前言

数据权限因分页问题，不可能通过代码对数据进行过滤处理，只能在数据库语句进行处理，而如果每个查询都进行特殊处理的话，是个巨大的工作量，在网上找到了mybatis的一种解决方案。

一、源码分析

1. 继承抽象类JsqlParserSupport并重写processSelect方法。JSqlParser是一个SQL语句解析器，它将SQL转换为Java类的可遍历层次结构。plus中也引入了JSqlParser包，processSelect可以对Select语句进行处理。
2. 实现InnerInterceptor接口并重写beforeQuery方法。InnerInterceptor是plus的插件接口，beforeQuery可以对查询语句执行前进行处理。
3. DataPermissionHandler作为数据权限处理器，是一个接口，提供getSqlSegment方法添加数据权限 SQL 片段。
4. 由上可知，我们只需要实现DataPermissionHandler接口，并按照业务规则处理SQL，就可以实现数据权限的功能。
5. DataPermissionInterceptor为mybatis-plus 3.4.2版本以上才有的功能。

package com.baomidou.mybatisplus.extension.plugins.inner;

import com.baomidou.mybatisplus.core.plugins.InterceptorIgnoreHelper;
import com.baomidou.mybatisplus.core.toolkit.PluginUtils;
import com.baomidou.mybatisplus.extension.parser.JsqlParserSupport;
import com.baomidou.mybatisplus.extension.plugins.handler.DataPermissionHandler;
import lombok.*;
import net.sf.jsqlparser.expression.Expression;
import net.sf.jsqlparser.statement.select.PlainSelect;
import net.sf.jsqlparser.statement.select.Select;
import net.sf.jsqlparser.statement.select.SelectBody;
import net.sf.jsqlparser.statement.select.SetOperationList;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;

import java.sql.SQLException;
import java.util.List;

/**
 * 数据权限处理器
 *
 * @author hubin
 * @since 3.4.1 +
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
@ToString(callSuper = true)
@EqualsAndHashCode(callSuper = true)
@SuppressWarnings({"rawtypes"})
public class DataPermissionInterceptor extends JsqlParserSupport implements InnerInterceptor {
    private DataPermissionHandler dataPermissionHandler;

    @Override
    public void beforeQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
        if (InterceptorIgnoreHelper.willIgnoreDataPermission(ms.getId())) return;
        PluginUtils.MPBoundSql mpBs = PluginUtils.mpBoundSql(boundSql);
        mpBs.sql(parserSingle(mpBs.sql(), ms.getId()));
    }

    @Override
    protected void processSelect(Select select, int index, String sql, Object obj) {
        SelectBody selectBody = select.getSelectBody();
        if (selectBody instanceof PlainSelect) {
            this.setWhere((PlainSelect) selectBody, (String) obj);
        } else if (selectBody instanceof SetOperationList) {
            SetOperationList setOperationList = (SetOperationList) selectBody;
            List<SelectBody> selectBodyList = setOperationList.getSelects();
            selectBodyList.forEach(s -> this.setWhere((PlainSelect) s, (String) obj));
        }
    }

    /**
     * 设置 where 条件
     *
     * @param plainSelect  查询对象
     * @param whereSegment 查询条件片段
     */
    protected void setWhere(PlainSelect plainSelect, String whereSegment) {
        Expression sqlSegment = dataPermissionHandler.getSqlSegment(plainSelect.getWhere(), whereSegment);
        if (null != sqlSegment) {
            plainSelect.setWhere(sqlSegment);
        }
    }
}

二、使用案例

mybatis-plus在gitee的仓库中，有人询问了如何使用DataPermissionInterceptor，下面有人给出了例子，一共分为两步，一是实现dataPermissionHandler接口，二是将实现添加到mybstis-plus的处理器中。他的例子中是根据不同权限类型拼接sql。

通用的方案是在所有的表中增加权限相关的字段，如部门、门店、租户等。实现dataPermissionHandler接口时较方便，可直接添加这几个字段的条件，无需查询数据库。

/**
 * 自定义数据权限
 *
 * @Author PXL
 * @Version 1.0
 * @Date 2021-02-07 16:52
 */
public class DataPermissionHandlerImpl implements DataPermissionHandler {

