Java使用MyBatis框架分頁(yè)的5種方式

更新時(shí)間：2020年04月22日 16:29:35 作者：~來了小老弟

這篇文章主要為大家詳細(xì)介紹了Java使用MyBatis框架分頁(yè)的5種方式，文中示例代碼介紹的非常詳細(xì)，具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下

本文為大家分享了Java使用MyBatis框架分頁(yè)的五種方式，供大家參考，具體內(nèi)容如下

初始準(zhǔn)備

1.創(chuàng)建分頁(yè)對(duì)象類，方便模塊間傳值

//PageInfo.java
import lombok.Data;

@Data
public class PageInfo {

 private int pageNo;

 private int pageSize;

}

2.定義DAO層接口

import org.apache.ibatis.session.RowBounds;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface UserMapper {

 User selectByUser(User user);
 List<User> selectAll();
 List<User> selectByPageInfo(PageInfo info);
 List<User> selectByInterceptor(PageInfo info);

 List<User> selectByRowBounds(RowBounds rowBounds);

}

3.mapper中定義結(jié)果集合BaseResult

<resultMap id="BaseResult" type="cn.edu.yau.pojo.User">
 <id property="id" column="id" jdbcType="INTEGER"></id>
 <result property="username" column="username" jdbcType="VARCHAR"></result>
 <result property="password" column="password" jdbcType="VARCHAR"></result>
 </resultMap>

一、原始切分：最原始方法，不建議使用

1.mapper代碼:查詢所有數(shù)據(jù)

<select id="selectAll" resultMap="BaseResult">
 select * from tb_user
</select>

2.業(yè)務(wù)層代碼:利用List的subList()方法對(duì)數(shù)據(jù)進(jìn)行切片

public List<User> findByAll(PageInfo info) {
 List<User> users = userMapper.selectAll();
 return users.subList(info.getPageNo(), info.getPageSize());
 }

3.控制層代碼

@RequestMapping(value = "/userlist_1", method = RequestMethod.GET)
@ResponseBody
 public Result findUserBySubList(PageInfo info) {
 List<User> users = userService.findByAll(info);
 if(users.size() == 0) {
  return ResultGenerator.genFailResult("未查找到用戶");
 }
 return ResultGenerator.genSuccessResult(users);
 }

二、LIMIT關(guān)鍵字

1.mapper代碼:利用limit關(guān)鍵字實(shí)現(xiàn)分頁(yè)

<select id="selectByPageInfo" resultMap="BaseResult">
 select * from tb_user limit #{pageNo}, #{pageSize}
</select>

2.業(yè)務(wù)層直接調(diào)用

public List<User> findByPageInfo(PageInfo info) {
 return userMapper.selectByPageInfo(info);
 }

3.控制層直接調(diào)用

三、RowBounds實(shí)現(xiàn)分頁(yè)

1.在DAO層定義好所要傳輸?shù)姆猪?yè)信息，類型為RowBounds

2.mapper層：查詢所有數(shù)據(jù)

3.業(yè)務(wù)層：將PageInfo信息封裝成RowBounds,調(diào)用DAO層方法

public List<User> findByRowBounds(PageInfo info) {
 return userMapper.selectByRowBounds(new RowBounds(info.getPageNo(), info.getPageSize()));
 }

4.控制層直接調(diào)用

四、MyBatis的Interceptor實(shí)現(xiàn):實(shí)現(xiàn)復(fù)雜，需要明白MyBatis的實(shí)現(xiàn)

1.創(chuàng)建Interceptor

import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;

import java.sql.Connection;
import java.util.Properties;

/**
 * 利用MyBatis攔截器進(jìn)行分頁(yè)
 *
 * @Intercepts 說明是一個(gè)攔截器
 * @Signature 攔截器的簽名
 * type 攔截的類型 四大對(duì)象之一( Executor,ResultSetHandler,ParameterHandler,StatementHandler)
 * method 攔截的方法
 * args 參數(shù),高版本需要加個(gè)Integer.class參數(shù),不然會(huì)報(bào)錯(cuò)
 *
 */
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class DefinedPageInterceptor implements Interceptor {

 @Override
 public Object intercept(Invocation invocation) throws Throwable {
 //獲取StatementHandler,默認(rèn)的是RoutingStatementHandler
 StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
 //獲取StatementHandler的包裝類
 MetaObject metaObject = SystemMetaObject.forObject(statementHandler);
 //分隔代理對(duì)象
 while (metaObject.hasGetter("h")) {
  Object obj = metaObject.getValue("h");
  metaObject = SystemMetaObject.forObject(obj);
 }
 while (metaObject.hasGetter("target")) {
  Object obj = metaObject.getValue("target");
  metaObject = SystemMetaObject.forObject(obj);
 }
 //獲取查看接口映射的相關(guān)信息
 MappedStatement mappedStatement = (MappedStatement) metaObject.getValue("delegate.mappedStatement");
 String mapId = mappedStatement.getId();
 //攔截以ByInterceptor結(jié)尾的請(qǐng)求，統(tǒng)一實(shí)現(xiàn)分頁(yè)
 if (mapId.matches(".+ByInterceptor$")) {
  System.out.println("LOG:已觸發(fā)分頁(yè)攔截器");
  //獲取進(jìn)行數(shù)據(jù)庫(kù)操作時(shí)管理參數(shù)的Handler
  ParameterHandler parameterHandler = (ParameterHandler) metaObject.getValue("delegate.parameterHandler");
  //獲取請(qǐng)求時(shí)的參數(shù)
  PageInfo info = (PageInfo) parameterHandler.getParameterObject();
  //獲取原始SQL語(yǔ)句
  String originalSql = (String) metaObject.getValue("delegate.boundSql.sql");
  //構(gòu)建分頁(yè)功能的SQL語(yǔ)句
  String sql = originalSql.trim() + " limit " + info.getPageNo() + ", " + info.getPageSize();
  metaObject.setValue("delegate.boundSql.sql", sql);
 }
 //調(diào)用原對(duì)象方法，進(jìn)入責(zé)任鏈下一級(jí)
 return invocation.proceed();
 }

