PaginationInnerInterceptor
此插件是核心插件,目前代理了 Executor#query 和 Executor#update 和 StatementHandler#prepare 方法。
在SpringBoot环境中配置方式如下：
/**
* @author giserDev
* @description 配置分页插件、方言、mapper包扫描等
* @date 2023-12-13 23:23:35
*/
@Configuration
@MapperScan("com.giser.mybatisplus.mapper")
public class MyBatisPlusConfig {
@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor(){
MybatisPlusInterceptor mybatisPlusInterceptor = new MybatisPlusInterceptor();
mybatisPlusInterceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
return mybatisPlusInterceptor;
}
}
测试分页功能：
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.giser.mybatisplus.mapper.UserMapper;
import com.giser.mybatisplus.pojo.User;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
/**
* @author giserDev
* @description
* @date 2023-12-13 23:28:43
*/
@Slf4j
@SpringBootTest
public class MyBatisPlusPluginsTest {
@Autowired
private UserMapper userMapper;
@Test
public void testMyBatisPlusPage(){
Page<User> page = new Page<>(1,3);
userMapper.selectPage(page, null);
log.info("分页查询结果为：{}", page);
}
}
如何自定义分页？
# mybatis-plus配置
mybatis-plus:
configuration:
# 引入日志
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
global-config:
db-config:
# 配置MybatisPlus操作的表的前缀
table-prefix: t_
# 配置MybatisPlus的主键生成策略
id-type: assign_id
# 指定类型别名
type-aliases-package: com.giser.mybatisplus.pojo
在Mapper接口中定义分页方法：
@Repository
public interface UserMapper extends BaseMapper<User> {
/**
* 利用MybatisPlus的分页功能
* @param page 分页对象，必须在第一个参数位置，传递参数 Page 即自动分页
* @param userName 查询条件
* @return 结果
*/
Page<User> selectPageByName(@Param("page") Page<User> page, @Param("userName") String userName);
}
在Mapper.xml文件中实现分页语句：
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.giser.mybatisplus.mapper.UserMapper">
<select id="selectPageByName" resultType="User">
select * from user where user_name = #{userName}
</select>
</mapper>
分页测试：
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.giser.mybatisplus.mapper.UserMapper;
import com.giser.mybatisplus.pojo.User;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
@Slf4j
@SpringBootTest
public class MyBatisPlusPluginsTest {
@Autowired
private UserMapper userMapper;
/**
* ==> Preparing: SELECT COUNT(*) AS total FROM user WHERE is_deleted = 0
* ==> Parameters:
* <== Columns: total
* <== Row: 25
* <== Total: 1
* ==> Preparing: SELECT id,user_name AS name,age,email,is_deleted FROM user WHERE is_deleted=0 LIMIT ?
* ==> Parameters: 3(Long)
* <== Columns: id, name, age, email, is_deleted
* <== Row: 1, Jone, 18, test1@baomidou.com, 0
* <== Row: 2, 窃听风云, 23, giserDev@163.com, 0
* <== Row: 3, Tom, 28, test3@baomidou.com, 0
* <== Total: 3
* Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3a109ff7]
* 分页查询结果为：com.baomidou.mybatisplus.extension.plugins.pagination.Page@5ee77baf
* 分页查询记录结果为：[User(id=1, name=Jone, age=18, email=test1@baomidou.com, isDeleted=0), User(id=2, name=窃听风云, age=23, email=giserDev@163.com, isDeleted=0), User(id=3, name=Tom, age=28, email=test3@baomidou.com, isDeleted=0)]
* 分页查询记录条数为：25
* 分页查询当前页码为：1
* 分页查询每页大小为：3
*/
@Test
public void testMyBatisPlusPage(){
Page<User> page = new Page<>(1,3);
userMapper.selectPage(page, null);
log.info("分页查询结果为：{}", page);
log.info("分页查询记录结果为：{}", page.getRecords());
log.info("分页查询记录条数为：{}", page.getTotal());
log.info("分页查询当前页码为：{}", page.getCurrent());
log.info("分页查询每页大小为：{}", page.getSize());
}
/**
* ==> Preparing: SELECT COUNT(*) AS total FROM user WHERE user_name = ?
* ==> Parameters: 李雷(String)
* <== Columns: total
* <== Row: 1
* <== Total: 1
* ==> Preparing: select * from user where user_name = ? LIMIT ?
