MyBatis Custom SQL Interceptor Example Explanation

Directory Preface Definition Enables Annotation Register an SQL interceptor Processing logic How to use Summarize

Preface

This article mainly talks about the MyBaits Interceptor extension point to MyBatis before SQL to do a logic interception to achieve custom logic insertion execution.

Suitable scenarios: 1. For example, limit the maximum number of accesses to database queries; 2. Restrict the login user's access to the current organization data.

Defines whether to turn on annotations

To define whether to open annotations, the main thing to do is whether to add SQL interceptor.

//  Global opening 
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(MyBatisSqlInterceptorConfiguration.class)
public @interface EnableSqlInterceptor {

}

//  Custom annotations 
@Target({ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
public @interface DataScope {

}

Register SQL Interceptor

Registering an SQL interceptor will intercept eligible SQL query operations.

public class MyBatisSqlInterceptorConfiguration implements ApplicationContextAware {

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SqlSessionFactory sqlSessionFactory = applicationContext.getBean(SqlSessionFactory.class);
        sqlSessionFactory.getConfiguration().addInterceptor(new MyBatisInterceptor());
    }
}

Processing logic

In the processing logic, I mainly do a simple limit 1 case, if it is their own need to do other logic needs to be modified

@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;
        // Because of the logical relationship, it will only enter 1 Times 
        if (args.length == 4) {
            //4  Parameters 
            boundSql = ms.getBoundSql(parameter);
            cacheKey = executor.createCacheKey(ms, parameter, rowBounds, boundSql);
        } else {
            //6  Parameters 
            cacheKey = (CacheKey) args[4];
            boundSql = (BoundSql) args[5];
        }
        DataScope dataScope = getDataScope(ms);
        if (Objects.nonNull(dataScope)) {
            String origSql = boundSql.getSql();
            log.info("origSql : {}", origSql);
            //  Assemble a new  sql
            // todo you weaving business
            String newSql = origSql + " limit 1";

            //  Re- new1 Query statement object 
            BoundSql newBoundSql = new BoundSql(ms.getConfiguration(), newSql,
                    boundSql.getParameterMappings(), boundSql.getParameterObject());

            //  Put the new query in the statement Li 
            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 The method is: {}", 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();
        //  Get  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);
    }

    /**
     *  Definition 1 Internal helper classes, which are used to wrap  SQL
     */
    class BoundSqlSource implements SqlSource {
        private BoundSql boundSql;

        public BoundSqlSource(BoundSql boundSql) {
            this.boundSql = boundSql;
        }

        public BoundSql getBoundSql(Object parameterObject) {
            return boundSql;
        }

    }

}

How to use

We only need to add @ DataScope annotation to the corresponding data operation method in XXXMapper.

@Mapper
public interface OrderMapper {

   @Select("select 1 ")
   @DataScope
   Intger selectOne();

}

References

mybatis. org/mybatis-3/z …

Summarize