    @Override
    public Expression getSqlSegment(Expression where, String mappedStatementId) {
        try {
            Class<?> clazz = Class.forName(mappedStatementId.substring(0, mappedStatementId.lastIndexOf(".")));
            String methodName = mappedStatementId.substring(mappedStatementId.lastIndexOf(".") + 1);
            Method[] methods = clazz.getDeclaredMethods();
            for (Method method : methods) {
                DataPermission annotation = method.getAnnotation(DataPermission.class);
                if (ObjectUtils.isNotEmpty(annotation) && (method.getName().equals(methodName) || (method.getName() + "_COUNT").equals(methodName))) {
                    // 获取当前的用户
                    LoginUser loginUser = SpringUtils.getBean(TokenService.class).getLoginUser(ServletUtils.getRequest());
                    if (ObjectUtils.isNotEmpty(loginUser) && ObjectUtils.isNotEmpty(loginUser.getUser()) && !loginUser.getUser().isAdmin()) {
                        return dataScopeFilter(loginUser.getUser(), annotation.value(), where);
                    }
                }
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return where;
    }


    /**
     * 构建过滤条件
     *
     * @param user 当前登录用户
     * @param where 当前查询条件
     * @return 构建后查询条件
     */
    public static Expression dataScopeFilter(SysUser user, String tableAlias, Expression where) {
        Expression expression = null;
        for (SysRole role : user.getRoles()) {
            String dataScope = role.getDataScope();
            if (DataScopeAspect.DATA_SCOPE_ALL.equals(dataScope)) {
                return where;
            }
            if (DataScopeAspect.DATA_SCOPE_CUSTOM.equals(dataScope)) {
                InExpression inExpression = new InExpression();
                inExpression.setLeftExpression(buildColumn(tableAlias, "dept_id"));
                SubSelect subSelect = new SubSelect();
                PlainSelect select = new PlainSelect();
                select.setSelectItems(Collections.singletonList(new SelectExpressionItem(new Column("dept_id"))));
                select.setFromItem(new Table("sys_role_dept"));
                EqualsTo equalsTo = new EqualsTo();
                equalsTo.setLeftExpression(new Column("role_id"));
                equalsTo.setRightExpression(new LongValue(role.getRoleId()));
                select.setWhere(equalsTo);
                subSelect.setSelectBody(select);
                inExpression.setRightExpression(subSelect);
                expression = ObjectUtils.isNotEmpty(expression) ? new OrExpression(expression, inExpression) : inExpression;
            }
            if (DataScopeAspect.DATA_SCOPE_DEPT.equals(dataScope)) {
                EqualsTo equalsTo = new EqualsTo();
                equalsTo.setLeftExpression(buildColumn(tableAlias, "dept_id"));
                equalsTo.setRightExpression(new LongValue(user.getDeptId()));
                expression = ObjectUtils.isNotEmpty(expression) ? new OrExpression(expression, equalsTo) : equalsTo;
            }
            if (DataScopeAspect.DATA_SCOPE_DEPT_AND_CHILD.equals(dataScope)) {
                InExpression inExpression = new InExpression();
                inExpression.setLeftExpression(buildColumn(tableAlias, "dept_id"));
                SubSelect subSelect = new SubSelect();
                PlainSelect select = new PlainSelect();
                select.setSelectItems(Collections.singletonList(new SelectExpressionItem(new Column("dept_id"))));
                select.setFromItem(new Table("sys_dept"));
                EqualsTo equalsTo = new EqualsTo();
                equalsTo.setLeftExpression(new Column("dept_id"));
                equalsTo.setRightExpression(new LongValue(user.getDeptId()));
                Function function = new Function();
                function.setName("find_in_set");
                function.setParameters(new ExpressionList(new LongValue(user.getDeptId()) , new Column("ancestors")));
                select.setWhere(new OrExpression(equalsTo, function));
                subSelect.setSelectBody(select);
                inExpression.setRightExpression(subSelect);
                expression = ObjectUtils.isNotEmpty(expression) ? new OrExpression(expression, inExpression) : inExpression;
            }
            if (DataScopeAspect.DATA_SCOPE_SELF.equals(dataScope)) {
                EqualsTo equalsTo = new EqualsTo();
                equalsTo.setLeftExpression(buildColumn(tableAlias, "create_by"));
                equalsTo.setRightExpression(new StringValue(user.getUserName()));
                expression = ObjectUtils.isNotEmpty(expression) ? new OrExpression(expression, equalsTo) : equalsTo;
            }
        }
        return ObjectUtils.isNotEmpty(where) ? new AndExpression(where, new Parenthesis(expression)) : expression;
    }

