MybatisPlus分页插件PaginationInterceptor实战

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配置分页插件

@Configuration
public class MybatisConfig {
  
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        return new PaginationInterceptor();
    }
}

高版本SpringBoot中，会提示这种写法已过时, 所以采用另一种写法MybatisPlusInterceptor：

@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor() {
    MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
    interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.H2));
    return interceptor;
}

MybatisPlusInterceptor

该插件是核心插件，目前代理了如下方法：

• Executor#query
• Executor#update
• StatementHandler#prepare

属性

private List<InnerInterceptor> interceptors = new ArrayList<>();

InnerInterceptor，我们提供的插件都将基于此接口来实现功能 目前已有的功能：

• 自动分页: PaginationInnerInterceptor
• 多租户:TenantLineInnerInterceptor
• 动态表名: DynamicTableNameInnerInterceptor
• 乐观锁：OptimisticLockerInnerInterceptor
• sql性能规范: IllegalSQLInnerInterceptor
• 防止全表更新与删除: BlockAttackInnerInterceptor

使用多个功能需要注意顺序关系，建议使用如下顺序

• 多租户
• 动态表名
• 分页
• 乐观锁
• sql性能规范
• 防止全表更新与删除

对sql进行单次改造的优先放入，不对sql进行改造的最后放入

Mapper及mapper.xml

@Mapper
public interface UserMapper extends BaseMapper<User> {
    List<User> findPageUsers(Page<User> page);
}

<select id="findPageUsers" resultType="org.wxmx.mybatis_plus_study.entity.User">
    select *
    from `user`
</select>

测试类

简单的分页查询

@SpringBootTest
class MybatisPlusStudyApplicationTests {
  
    @Resource
    UserMapper userMapper;
    @Test
    void contextLoads() {
        Page<User> page = new Page<>(1, 3);
        List<User> pageUsers = userMapper.findPageUsers(page);
        page.setRecords(pageUsers);
        System.out.println(page);
    }
}

运行结果:

JsqlParserCountOptimize sql=select *
        from `user`
==>  Preparing: SELECT COUNT(1) FROM `user`
==> Parameters: 
<==    Columns: COUNT(1)
<==        Row: 9
==>  Preparing: select * from `user` LIMIT ?
==> Parameters: 3(Long)
<==    Columns: id, name, age
<==        Row: 39a773890a1b12b8a072c1be02ff3cdc, aaa, 12
<==        Row: 3b25fb904548c28b7ac6882d86c7ae5f, wdh, 12
<==        Row: 8b0397fcdfebe37d1d26175c17ed3725, wdh, 12
<==      Total: 3

带查询条件的分页查询

此方法是使用PaginationInterceptor 作为分页插件.

@Test
void contextLoads() {
    Page<User> page = new Page<>(1, 2);
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.eq("name", "wdh");
    Page<User> page1 = userMapper.selectPage(page, queryWrapper);
   	page.setRecords(page1.getRecords()).getRecords().forEach(System.out::println);
}

运行结果:

JsqlParserCountOptimize sql=SELECT  id,name,age  FROM user 

 WHERE (name = ?)
==>  Preparing: SELECT COUNT(1) FROM user WHERE (name = ?)
==> Parameters: wdh(String)
<==    Columns: COUNT(1)
<==        Row: 5
==>  Preparing: SELECT id,name,age FROM user WHERE (name = ?) LIMIT ?
==> Parameters: wdh(String), 2(Long)
<==    Columns: id, name, age
<==        Row: 3b25fb904548c28b7ac6882d86c7ae5f, wdh, 12
<==        Row: 8b0397fcdfebe37d1d26175c17ed3725, wdh, 12
<==      Total: 2
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6a0f2853]
User(id=3b25fb904548c28b7ac6882d86c7ae5f, name=wdh, age=12)
User(id=8b0397fcdfebe37d1d26175c17ed3725, name=wdh, age=12)

Page

简单分页模型, 有如下几个主要属性

/**
 * 查询数据列表
 */
protected List<T> records = Collections.emptyList();

/**
 * 总数
 */
protected long total = 0;

/**
 * 每页显示条数，默认 10
 */
protected long size = 10;

/**
 * 当前页
 */
protected long current = 1;

注意事项

在编写mapper.xml中的SQL语句的时候, 语句末尾不能使用 ; 结尾，因为做分页时，会在编写的SQL语句后面拼接Limit语句，导致出现SQL语法错误(SQLSyntaxErrorException)。如下：

JsqlParserCountOptimize sql=select *
        from `user`;
==>  Preparing: SELECT COUNT(1) FROM `user`
==> Parameters: 
<==    Columns: COUNT(1)
<==        Row: 9
==>  Preparing: select * from `user`; LIMIT ?
==> Parameters: 3(Long)
org.springframework.jdbc.BadSqlGrammarException: 

### Error querying database.  Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'LIMIT 3' at line 1

### The error may exist in org/wxmx/mybatis_plus_study/mapper/UserMapper.xml

### The error may involve defaultParameterMap

### The error occurred while setting parameters

### SQL: select *         from `user`; LIMIT ?

### Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'LIMIT 3' at line 1

; bad SQL grammar []; nested exception is java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'LIMIT 3' at line 1