我在我的项目中使用mybatis来执行sql查询。我需要在执行之前拦截 sql 查询以动态应用一些更改。我读过这样的@Interseptors:

@Intercepts({@Signature(type= Executor.class, method = "query", args = {...})}) 
public class ExamplePlugin implements Interceptor { 
  public Object intercept(Invocation invocation) throws Throwable { 
    return invocation.proceed(); 
  } 
  public Object plugin(Object target) { 
    return Plugin.wrap(target, this); 
  } 
  public void setProperties(Properties properties) { 
  } 
} 

它确实拦截了执行，但是没有办法更改 sql 查询，因为适当的字段不可写。我应该手动构建整个对象的新实例来替换 sql 查询吗？拦截查询执行以动态更改它的正确位置在哪里？谢谢。

请您参考如下方法:

希望对你有所帮助

@Intercepts( { @Signature(type = Executor.class, method = "query", args = { 
        MappedStatement.class, Object.class, RowBounds.class, 
        ResultHandler.class 
    }) 
}) 
public class SelectCountSqlInterceptor2 implements Interceptor 
{ 
    public static String COUNT = "_count"; 
    private static int MAPPED_STATEMENT_INDEX = 0; 
    private static int PARAMETER_INDEX = 1; 
    @Override 
    public Object intercept(Invocation invocation) throws Throwable 
    { 
        processCountSql(invocation.getArgs()); 
        return invocation.proceed(); 
    } 
    @SuppressWarnings("rawtypes") 
    private void processCountSql(final Object[] queryArgs) 
    { 
        if (queryArgs[PARAMETER_INDEX] instanceof Map) 
        { 
            Map parameter = (Map) queryArgs[PARAMETER_INDEX]; 
            if (parameter.containsKey(COUNT)) 
            { 
                MappedStatement ms = (MappedStatement) queryArgs[MAPPED_STATEMENT_INDEX]; 
                BoundSql boundSql = ms.getBoundSql(parameter); 
                String sql = ms.getBoundSql(parameter).getSql().trim(); 
                BoundSql newBoundSql = new BoundSql(ms.getConfiguration(), 
                                                    getCountSQL(sql), boundSql.getParameterMappings(), 
                                                    boundSql.getParameterObject()); 
                MappedStatement newMs = copyFromMappedStatement(ms, 
                                        new OffsetLimitInterceptor.BoundSqlSqlSource(newBoundSql)); 
                queryArgs[MAPPED_STATEMENT_INDEX] = newMs; 
            } 
        } 
    } 
    // see: MapperBuilderAssistant 
    @SuppressWarnings({ "unchecked", "rawtypes" }) 
    private MappedStatement copyFromMappedStatement(MappedStatement ms, 
            SqlSource newSqlSource) 
    { 
        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()); 
        // setStatementTimeout() 
        builder.timeout(ms.getTimeout()); 
        // setParameterMap() 
        builder.parameterMap(ms.getParameterMap()); 
        // setStatementResultMap() 
        List<ResultMap> resultMaps = new ArrayList<ResultMap>(); 
        String id = "-inline"; 
        if (ms.getResultMaps() != null) 
        { 
            id = ms.getResultMaps().get(0).getId() + "-inline"; 
        } 
        ResultMap resultMap = new ResultMap.Builder(null, id, Long.class, 
                new ArrayList()).build(); 
        resultMaps.add(resultMap); 
        builder.resultMaps(resultMaps); 
        builder.resultSetType(ms.getResultSetType()); 
        // setStatementCache() 
        builder.cache(ms.getCache()); 
        builder.flushCacheRequired(ms.isFlushCacheRequired()); 
        builder.useCache(ms.isUseCache()); 
        return builder.build(); 
    } 
    private String getCountSQL(String sql) 
    { 
        String lowerCaseSQL = sql.toLowerCase().replace("\n", " ").replace("\t", " "); 
        int index = lowerCaseSQL.indexOf(" order "); 
        if (index != -1) 
        { 
            sql = sql.substring(0, index); 
        } 
        return "SELECT COUNT(*) from ( select 1 as col_c " + sql.substring(lowerCaseSQL.indexOf(" from "))  + " )   cnt"; 
    } 
    @Override 
    public Object plugin(Object target) 
    { 
        return Plugin.wrap(target, this); 
    } 
    @Override 
    public void setProperties(Properties properties) 
    { 
    } 
}