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這篇文章主要講解了“SpringBoot MP簡(jiǎn)單的分頁(yè)查詢測(cè)試怎么實(shí)現(xiàn)”,文中的講解內(nèi)容簡(jiǎn)單清晰,易于學(xué)習(xí)與理解,下面請(qǐng)大家跟著小編的思路慢慢深入,一起來(lái)研究和學(xué)習(xí)“SpringBoot MP簡(jiǎn)單的分頁(yè)查詢測(cè)試怎么實(shí)現(xiàn)”吧!
導(dǎo)入最新的mp依賴是第一步不然太低的版本什么都做不了,3,1以下的好像連分頁(yè)插件都沒(méi)有加進(jìn)去,所以我們用最新的3.5的,保證啥都有:
<dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.5.2</version> </dependency>
這里我們需要認(rèn)識(shí)兩個(gè)插件:mp的核心插件MybatisPlusInterceptor與自動(dòng)分頁(yè)插件PaginationInnerInterceptor。
MybatisPlusInterceptor的源碼(去掉中間的處理代碼):
public class MybatisPlusInterceptor implements Interceptor { private List<InnerInterceptor> interceptors = new ArrayList(); public MybatisPlusInterceptor() {} public Object intercept(Invocation invocation) throws Throwable {} public Object plugin(Object target) {} public void addInnerInterceptor(InnerInterceptor innerInterceptor) {} public List<InnerInterceptor> getInterceptors() {} public void setProperties(Properties properties) {} public void setInterceptors(final List<InnerInterceptor> interceptors) {} }
我們可以發(fā)現(xiàn)它有一個(gè)私有的屬性列表 List<InnerInterceptor> 而這個(gè)鏈表中的元素類型是InnerInterceptor。
InnerInterceptor源碼:
public interface InnerInterceptor { default boolean willDoQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException { return true; } default void beforeQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException { } default boolean willDoUpdate(Executor executor, MappedStatement ms, Object parameter) throws SQLException { return true; } default void beforeUpdate(Executor executor, MappedStatement ms, Object parameter) throws SQLException { } default void beforePrepare(StatementHandler sh, Connection connection, Integer transactionTimeout) { } default void beforeGetBoundSql(StatementHandler sh) { } default void setProperties(Properties properties) { } }
不難發(fā)現(xiàn)這個(gè)接口的內(nèi)容大致就是設(shè)置默認(rèn)的屬性,從代碼的意思上就是提供默認(rèn)的數(shù)據(jù)庫(kù)操作執(zhí)行時(shí)期前后執(zhí)行的一些邏輯,誰(shuí)實(shí)現(xiàn)它的方法會(huì)得到新的功能?
再看看PaginationInnerInterceptor插件的源碼:
public class PaginationInnerInterceptor implements InnerInterceptor { protected static final List<SelectItem> COUNT_SELECT_ITEM = Collections.singletonList((new SelectExpressionItem((new Column()).withColumnName("COUNT(*)"))).withAlias(new Alias("total"))); protected static final Map<String, MappedStatement> countMsCache = new ConcurrentHashMap(); protected final Log logger = LogFactory.getLog(this.getClass()); protected boolean overflow; protected Long maxLimit; private DbType dbType; private IDialect dialect; protected boolean optimizeJoin = true; public PaginationInnerInterceptor(DbType dbType) { this.dbType = dbType; } public PaginationInnerInterceptor(IDialect dialect) { this.dialect = dialect; } public boolean willDoQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException { IPage<?> page = (IPage)ParameterUtils.findPage(parameter).orElse((Object)null); if (page != null && page.getSize() >= 0L && page.searchCount()) { MappedStatement countMs = this.buildCountMappedStatement(ms, page.countId()); BoundSql countSql; if (countMs != null) { countSql = countMs.getBoundSql(parameter); } else { countMs = this.buildAutoCountMappedStatement(ms); String countSqlStr = this.autoCountSql(page, boundSql.getSql()); MPBoundSql mpBoundSql = PluginUtils.mpBoundSql(boundSql); countSql = new BoundSql(countMs.getConfiguration(), countSqlStr, mpBoundSql.parameterMappings(), parameter); PluginUtils.setAdditionalParameter(countSql, mpBoundSql.additionalParameters()); } CacheKey cacheKey = executor.createCacheKey(countMs, parameter, rowBounds, countSql); List<Object> result = executor.query(countMs, parameter, rowBounds, resultHandler, cacheKey, countSql); long total = 0L; if (CollectionUtils.isNotEmpty(result)) { Object o = result.get(0); if (o != null) { total = Long.parseLong(o.toString()); } } page.setTotal(total); return this.continuePage(page); } else { return true; } } public void beforeQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {...........省略之后全部的內(nèi)容........}
