阿里祭第1期纪要

字数统计: 1.8k字   |   阅读时长≈ 8分

第一期《阿里祭》已于2021年10月10日成功举办。

本次的清理目标为
easyexcel
arthas
fastjson
druid

相关讲解发布于 https://www.bilibili.com/video/BV1FR4y1J7zW

手记抄录如下。

0. 良好案例

0.1 良好的源代码引用

https://github.com/alibaba/arthas/blob/master/core/src/main/java/com/taobao/arthas/core/env/ConfigurablePropertyResolver.java

要点：

0.1.1. 确认原代码协议

前去源代码仓库查看LICENSE/LICENCE(.md/MD)文件，确认许可协议，选择许可协议允许的源代码引用方式

0.1.2. 对于GPL等不允许的协议的源代码

使用合法隔离技巧

0.1.3. 对于APACHE2 MIT BSD等BSD-like协议的源代码

按照license描述行事，不要违反禁忌，不要超出许可范围

BSD-like协议的一般通用禁忌：

  1. 篡改作者名（冒名）
  2. 篡改文件中的licence header（如果有）

1. easyexcel

1.1 refines

https://github.com/xenoamess-fork/easyexcel/tree/reduce_unneed_java.lang.Short_shortValue

削减一次多余的java.lang.Short#shortValue调用

https://github.com/xenoamess-fork/easyexcel/tree/reduce_unneed_indexOf

削减一次多余的java.lang.String#indexOf调用

https://github.com/xenoamess-fork/easyexcel/tree/use_Map%23computeIfAbsent

使用Map#computeIfAbsent

https://github.com/xenoamess-fork/easyexcel/tree/make_inner_class_CellFormatResultWrapper_be_static

将内部类类CellFormatResultWrapper变为内部静态类

https://github.com/xenoamess-fork/easyexcel/tree/do_not_use_String.trim().length()

不要使用String.trim().length()来判空，效率低&消耗内存高&晦涩。请使用你们从commons-lang抄来的isBlank和isNotBlank

https://github.com/xenoamess-fork/easyexcel/tree/log_with_reason_cannot_use_%7B%7D

Logger系接口，如果要传reason，message就不能使用占位

1.2 bugs

https://github.com/xenoamess-fork/easyexcel/tree/Iterable%23iterator_should_never_return_null

Iterable#iterator不应返回null

2. arthas

2.1 refines

https://github.com/xenoamess-fork/arthas/tree/refine_collection_creations

集合类创建相关优化

https://github.com/xenoamess-fork/arthas/tree/use_System%23currentTimeMillis_instead_of_new_Date().getTime()

使用System.currentTimeMillis()，而不是new Date().getTime()

https://github.com/xenoamess-fork/arthas/tree/use_generic_on_class_NoOpHandler

对类NoOpHandler添加泛型

https://github.com/xenoamess-fork/arthas/tree/simplify_condition

简化了条件判断

https://github.com/xenoamess-fork/arthas/tree/refine_error_logs

改良了错误捕捉

https://github.com/xenoamess-fork/arthas/tree/remove_unused_imports

去除未使用的import

https://github.com/xenoamess-fork/arthas/tree/use_StringBuilder_instead_of_StringBuffer_when_can

当可以的时候，使用StringBuilder而不是StringBuffer

https://github.com/xenoamess-fork/arthas/tree/use_static_inner_class_when_can

当可以的时候，使用静态内部类

https://github.com/xenoamess-fork/arthas/tree/numeric_issues

修复了数学计算中的问题

https://github.com/xenoamess-fork/arthas/tree/collection_issues

容器使用中的其他问题

https://github.com/xenoamess-fork/arthas/tree/string_concat_in_StringBuilder_append_chain

在StringBuilder调用链中使用了String拼接

https://github.com/xenoamess-fork/arthas/tree/do_NOT_create_wrapper_type_instance_when_can

能直接使用primitive type就不要包一层包装类

https://github.com/xenoamess-fork/arthas/tree/reduce_memory_use_in_Base64Command

Base64Command中的maxSizeLimit 转为static

https://github.com/xenoamess-fork/arthas/tree/reduce_memory_waste_in_UserStatUtil

减少无意义内存浪费

https://github.com/xenoamess-fork/arthas/tree/thread_safety_bug

典型错误使用volatile案例

https://github.com/xenoamess-fork/arthas/tree/use_Arrays.fill

使用Arrays中已有的方法来提高可读性（如果可以的话）

https://github.com/xenoamess-fork/arthas/tree/String_function_shortcuts

一些写法的可读性更好，性能同等或者略好的写法

2.2 bugs

https://github.com/xenoamess-fork/arthas/tree/potential_NPE_in_ArthasBootstrap

一个NPE

https://github.com/xenoamess-fork/arthas/tree/potential_NPE_in_ArthasReflectUtils

