小编这次要给大家分享的是Java如何使用MyBatis框架分页，文章内容丰富，感兴趣的小伙伴可以来了解一下，希望大家阅读完这篇文章之后能够有所收获。
初始准备
1.创建分页对象类，方便模块间传值
//PageInfo.java
import lombok.Data;
@Data
public class PageInfo {
private int pageNo;
private int pageSize;
}2.定义DAO层接口
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中定义结果集合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，不建议使用
1.mapper代码:查询所有数据
<select id="selectAll" resultMap="BaseResult"> select * from tb_user </select>
2.业务层代码:利用List的subList()方法对数据进行切片
public List<User> findByAll(PageInfo info) {
List<User> users = userMapper.selectAll();
return users.subList(info.getPageNo(), info.getPageSize());
}3.控制层代码
@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("未查找到用户");
}
return ResultGenerator.genSuccessResult(users);
}二、LIMIT关键字
1.mapper代码:利用limit关键字实现分页
<select id="selectByPageInfo" resultMap="BaseResult">
select * from tb_user limit #{pageNo}, #{pageSize}
</select>2.业务层直接调用
public List<User> findByPageInfo(PageInfo info) {
return userMapper.selectByPageInfo(info);
}3.控制层直接调用
三、RowBounds实现分页
1.在DAO层定义好所要传输的分页信息，类型为RowBounds
2.mapper层：查询所有数据
3.业务层：将PageInfo信息封装成RowBounds,调用DAO层方法
public List<User> findByRowBounds(PageInfo info) {
return userMapper.selectByRowBounds(new RowBounds(info.getPageNo(), info.getPageSize()));
}4.控制层直接调用
四、MyBatis的Interceptor实现:实现复杂，需要明白MyBatis的实现
1.创建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拦截器进行分页
*
* @Intercepts 说明是一个拦截器
* @Signature 拦截器的签名
* type 拦截的类型 四大对象之一( Executor,ResultSetHandler,ParameterHandler,StatementHandler)
* method 拦截的方法
* args 参数,高版本需要加个Integer.class参数,不然会报错
*
*/
@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 {
//获取StatementHandler,默认的是RoutingStatementHandler
StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
//获取StatementHandler的包装类
MetaObject metaObject = SystemMetaObject.forObject(statementHandler);
//分隔代理对象
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);
}
//获取查看接口映射的相关信息
MappedStatement mappedStatement = (MappedStatement) metaObject.getValue("delegate.mappedStatement");
String mapId = mappedStatement.getId();
//拦截以ByInterceptor结尾的请求，统一实现分页
if (mapId.matches(".+ByInterceptor$")) {
System.out.println("LOG:已触发分页拦截器");
//获取进行数据库操作时管理参数的Handler
ParameterHandler parameterHandler = (ParameterHandler) metaObject.getValue("delegate.parameterHandler");
//获取请求时的参数
PageInfo info = (PageInfo) parameterHandler.getParameterObject();
//获取原始SQL语句
String originalSql = (String) metaObject.getValue("delegate.boundSql.sql");
//构建分页功能的SQL语句
String sql = originalSql.trim() + " limit " + info.getPageNo() + ", " + info.getPageSize();
metaObject.setValue("delegate.boundSql.sql", sql);
}
//调用原对象方法，进入责任链下一级
return invocation.proceed();
}
@Override
public Object plugin(Object target) {
//生成Object对象的动态代理对象
return Plugin.wrap(target, this);
}
@Override
public void setProperties(Properties properties) {
//如果分页每页数量是统一的，可以在这里进行统一配置，也就无需再传入PageInfo信息了
}
}2.将Interceptor添加至MyBatisConfig中，这里采用JavaConfig的方式
@Bean
public SqlSessionFactoryBean sqlSession() {
SqlSessionFactoryBean sqlSession = new SqlSessionFactoryBean();
sqlSession.setDataSource(dataSource());
try {
Resource[] resources = new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*.xml");
sqlSession.setMapperLocations(resources);
//配置自定义的Interceptro作为MyBatis的Interceptor,完成分页操作
DefinedPageInterceptor definedPageInterceptor = new DefinedPageInterceptor();
sqlSession.setPlugins(new Interceptor[]{definedPageInterceptor});
return sqlSession;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}3.DAO层接口方法名需要和代码中自定义的".+ByInterceptor$"正则表达式相匹配,mapper的书写依然是查询所有数据
<select id="selectByInterceptor" resultMap="BaseResult"> select * from tb_user </select>
4.业务层直接调用
5.控制层直接调用
五、开源项目PageHelper实现：本质还是自己封装了个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();
//设置数据库类型
properties.setProperty("helperDialect", "mysql");
//该参数默认为false
//设置为true时，会将RowBounds第一个参数offset当成pageNum页码使用
//和startPage中的pageNum效果一样
properties.setProperty("offsetAsPageNum", "true");
//该参数默认为false
//设置为true时，使用RowBounds分页会进行count查询
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作为MyBatis的Interceptor，完成分页操作
PageInterceptor pageInterceptor = this.initPageInterceptor();
//配置自定义的Interceptro作为MyBatis的Interceptor,完成分页操作
DefinedPageInterceptor definedPageInterceptor = new DefinedPageInterceptor();
sqlSession.setPlugins(new Interceptor[]{pageInterceptor, definedPageInterceptor});
return sqlSession;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}3.mapper依然是查询所有数据
4.为DAO层再封装一次方法
@Repository
public class PageHelperHandler {
@Autowired
private SqlSessionFactory sqlSessionFactory;
public List<User> findByPageHelper(PageInfo info) {
SqlSession session = sqlSessionFactory.openSession();
PageHelper.startPage(info.getPageNo(), info.getPageSize());
//写到要使用到的类名和方法名
List<User> users = session.selectList("cn.edu.yau.mapper.UserMapper.selectAll");
return users;
}
}6.业务层直接调用Handler
7.控制层直接调用
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