Mybatis SQL数量限制插件的实现
目录
- 插件背景
- 插件功能
- 支持灵活配置插件
- 支持个别特殊方法插件效果不生效
- 插件代码
- 总结
插件背景
起因是一次线上事故,现有项目对数据库的操作依赖编码者自己的行为规范,有可能出现考虑不当对全表进行查询,数据量极大的情况会引发频繁GC带来一系列的问题
为了避免该问题,基于myBATis开发一个插件,默认限制查询的条数,默认开启该功能,默认1000条。插件功能
支持灵活配置插件
可以通过配置application.properties
文件中的配置,灵活控制插件,如果有接入动态配置中心,同样可以把一下配置添加进去,这样可以达到运行时灵活控制插件的效果,参数详情见上文:
mybatis.limit.size.enable
:是否开启插件功能。
mybatis.limit.size
:插件限制查询数量,如果不配置使用默认:1000条。
支持个别特殊方法插件效果不生效
该插件加载之后,默认会拦截所有查询语句,同时会过滤掉已经存在limit或者如count等统计类的sql,但是仍然有极个别业务场景需要绕开此拦截,因此提供了注解,支持在全局开启limit插件的情况下,特殊接口不走拦截。
@NotSupportDefaultLimit
-> 该注解在插件开启的情况下,可以针对某个不需要查询限制的接口单独设置屏蔽此功能
注意
现有已知的不兼容的场景:代码中使用RowBounds进行逻辑分页,接口会报错,因为mybatis的RowBounds是一次性将数据查出来,在内存中进行分页的,而mybatis插件是无法区分该种形式,也就无法兼容。插件代码
1、添加一个配置类
@Configuration @PropertySource(value = {"classpath:application.properties"},encoding = "utf-8") public class LimitProperties { /** * 默认限制数量 */ private final static int defaultLimitSize = 1000; /** * 插件的开关 */ @Value("${mybatis.limit.size.enable}") private Boolean enable; /** * 配置限制数量 */ @Value("${mybatis.limit.size}") private Integer size; public LimitProperties() { } public boolean isOffline() { return this.enable != null && !this.enable; } public int limit() { return this.size != null && this.size > 0 ? this.size : defaultLimitSize; } public void setSize(Integer size) { this.size = size; } }
2、定义SQL处理器,用来修改SQL
public class SqlHandler { private static final String LIMIT_SQL_TEMPLATE = "%s limit %s;"; private static final List<String> KEY_WORD = Arrays.asList("count", "limit", "sum", "avg", "min", "max"); private BoundSql boundSql; private String originSql; private Boolean needOverride; private String newSql; public static SqlHandler build(BoundSql boundSql, int size) { String originSql = boundSql.getSql().toLowerCase(); SqlHandler handler = new SqlHandler(boundSql, originSql); if (!containsKeyWord(handler.getOriginSql())) { handler.setNeedOverride(Boolean.TRUE); String newSql = String.format(LIMIT_SQL_TEMPLATE, originSql.replace(";", ""), size); handler.setNewSql(newSql); } return handler; } private SqlHandler(BoundSql boundSql, String originSql) { this.needOverride = Boolean.FALSE; this.boundSql = boundSql; this.originSql = originSql; } public boolean needOverride() { return this.needOverri编程客栈de; } public static boolean containsKeyWord(String sql) { Iterator var1 = KEY_WORD.iterator(); String keyWord; do { if (!var1.hasNext()) { return Boolean.FALSE; } keyWord = (String)var1.next(); } while(!sql.contains(keyWord)); return Boolean.TRUE; } public BoundSql getBoundSql() { return this.boundSql; } public void setBo编程客栈undSql(BoundSql boundSql) { this.boundSql = boundSql; } public String getOriginSql() { return this.originSql; } public void setOriginSql(String originSql) { th编程客栈is.originSql = originSql; } public Boolean getNeedOverride() { return this.neepythondOverride; } public void setNeedOverride(Boolean needOverride) { this.needOverride = needOverride; } public String getNewSql() { return this.newSql; } public void setNewSql(String newSql) { this.newSql = newSql; } }
3、第一步定义一个插件
/** * mybatis插件:查询数量限制 * 使用方法详见: * 拦截mybatis的:Executor.query() * @see Executor#query(org.apache.ibatis.mapping.MappedStatement, Java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler) * @see Executor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql) */ @Component @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 LimitInterceptor implements Interceptor { @Autowired LimitProperties limitProperties; public LimitInterceptor() { } public Object intercept(Invocation invocation) throws Throwable { if (!this.limitProperties.isOffline() && !LimitThreadLocal.isNotSupport()) { Object[] args = invocation.getArgs(); MappedStatement ms = (MappedStatement) args[0]; Object parameter = args[1]; BoundSql boundSql = args.length == 4 ? ms.getBoundSql(parameter) : (BoundSql) args[5]; SqlHandler sqlHandler = SqlHandler.build(boundSql, this.limitProperties.limit()); if (!sqlHandler.needOverride()) { return invocation.proceed(); } else { // 需要覆盖 Executor executor = (Executor) invocation.getTarget(); RowBounds rowBounds = (RowBounds) args[2]; ResultHandler resultHandler = (ResultHandler) args[3]; CacheKey cacheKey = args.length == 4 ? executor.createCacheKey(ms, parameter,www.devze.com rowBounds, boundSql) : (CacheKey) args[4]; MetaObject metaObject = SystemMetaObject.forObject(boundSql); metaObject.setValue("sql", sqlHandler.getNewSql()); return executor.query(ms, parameter, rowBounds, resultHandler, cacheKey, boundSql); } } else { return invocation.proceed(); } } public Object plugin(Object o) { return Plugin.wrap(o, this); } public void setProperties(Properties properties) { } }
4、下面定义一个注解,用来设置哪些接口不需要数量限制
@Retention(RetentionPolicy.RUNTIME) @Target({ElementType.METHOD}) @Documented public @interface NotSupportDefaultLimit { }
5、使用AOP去拦截不需要数量控制限制的接口
/** * AOP:对@NotSupportDefaultLimit进行环绕通知 * 主要作用:为当前线程set一个标志,标记当前线程不需要数量限制 */ @ASPect @Component public class LimitSupportAop { @Autowired LimitProperties limitProperties; public LimitSupportAop() { } @Around("@annotation(com.jkys.vitamin.rpc.mybatis.NotSupportDefaultLimit)") public Object around(ProceedingJoinPoint proceedingJoinPoint) throws Throwable { if (this.limitProperties.isOffline()) { return proceedingJoinPoint.proceed(); } else { Object var2; try { LimitThreadLocal.tryAcquire(); var2 = proceedingJoinPoint.proceed(); } finally { LimitThreadLocal.tryRelease(); } return var2; } } }
/** * 记录当前线程执行SQL,是否 不需要数量限制 */ public class LimitThreadLocal { private static final ThreadLocal<Integer> times = new ThreadLocal(); public LimitThreadLocal() { } public static void tryAcquire() { Integer time = (Integer)times.get(); if (time == null || time < 0) { time = 0; } times.set(time + 1); } public static void tryRelease() { Integer time = (Integer)times.get(); if (time != null && time > 0) { times.set(time - 1); } if ((Integer)times.get() <= 0) { times.remove(); } } public static boolean isSupport() { return times.get() == null || (Integer)times.get() <= 0; } public static boolean isNotSupport() { return times.get() != null && (Integer)times.get() > 0; } }
总结
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