    /**
     * 构建Column
     *
     * @param tableAlias 表别名
     * @param columnName 字段名称
     * @return 带表别名字段
     */
    public static Column buildColumn(String tableAlias, String columnName) {
        if (StringUtils.isNotEmpty(tableAlias)) {
            columnName = tableAlias + "." + columnName;
        }
        return new Column(columnName);
    }
}

// 自定义数据权限
interceptor.addInnerInterceptor(new DataPermissionInterceptor(new DataPermissionHandlerImpl()));

尝试验证

DataPermissionHandler 接口

可以看到DataPermissionHandler 接口使用中，传递来的参数是什么。

@InterceptorIgnore注解

拦截忽略注解 @InterceptorIgnore

实践应用

在维修小程序中，我使用了此方案。如下是我的代码：

/**
 * @ClassName MyDataPermissionHandler
 * @Description 自定义数据权限处理
 * @Author FangCheng
 * @Date 2022/4/2 14:54
 **/
@Component
public class MyDataPermissionHandler implements DataPermissionHandler {
    @Autowired
    @Lazy
    private UserRepository userRepository;

    @Override
    public Expression getSqlSegment(Expression where, String mappedStatementId) {
        try {
            Class<?> clazz = Class.forName(mappedStatementId.substring(0, mappedStatementId.lastIndexOf(".")));
            String methodName = mappedStatementId.substring(mappedStatementId.lastIndexOf(".") + 1);
            Method[] methods = clazz.getDeclaredMethods();
            for (Method method : methods) {
                if (!methodName.equals(method.getName())) {
                    continue;
                }
                // 获取自定义注解，无此注解则不控制数据权限
                CustomDataPermission annotation = method.getAnnotation(CustomDataPermission.class);
                if (annotation == null) {
                    continue;
                }
                // 自定义的用户上下文，获取到用户的id
                ContextUserDetails contextUserDetails = UserDetailsContextHolder.getContextUserDetails();
                String userId = contextUserDetails.getId();
                User user = userRepository.selectUserById(userId);
                // 如果是特权用户，不控制数据权限
                if (Constants.ADMIN_RULE == user.getAdminuser()) {
                    return where;
                }
                // 员工用户
                if (UserTypeEnum.USER_TYPE_EMPLOYEE.getCode().equals(user.getUsertype())) {
                	// 员工用户的权限字段
                    String field = annotation.field().getValue();
                    // 单据类型
                    String billType = annotation.billType().getFuncno();
                    // 操作类型
                    OperationTypeEnum operationType = annotation.operation();
                    // 权限字段为空则为不控制数据权限
                    if (StringUtils.isNotEmpty(field)) {
                        List<DataPermission> dataPermissions = userRepository.selectUserFuncnoDataPermission(userId, billType);
                        if (dataPermissions.size() == 0) {
                            // 没数据权限，但有功能权限则取所有数据
                            return where;
                        }
                        // 构建in表达式
                        InExpression inExpression = new InExpression();
                        inExpression.setLeftExpression(new Column(field));
                        List<Expression> conditions = null;
                        switch(operationType) {
                            case SELECT:
                                conditions = dataPermissions.stream().map(res -> new StringValue(res.getStkid())).collect(Collectors.toList());
                                break;
                            case INSERT:
                                conditions = dataPermissions.stream().filter(DataPermission::isAddright).map(res -> new StringValue(res.getStkid())).collect(Collectors.toList());
                                break;
                            case UPDATE:
                                conditions = dataPermissions.stream().filter(DataPermission::isModright).map(res -> new StringValue(res.getStkid())).collect(Collectors.toList());
                                break;
                            case APPROVE:
                                conditions = dataPermissions.stream().filter(DataPermission::isCheckright).map(res -> new StringValue(res.getStkid())).collect(Collectors.toList());
                                break;
                            default:
                                break;
                        }
                        if (conditions == null) {
                            return where;
                        }
                        conditions.add(new StringValue(Constants.ALL_STORE));
                        ItemsList itemsList = new ExpressionList(conditions);
                        inExpression.setRightItemsList(itemsList);
                        if (where == null) {
                            return inExpression;
                        }
                        return new AndExpression(where, inExpression);

                    } else {
                        return where;
                    }
                } else {
               		 // 供应商用户的权限字段
                    String field = annotation.vendorfield().getValue();
                    if (StringUtils.isNotEmpty(field)) {
                    	// 供应商如果控制权限，则只能看到自己的单据。直接使用EqualsTo 
                        EqualsTo equalsTo = new EqualsTo();
                        equalsTo.setLeftExpression(new Column(field));
                        equalsTo.setRightExpression(new StringValue(userId));
                        if (where == null) {
                            return equalsTo;
                        }
                        // 创建 AND 表达式 拼接Where 和 = 表达式
                        return new AndExpression(where, equalsTo);
                    } else {
                        return where;
                    }
                }
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return where;
    }
}

