. SpringData pagination

The code at the service layer is as follows:

Sort.Order travelDate = new Sort.Order (Sort.Direction.DESC, "travelDate"); Sort.Order createdTime = new Sort.Order (Sort.Direction.DESC, "createdTime"); Sort sort = new Sort (travelDate, createdTime); Pageable pageable = new PageRequest (page, pageSize, sort); List items = null;try {items = travelRepository.getTravelItemsByTravelDateBetweenAndUserId (theStartDate, theEndDate, openId, pageable);} catch (Exception e) {throw new DatabaseRelatedException ("TravelRepository exception");}

This is the code about the service layer, so for the dao layer, the interface inherits the PagingAndSortingRepository interface, so we should note that we need to add the @ Repository annotation.

After reading this, the article "how to achieve paging in Java" has been introduced. If you want to master the knowledge of this article, you still need to practice and use it yourself. If you want to know more about related articles, you are welcome to follow the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.