MyBatis 自定义 SQL 拦截器，2021腾讯Java面试题精选

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@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(Pro

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perties 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) {

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