我們不難發(fā)現(xiàn)它實(shí)現(xiàn)了來(lái)自于InnerInterceptor的方法,這里面的源碼有時(shí)間需要好好處處邏輯。
我們知道了分頁(yè)插件和核心插件的關(guān)系,也就是我們可以將分頁(yè)插件添加入核心插件內(nèi)部的插件鏈表中去,從而實(shí)現(xiàn)多功能插件的使用。
配置mp插件,并將插件交由spring管理(我們用的是springboot進(jìn)行測(cè)試所以不需要使用xml文件):
import com.baomidou.mybatisplus.annotation.DbType; import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor; import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration public class MpConfig { /*分頁(yè)插件的配置*/ @Bean public MybatisPlusInterceptor mybatisPlusInterceptor() { /*創(chuàng)建mp攔截器*/ MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor(); /*創(chuàng)建分頁(yè)插件*/ PaginationInnerInterceptor pagInterceptor = new PaginationInnerInterceptor(); /*設(shè)置請(qǐng)求的頁(yè)面大于最大頁(yè)容量后的請(qǐng)求操作,true回調(diào)第一頁(yè),false繼續(xù)翻頁(yè),默認(rèn)翻頁(yè)*/ pagInterceptor.setOverflow(false); /*設(shè)置單頁(yè)分頁(yè)的條數(shù)限制*/ pagInterceptor.setMaxLimit(500L); /*設(shè)置數(shù)據(jù)庫(kù)類型*/ pagInterceptor.setDbType(DbType.MYSQL); /*將分頁(yè)攔截器添加到mp攔截器中*/ interceptor.addInnerInterceptor(pagInterceptor); return interceptor; } }
配置完之后寫一個(gè)Mapper接口:
import com.baomidou.mybatisplus.core.mapper.BaseMapper; import com.hlc.mp.entity.Product; import org.apache.ibatis.annotations.Mapper; @Mapper public interface ProductMapper extends BaseMapper<Product> { }
為接口創(chuàng)建一個(gè)服務(wù)類(一定按照mp編碼的風(fēng)格來(lái)):
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper; import com.baomidou.mybatisplus.extension.plugins.pagination.Page; import com.baomidou.mybatisplus.extension.service.IService; import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl; import com.hlc.mp.entity.Product; import com.hlc.mp.mapper.ProductMapper; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import java.util.List; @Service(value = "ProductService") public class ProductServiceImpl extends ServiceImpl<ProductMapper, Product> implements IService<Product> { @Autowired ProductMapper productMapper; /** * 根據(jù)傳入的頁(yè)碼進(jìn)行翻頁(yè) * * @param current 當(dāng)前頁(yè)碼(已經(jīng)約定每頁(yè)數(shù)據(jù)量是1條) * @return 分頁(yè)對(duì)象 */ public Page<Product> page(Long current) { /*current首頁(yè)位置,寫1就是第一頁(yè),沒(méi)有0頁(yè)之說(shuō),size每頁(yè)顯示的數(shù)據(jù)量*/ Page<Product> productPage = new Page<>(current, 1); /*條件查詢分頁(yè)*/ QueryWrapper<Product> queryWrapper = new QueryWrapper<>(); queryWrapper.eq("status", 0); productMapper.selectPage(productPage, queryWrapper); return productPage; } }
到這里我們可以看到分頁(yè)的具體方法就是,先創(chuàng)建一個(gè)分頁(yè)對(duì)象,規(guī)定頁(yè)碼和每一頁(yè)的數(shù)據(jù)量的大小,其次確定查詢操作的范圍,并使用BaseMapper<T>給予我們的查詢分頁(yè)方法selectPage(E page,Wapper<T> queryWapper)進(jìn)行查詢分頁(yè)的操作。
測(cè)試類:
@Test public void testPage(){ IPage<Product> productIPage = productService.page(2L); productIPage.getRecords().forEach(System.out::println); System.out.println("當(dāng)前頁(yè)碼"+productIPage.getCurrent()); System.out.println("每頁(yè)顯示數(shù)量"+productIPage.getSize()); System.out.println("總頁(yè)數(shù)"+productIPage.getPages()); System.out.println("數(shù)據(jù)總量"+productIPage.getTotal()); }
運(yùn)行查看分頁(yè)結(jié)果:
我們可以發(fā)現(xiàn)都正常的按照我們傳入的頁(yè)碼去查詢對(duì)應(yīng)的頁(yè)數(shù)據(jù)了,因?yàn)槲以O(shè)置的每頁(yè)只展示一條數(shù)據(jù),所以ID如果對(duì)應(yīng)頁(yè)碼就說(shuō)明分頁(yè)成功。
感謝各位的閱讀,以上就是“SpringBoot MP簡(jiǎn)單的分頁(yè)查詢測(cè)試怎么實(shí)現(xiàn)”的內(nèi)容了,經(jīng)過(guò)本文的學(xué)習(xí)后,相信大家對(duì)SpringBoot MP簡(jiǎn)單的分頁(yè)查詢測(cè)試怎么實(shí)現(xiàn)這一問(wèn)題有了更深刻的體會(huì),具體使用情況還需要大家實(shí)踐驗(yàn)證。這里是億速云,小編將為大家推送更多相關(guān)知識(shí)點(diǎn)的文章,歡迎關(guān)注!
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