/**
 * @ClassName MybatisConfig
 * @Description mybatis配置
 * @Author FangCheng
 * @Date 2022/4/2 15:32
 **/
@Configuration
public class MybatisConfig {
    @Autowired
    private MyDataPermissionHandler myDataPermissionHandler;
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();

        // 添加数据权限插件
        DataPermissionInterceptor dataPermissionInterceptor = new DataPermissionInterceptor();
        // 添加自定义的数据权限处理器
        dataPermissionInterceptor.setDataPermissionHandler(myDataPermissionHandler);
        interceptor.addInnerInterceptor(dataPermissionInterceptor);
        // 分页插件
        //interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.SQL_SERVER));
        return interceptor;
    }
}

因为维修小程序相当于一个外挂程序，他的权限控制延用了七八年前程序的方案，设计的较为复杂，也有现成获取数据的存储过程供我们使用，此处做了一些特殊处理。增加了自定义注解、dataPermissionHandler接口实现类查询了数据库调用存储过程获取权限信息等。

自定义注解

/**
 * @ClassName CustomDataPermission
 * @Description 自定义数据权限注解
 * @Author FangCheng
 * @Date 2022/4/6 10:24
 **/
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface CustomDataPermission {
    PermissionFieldEnum field();
    PermissionFieldEnum vendorfield();
    BillTypeEnum billType();
    OperationTypeEnum operation();
}

使用注解

/**
 * @ClassName ApplyHMapper
 * @Description 维修申请单主表
 * @Author FangCheng
 * @Date 2022/4/6 13:06
 **/
@Mapper
public interface ApplyHMapper extends BaseMapper<ApplyHPo> {
    /**
     * @Description:
     * @author FangCheng
     * @Date: 2022/4/1 15:26
     * @methodName selectApplyHs
     */
    @CustomDataPermission(field = PermissionFieldEnum.FIELD_STKID,
            vendorfield = PermissionFieldEnum.FIELD_EMPTY,
            billType = BillTypeEnum.APPLY_BILL,
            operation = OperationTypeEnum.SELECT)
    Page<ApplyHPo> selectApplyHs(IPage<ApplyHPo> page, @Param(Constants.WRAPPER) QueryWrapper<ApplyHPo> queryWrapper);

    /**
     * @Description:
     * @author FangCheng
     * @Date: 2022/4/1 15:26
     * @methodName selectApplyHsForVendor
     */
    Page<ApplyHPo> selectApplyHsForVendor(IPage<ApplyHPo> page, @Param("vendorid") String vendorid, @Param(Constants.WRAPPER) QueryWrapper<ApplyHPo> queryWrapper);

    /**
     * @Description:
     * @author FangCheng
     * @Date: 2022/4/1 15:26
     * @methodName selectApplyH
     */
    @CustomDataPermission(field = PermissionFieldEnum.FIELD_STKID,
            vendorfield = PermissionFieldEnum.FIELD_EMPTY,
            billType = BillTypeEnum.APPLY_BILL,
            operation = OperationTypeEnum.SELECT)
    ApplyHPo selectApplyH(@Param("billNo") String billNo);

    /**
     * @Description:
     * @author FangCheng
     * @Date: 2022/4/1 15:26
     * @methodName selectApplyH
     */
    @InterceptorIgnore
    ApplyHPo selectApplyHNoPermission(@Param("billNo") String billNo);

    /**
     * @Description:
     * @author FangCheng
     * @Date: 2022/4/1 15:26
     * @methodName saveApplyH
     */
    void saveApplyH(ApplyHPo applyHPo);
}

最终的效果

2022-04-24 09:14:52.878 DEBUG 29254 --- [nio-8086-exec-2] c.y.w.i.p.m.ApplyHMapper.selectApplyHs   : ==> select * from t_mt_apply_h WHERE stkid IN ('0025', 'all')

总结

以上就是今天要讲的内容，本文仅仅简单介绍了Mybatis-plus数据权限接口DataPermissionInterceptor的一种实现方式，没有过多的深入研究。

部分内容参考：
Mybatis-Plus入门系列(3)- MybatisPlus之数据权限插件DataPermissionInterceptor
@InterceptorIgnore