 @Override
 public Object plugin(Object target) {
 //生成Object對(duì)象的動(dòng)態(tài)代理對(duì)象
 return Plugin.wrap(target, this);
 }

 @Override
 public void setProperties(Properties properties) {
 //如果分頁(yè)每頁(yè)數(shù)量是統(tǒng)一的，可以在這里進(jìn)行統(tǒng)一配置，也就無需再傳入PageInfo信息了
 }
}

2.將Interceptor添加至MyBatisConfig中，這里采用JavaConfig的方式

@Bean
 public SqlSessionFactoryBean sqlSession() {
 SqlSessionFactoryBean sqlSession = new SqlSessionFactoryBean();
 sqlSession.setDataSource(dataSource());
 try {
  Resource[] resources = new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*.xml");
  sqlSession.setMapperLocations(resources);
  //配置自定義的Interceptro作為MyBatis的Interceptor,完成分頁(yè)操作
  DefinedPageInterceptor definedPageInterceptor = new DefinedPageInterceptor();
  sqlSession.setPlugins(new Interceptor[]{definedPageInterceptor});
  return sqlSession;
 } catch (IOException e) {
  e.printStackTrace();
 }
 return null;
 }

3.DAO層接口方法名需要和代碼中自定義的".+ByInterceptor$"正則表達(dá)式相匹配,mapper的書寫依然是查詢所有數(shù)據(jù)

<select id="selectByInterceptor" resultMap="BaseResult">
 select * from tb_user
</select>

4.業(yè)務(wù)層直接調(diào)用

5.控制層直接調(diào)用

五、開源項(xiàng)目PageHelper實(shí)現(xiàn)：本質(zhì)還是自己封裝了個(gè)Interceptor

1.引入PageHelper的jar包

<dependency>
 <groupId>com.github.pagehelper</groupId>
 <artifactId>pagehelper</artifactId>
 <version>5.1.10</version>
</dependency>

2.配置PageInterceptor

public PageInterceptor initPageInterceptor(){
 PageInterceptor pageInterceptor = new PageInterceptor();
 Properties properties = new Properties();
 //設(shè)置數(shù)據(jù)庫(kù)類型
 properties.setProperty("helperDialect", "mysql");
 //該參數(shù)默認(rèn)為false
 //設(shè)置為true時(shí)，會(huì)將RowBounds第一個(gè)參數(shù)offset當(dāng)成pageNum頁(yè)碼使用
 //和startPage中的pageNum效果一樣
 properties.setProperty("offsetAsPageNum", "true");
 //該參數(shù)默認(rèn)為false
 //設(shè)置為true時(shí)，使用RowBounds分頁(yè)會(huì)進(jìn)行count查詢
 properties.setProperty("rowBoundsWithCount", "true");
 pageInterceptor.setProperties(properties);
 return pageInterceptor;
 }

 @Bean
 public SqlSessionFactoryBean sqlSession() {
 SqlSessionFactoryBean sqlSession = new SqlSessionFactoryBean();
 sqlSession.setDataSource(dataSource());
 try {
  Resource[] resources = new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*.xml");
  sqlSession.setMapperLocations(resources);
  //配置PageHelper作為MyBatis的Interceptor，完成分頁(yè)操作
  PageInterceptor pageInterceptor = this.initPageInterceptor();
  //配置自定義的Interceptro作為MyBatis的Interceptor,完成分頁(yè)操作
  DefinedPageInterceptor definedPageInterceptor = new DefinedPageInterceptor();
  sqlSession.setPlugins(new Interceptor[]{pageInterceptor, definedPageInterceptor});
  return sqlSession;
 } catch (IOException e) {
  e.printStackTrace();
 }
 return null;
 }

3.mapper依然是查詢所有數(shù)據(jù)

4.為DAO層再封裝一次方法

@Repository
public class PageHelperHandler {

 @Autowired
 private SqlSessionFactory sqlSessionFactory;

 public List<User> findByPageHelper(PageInfo info) {
 SqlSession session = sqlSessionFactory.openSession();
 PageHelper.startPage(info.getPageNo(), info.getPageSize());
 //寫到要使用到的類名和方法名
 List<User> users = session.selectList("cn.edu.yau.mapper.UserMapper.selectAll");
 return users;
 }

}

6.業(yè)務(wù)層直接調(diào)用Handler

7.控制層直接調(diào)用

以上就是本文的全部?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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