一个NPE

https://github.com/xenoamess-fork/arthas/tree/potential_NPE_in_Base64Command

一个NPE

https://github.com/xenoamess-fork/arthas/tree/potensial_NPE_in_BasicHttpAuthenticatorHandler

一个NPE

https://github.com/xenoamess-fork/arthas/tree/potential_NPE_in_Bootstrap

一个NPE

https://github.com/xenoamess-fork/arthas/tree/potensial_NPE_in_CompletionUtils

一个NPE

https://github.com/xenoamess-fork/arthas/tree/logic_bug_in_Decompiler

一个逻辑bug

https://github.com/xenoamess-fork/arthas/tree/potential_NPE_in_PackageInternalsFinder

一个NPE

https://github.com/xenoamess-fork/arthas/tree/potential_NPE_in_RedisTunnelClusterStore

一个NPE

另，一个逻辑bug：使用HashSet作为有顺序的容器

https://github.com/xenoamess-fork/arthas/tree/potential_NPE_in_TunnelSocketFrameHandler

一个NPE

https://github.com/xenoamess-fork/arthas/tree/log_with_reason_cannot_use_%7B%7D

Logger系接口，如果要传reason，message就不能使用占位

3. fastjson

3.1 refines

https://github.com/xenoamess-fork/fastjson/tree/unreached_branch_in_ASMDeserializerFactory

删除一个不可能抵达的branch

https://github.com/xenoamess-fork/fastjson/tree/unreached_branch_in_CalendarCodec

删除一个不可能抵达的branch

（我其实挺怀疑这里他们想做创建异常捕捉 结果做脑残了……如果真是这样那么这个应该进bugs ）

https://github.com/xenoamess-fork/fastjson/tree/avoid_calling_getTypeParameters()_several_times_for_one_same_class

性能问题

https://github.com/xenoamess-fork/fastjson/tree/avoid_unneeded_hasNext_call_in_TypeUtils

削除无意义操作

https://github.com/xenoamess-fork/fastjson/tree/use_arrays.fill_to_simplify_codes

简化代码

https://github.com/xenoamess-fork/fastjson/tree/StringBuilder_refines

StringBuilder相关优化

https://github.com/xenoamess-fork/fastjson/tree/use_static_inner_class_when_can

使用静态内部类

https://github.com/xenoamess-fork/fastjson/tree/delete_Cloneable_from_JSONValidator

从JSONValidator摘除Cloneable（我实在找不出不这么做的理由）

https://github.com/xenoamess-fork/fastjson/tree/fix_javadoc

修复javadoc中的一些错误

3.2 bugs

https://github.com/xenoamess-fork/fastjson/tree/should_not_throw_NPE_but_IllegalArgumentException_in_AbstractDateDeserializer.deserialize

错误类型错误，应抛出IllegalArgumentException，实际在某个特定条件下并没抛出，导致后续抛出NPE

https://github.com/xenoamess-fork/fastjson/tree/system_array_copy_to_wrong_array_in_JSONLexerBase

手残bug，传错变量了你……

4. druid

4.1 refines

https://github.com/xenoamess-fork/druid/tree/clean_unused_imports

清除无意义import

https://github.com/xenoamess-fork/druid/tree/use_StringBuilder_if_can

如果可以的话 使用StringBuilder替代StringBuffer

https://github.com/xenoamess-fork/druid/tree/remove_redunant_boxing

去除无意义装箱拆箱

https://github.com/xenoamess-fork/druid/tree/use_Objects.equals

使用Objects.equals简化代码

https://github.com/xenoamess-fork/druid/tree/merge_same_catch_blocks

合并相同的异常处理，简化代码

https://github.com/xenoamess-fork/druid/tree/use_computeIfAbsent

使用computeIfAbsent以优化性能

https://github.com/xenoamess-fork/druid/tree/use_switch_for_multiple_string_selection

使用switch进行多项String判别，以提升性能

https://github.com/xenoamess-fork/druid/tree/fix_javadocs

修复javadoc

https://github.com/xenoamess-fork/druid/tree/use_static_inner_class_when_can

当可以的时候，使用静态内部类

https://github.com/xenoamess-fork/druid/tree/use_StandardCharsets_to_avoid_forName_cost

