MyBatis自定义SQL拦截器示例详解

前言

本文主要是讲通过 mybaits 的 interceptor 的拓展点进行对 mybatis 执行 sql 之前做一个逻辑拦截实现自定义逻辑的插入执行。

适合场景：1. 比如限制数据库查询最大访问条数；2. 限制登录用户只能访问当前机构数据。

定义是否开启注解

定义是否开启注解, 主要做的一件事情就是是否添加 sql 拦截器。

// 全局开启
@retention(retentionpolicy.runtime)
@target(elementtype.type)
@documented
@import(mybatissqlinterceptorconfiguration.class)
public @interface enablesqlinterceptor {

}

// 自定义注解
@target({elementtype.method })
@retention(retentionpolicy.runtime)
public @interface datascope {

}

注册sql 拦截器

注册一个 sql 拦截器，会对符合条件的 sql 查询操作进行拦截。

public class mybatissqlinterceptorconfiguration implements applicationcontextaware {

    @override
    public void setapplicationcontext(applicationcontext applicationcontext) throws beansexception {
        sqlsessionfactory sqlsessionfactory = applicationcontext.getbean(sqlsessionfactory.class);
        sqlsessionfactory.getconfiguration().addinterceptor(new mybatisinterceptor());
    }
}

处理逻辑

在处理逻辑中，我主要是做一个简单的 limit 1 案例，如果是自己需要做其他的逻辑需要修改

@slf4j
@intercepts(
        {
                @signature(type = executor.class, method = "query", args = {mappedstatement.class, object.class, rowbounds.class, resulthandler.class}),
                @signature(type = executor.class, method = "query", args = {mappedstatement.class, object.class, rowbounds.class, resulthandler.class, cachekey.class, boundsql.class}),
        })
public class mybatisinterceptor implements interceptor {

    private static final logger logger = loggerfactory.getlogger(mybatisinterceptor.class);

    @override
    public object intercept(invocation invocation) throws throwable {
        // todo auto-generated method stub
        object[] args = invocation.getargs();
        mappedstatement ms = (mappedstatement) args[0];
        object parameter = args[1];
        rowbounds rowbounds = (rowbounds) args[2];
        resulthandler resulthandler = (resulthandler) args[3];
        executor executor = (executor) invocation.gettarget();
        cachekey cachekey;
        boundsql boundsql;
        //由于逻辑关系，只会进入一次
        if (args.length == 4) {
            //4 个参数时
            boundsql = ms.getboundsql(parameter);
            cachekey = executor.createcachekey(ms, parameter, rowbounds, boundsql);
        } else {
            //6 个参数时
            cachekey = (cachekey) args[4];
            boundsql = (boundsql) args[5];
        }
        datascope datascope = getdatascope(ms);
        if (objects.nonnull(datascope)) {
            string origsql = boundsql.getsql();
            log.info("origsql : {}", origsql);
            // 组装新的 sql
            // todo you weaving business
            string newsql = origsql + " limit 1";

            // 重新new一个查询语句对象
            boundsql newboundsql = new boundsql(ms.getconfiguration(), newsql,
                    boundsql.getparametermappings(), boundsql.getparameterobject());

            // 把新的查询放到statement里
            mappedstatement newms = newmappedstatement(ms, new boundsqlsource(newboundsql));
            for (parametermapping mapping : boundsql.getparametermappings()) {
                string prop = mapping.getproperty();
                if (boundsql.hasadditionalparameter(prop)) {
                    newboundsql.setadditionalparameter(prop, boundsql.getadditionalparameter(prop));
                }
            }

            args[0] = newms;
            if (args.length == 6) {
                args[5] = newms.getboundsql(parameter);
            }
        }
        logger.info("mybatis intercept sql:{},mapper方法是：{}", boundsql.getsql(), ms.getid());


        return invocation.proceed();
    }

    private mappedstatement newmappedstatement(mappedstatement ms, sqlsource newsqlsource) {
        mappedstatement.builder builder = new
                mappedstatement.builder(ms.getconfiguration(), ms.getid(), newsqlsource, ms.getsqlcommandtype());
        builder.resource(ms.getresource());
        builder.fetchsize(ms.getfetchsize());
        builder.statementtype(ms.getstatementtype());
        builder.keygenerator(ms.getkeygenerator());
        if (ms.getkeyproperties() != null && ms.getkeyproperties().length > 0) {
            builder.keyproperty(ms.getkeyproperties()[0]);
        }
        builder.timeout(ms.gettimeout());
        builder.parametermap(ms.getparametermap());
        builder.resultmaps(ms.getresultmaps());
        builder.resultsettype(ms.getresultsettype());
        builder.cache(ms.getcache());
        builder.flushcacherequired(ms.isflushcacherequired());
        builder.usecache(ms.isusecache());
        return builder.build();
    }


    private datascope getdatascope(mappedstatement mappedstatement) {
        string id = mappedstatement.getid();
        // 获取 class method
        string clazzname = id.substring(0, id.lastindexof('.'));
        string mappermethod = id.substring(id.lastindexof('.') + 1);

        class<?> clazz;
        try {
            clazz = class.forname(clazzname);
        } catch (classnotfoundexception e) {
            return null;
        }
        method[] methods = clazz.getmethods();

        datascope datascope = null;
        for (method method : methods) {
            if (method.getname().equals(mappermethod)) {
                datascope = method.getannotation(datascope.class);
                break;
            }
        }
        return datascope;
    }

    @override
    public object plugin(object target) {
        // todo auto-generated method stub
        logger.info("mysqlinterceptor plugin>>>>>>>{}", target);
        return plugin.wrap(target, this);
    }

    @override
    public void setproperties(properties properties) {
        // todo auto-generated method stub
        string dialect = properties.getproperty("dialect");
        logger.info("mybatis intercept dialect:>>>>>>>{}", dialect);
    }

    /**
     * 定义一个内部辅助类，作用是包装 sql
     */
    class boundsqlsource implements sqlsource {
        private boundsql boundsql;

        public boundsqlsource(boundsql boundsql) {
            this.boundsql = boundsql;
        }

        public boundsql getboundsql(object parameterobject) {
            return boundsql;
        }

    }

}

如何使用

我们在 xxxmapper 中对应的数据操作方法只要加入 @datascope 注解即可。

@mapper
public interface ordermapper {

   @select("select 1 ")
   @datascope
   intger selectone();

}

参考资料

mybatis.org/mybatis-3/z…

总结

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