* ==> Parameters: 李雷(String), 3(Long)
* <== Columns: id, user_name, age, email, is_deleted
* <== Row: 1734579107187970050, 李雷, 12, null, 1
* <== Total: 1
* Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@a316f6b]
* 分页查询结果为：com.baomidou.mybatisplus.extension.plugins.pagination.Page@48368a08
* 分页查询记录结果为：[User(id=1734579107187970050, name=null, age=12, email=null, isDeleted=1)]
* 分页查询记录条数为：1
* 分页查询当前页码为：1
* 分页查询每页大小为：3
*/
@Test
void testAutoPage(){
Page<User> page = new Page<>(1,3);
userMapper.selectPageByName(page, "李雷");
log.info("分页查询结果为：{}", page);
log.info("分页查询记录结果为：{}", page.getRecords());
log.info("分页查询记录条数为：{}", page.getTotal());
log.info("分页查询当前页码为：{}", page.getCurrent());
log.info("分页查询每页大小为：{}", page.getSize());
}
}
问题：分页参数处理原理
拦截执行的语句
org.apache.ibatis.plugin.Plugin#invoke
if (methods != null && methods.contains(method)) {
return interceptor.intercept(new Invocation(target, method, args));
}
com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor#intercept
@Override
public Object intercept(Invocation invocation) throws Throwable {
// ...
for (InnerInterceptor query : interceptors) {
// com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor#willDoQuery
// willDoQuery()，先判断总条数，决定是否执行sql语句
if (!query.willDoQuery(executor, ms, parameter, rowBounds, resultHandler, boundSql)) {
return Collections.emptyList();
}
// beforeQuery()，处理排序、分页方言
query.beforeQuery(executor, ms, parameter, rowBounds, resultHandler, boundSql);
}
// ...
@Override
public boolean willDoQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
// 查找分页参数
IPage<?> page = ParameterUtils.findPage(parameter).orElse(null);
if (page == null || page.getSize() < 0 || !page.searchCount()) {
return true;
}
// ...
// 组装统计语句，判断总条数
long total = 0;
if (CollectionUtils.isNotEmpty(result)) {
// 个别数据库 count 没数据不会返回 0
Object o = result.get(0);
if (o != null) {
total = Long.parseLong(o.toString());
}
}
page.setTotal(total);
// protected boolean continuePage(IPage<?> page)
// 返回是否继续执行后面的查询语句，执行则返回true,否则返回false
return continuePage(page);
}
willDoQuery()方法中包含查询分页参数的逻辑，如下：
/**
* 查找分页参数
*
* @param parameterObject 参数对象
* @return 分页参数
*/
public static Optional<IPage> findPage(Object parameterObject) {
if (parameterObject != null) {
// 若参数类型为Map，则从map中查找类型为IPage的参数，作为分页参数
if (parameterObject instanceof Map) {
Map<?, ?> parameterMap = (Map<?, ?>) parameterObject;
for (Map.Entry entry : parameterMap.entrySet()) {
if (entry.getValue() != null && entry.getValue() instanceof IPage) {
return Optional.of((IPage) entry.getValue());
}
}
} else if (parameterObject instanceof IPage) {
// 若参数类型为IPage，则直接返回，作为分页参数
return Optional.of((IPage) parameterObject);
}
}
return Optional.empty();
}
com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor#beforeQuery
@Override
public void beforeQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
IPage<?> page = ParameterUtils.findPage(parameter).orElse(null);
if (null == page) {
return;
}
// 处理 orderBy 拼接
boolean addOrdered = false;
String buildSql = boundSql.getSql();
List<OrderItem> orders = page.orders();
if (CollectionUtils.isNotEmpty(orders)) {
addOrdered = true;
buildSql = this.concatOrderBy(buildSql, orders);
}
// size 小于 0 且不限制返回值则不构造分页sql
Long _limit = page.maxLimit() != null ? page.maxLimit() : maxLimit;
if (page.getSize() < 0 && null == _limit) {
if (addOrdered) {
PluginUtils.mpBoundSql(boundSql).sql(buildSql);
}
return;
}
handlerLimit(page, _limit);
// 查找方言，在配置分页插件时，设置了DbType，此时可确定方言，如此时返回的是com.baomidou.mybatisplus.extension.plugins.pagination.dialects.MySqlDialect
IDialect dialect = findIDialect(executor);
final Configuration configuration = ms.getConfiguration();
// 构造分页语句！！！com.baomidou.mybatisplus.extension.plugins.pagination.dialects.IDialect#buildPaginationSql
// 此时dialect为MySqlDialect，会调用com.baomidou.mybatisplus.extension.plugins.pagination.dialects.MySqlDialect#buildPaginationSql来构造sql
DialectModel model = dialect.buildPaginationSql(buildSql, page.offset(), page.getSize());
// ...
// 此处绑定执行的sql语句model.getDialectSql()
mpBoundSql.sql(model.getDialectSql());
mpBoundSql.parameterMappings(mappings);
}
com.baomidou.mybatisplus.extension.plugins.pagination.dialects.MySqlDialect#buildPaginationSql
public class MySqlDialect implements IDialect {
@Override
public DialectModel buildPaginationSql(String originalSql, long offset, long limit) {
StringBuilder sql = new StringBuilder(originalSql).append(" LIMIT ").append(FIRST_MARK);
if (offset != 0L) {
sql.append(StringPool.COMMA).append(SECOND_MARK);
return new DialectModel(sql.toString(), offset, limit).setConsumerChain();
} else {
return new DialectModel(sql.toString(), limit).setConsumer(true);
}
}
}