使用StandardCharsets以去除寻找成本

https://github.com/xenoamess-fork/druid/tree/use_StringUtils.repeat

使用StringUtils.repeat

https://github.com/xenoamess-fork/druid/tree/collection_Bulk

使用容器的批量口子 提高性能

https://github.com/xenoamess-fork/druid/tree/use_print_when_no_format

没有格式的时候就不要用printf了

https://github.com/xenoamess-fork/druid/tree/delete_impossible_path_in_OrderByResolve

清理不可达代码

https://github.com/xenoamess-fork/druid/tree/delete_unused_field_Lexer.digits

清理无用的属性

https://github.com/xenoamess-fork/druid/tree/duplicated_put_in_a_same_map

map，重复赋值

https://github.com/xenoamess-fork/druid/tree/String_refines

String系优化

https://github.com/xenoamess-fork/druid/tree/unneeded_containsKey_waste

去除无意义的containsKey调用

https://github.com/xenoamess-fork/druid/tree/OracleLockTableStatement_is_a_subclass_of_SQLLockTableStatement_in_WallVisitorUtils

去除不可达分支

https://github.com/xenoamess-fork/druid/tree/impossible_to_both_be_null_and_be_SQLIntegerExpr

去除不可达分支

https://github.com/xenoamess-fork/druid/tree/simplify_conditions

清理无意义判断条件

4.2 bugs

https://github.com/xenoamess-fork/druid/tree/int_overflow

多处int溢出

https://github.com/xenoamess-fork/druid/tree/setters_in_MySqlAlterTablespaceStatement_meaningless

四个无意义的废物setter函数

https://github.com/xenoamess-fork/druid/tree/confusing_getChildren_function

令人迷惑的getChildren

https://github.com/xenoamess-fork/druid/tree/another_confusing_getChildren_function

另一个令人迷惑的getChildren

https://github.com/xenoamess-fork/druid/tree/NPE_in_DruidDataSource

一个NPE

https://github.com/xenoamess-fork/druid/tree/wrong_class_SQLServerInsertStatement_casting

错误的类型转换

https://github.com/xenoamess-fork/druid/tree/NPE_in_WallFilter

一个NPE

https://github.com/xenoamess-fork/druid/tree/NClob_is_a_subclass_of_Clob

父子类择出，逻辑判断错谬

https://github.com/xenoamess-fork/druid/tree/NPE_in_SchemaStatVisitor

一个NPE

https://github.com/xenoamess-fork/druid/tree/NPE_in_SpringStatManager

一个NPE

https://github.com/xenoamess-fork/druid/tree/Float_is_not_Double_in_SQLIntegerExpr

认为Float是Double

https://github.com/xenoamess-fork/druid/tree/NPE_in_SearchModifier

一个NPE

https://github.com/xenoamess-fork/druid/tree/NPE_in_SQLShowGrantsStatement

一个NPE

https://github.com/xenoamess-fork/druid/tree/illetal_equals_implement_in_DruidPooledPreparedStatement

不合法的equals实现

https://github.com/xenoamess-fork/druid/tree/re-implement_SQLUtils.hash

重新实现SQLUtils.hash。原方法让我感到身在动物园。

https://github.com/xenoamess-fork/druid/tree/wrong_way_to_use_Reader

经典的初学者错误使用Reader案例

https://github.com/xenoamess-fork/druid/tree/bug_in_RestoreVisitor.visit

纯bug，传错参了

https://github.com/xenoamess-fork/druid/tree/total_wrong_Schema.findFunction

完全荒谬的实现

https://github.com/xenoamess-fork/druid/tree/bug_in_ExportParameterVisitorUtils

纯bug，传错参了

https://github.com/xenoamess-fork/druid/tree/String_can_never_equals_SQLExpr

equals比较类型错谬

https://github.com/xenoamess-fork/druid/tree/SQLOpenStatement_is_subclass_of_SQLStatement

父子类择出，逻辑判断错谬

https://github.com/xenoamess-fork/druid/tree/int_cast_to_double_is_never_NaN

判断滞后bug

扫一扫，分享到微信

tag:

    缺失模块。
    1、请确保node版本大于6.2
    2、在博客根目录（注意不是yilia-plus根目录）执行以下命令：
    npm i hexo-generator-json-content --save

    3、在根目录_config.yml里添加配置： 

      jsonContent:
    meta: false
    pages: false
    posts:
      title: true
      date: true
      path: true
      text: false
      raw: false
      content: false
      slug: false
      updated: false
      comments: false
      link: false
      permalink: false
      excerpt: false
      categories: false
      tags: true

自称为XenoAmess的方术师。

为了得到【意义】而进行各种各样的修行。

Hack The Box