【log4j2日志框架】修改转储日志文件权限

谁借莪１个温暖的怀抱￠ 2022-12-15 11:05 222阅读 0赞

## 0.背景 ##

对于安全要求严格的系统，转储的压缩日志文件，要求文件权限为只读，而找遍了log4j2的资料，都没发现有这样配置，log4j2框架对于日志的默认权限都是640，无论如何也为日志文件保留可写权限，貌似无法单独为压缩后的日志配置权限。不过log4j2是支持自定义日志滚动策略的，干脆直接从源代码研究如何扩展log4j2的日志插件。

## 1.分析解决思路 ##

一般情况我们选择rolling.strategy.type的时候选择的都是DefaultRolloverStrategy，整个滚动策略的实现还是挺复杂的，我只想以最小的改动实现这个功能。DefaultRolloverStrategy核心逻辑在rollover中，该方法是在构造一个RolloverDescription的实例，观察构造RolloverDescription实例需要的参数

![在这里插入图片描述][20201021182743766.png_pic_center]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjE0MjA0Mg_size_16_color_FFFFFF_t_70_pic_center]  
最后一个参数正是压缩文件的处理类，前三个参数不用管。当我们配置的压缩日志格式为gz时，第四个参数的实现类是GzCompressAction，其核心方法execute就是在将.log文件压缩为.gz文件。整个日志的滚动策略我都不想修改，只想在GzCompressAction的execute方法之后插入一段修改压缩文件权限的方法。

## 2、扩展GzCompressAction ##

![在这里插入图片描述][20201021183828508.png_pic_center]  
GzCompressAction由final修饰无法继承，最简单的办法就是继承它的父类，并将GzCompressAction作为成员。实现execute方法时不用关系原GzCompressAction具体的逻辑，直接调用成员的execute方法，然后调用我提供的修改文件权限的方法。这样便实现我刚说的不改动原有逻辑，只在压缩后修改文件权限。

public class CustomGzCompressAction extends AbstractAction { 
        private final GzCompressAction gzCompressAction;
    
        public CustomGzCompressAction(GzCompressAction gzCompressAction) { 
            this.gzCompressAction = gzCompressAction;
        }
    
        @Override
        public boolean execute() throws IOException { 
            boolean result = gzCompressAction.execute();
            File destination = gzCompressAction.getDestination();
            if (destination != null) { 
                FilePermissionUtil.chmodLogFile(destination);
            }
            return result;
        }
    }

FilePermissionUtil

public class FilePermissionUtil { 
        private static final Logger LOG = LoggerFactory.getLogger(FilePermissionUtil.class);
    
        /** * 修改文件权限为只读 * * @param fileName 文件路径 */
        public static void chmodLogFile(File fileName) { 
            try { 
                LOG.info("change log file permission");
                Set<PosixFilePermission> perms = EnumSet.of(OWNER_READ, GROUP_READ);
                if (Files.readAttributes(fileName.toPath(), PosixFileAttributes.class) != null) { 
                    PosixFileAttributes attr = Files.readAttributes(fileName.toPath(), PosixFileAttributes.class);
                    attr.permissions().clear();
                }
                Files.setPosixFilePermissions(fileName.toPath(), perms);
            } catch (FileNotFoundException e) { 
                LOG.error("file nod found ,fileName={}", fileName);
            } catch (IOException e) { 
                LOG.error("change file permission error", e);
            }
        }
    }

## 3、扩展DefaultRolloverStrategy ##

由于log4j2是以插件的形式加载滚动策略的，因此我们要像DefaultRolloverStrategy一样将自定义的滚动策略定义为一个插件。这里直接将DefaultRolloverStrategy的代码拷贝过来，利用DefaultRolloverStrategy的实例构造CustomRolloverStrategy。

@Plugin(name = "CustomRolloverStrategy", category = Core.CATEGORY_NAME, printObject = true)
    public class CustomRolloverStrategy extends DefaultRolloverStrategy { 
        private static final Logger LOG = LoggerFactory.getLogger(CustomRolloverStrategy.class);
    
        protected CustomRolloverStrategy(int minIndex, int maxIndex,
                                        boolean useMax, int compressionLevel,
                                        StrSubstitutor strSubstitutor, Action[] customActions,
                                        boolean stopCustomActionsOnError,
                                        String tempCompressedFilePatternString) { 
            super(minIndex, maxIndex, useMax,
                    compressionLevel, strSubstitutor,
                    customActions, stopCustomActionsOnError,
                    tempCompressedFilePatternString);
        }
    
        protected CustomRolloverStrategy(
                int minIndex, int maxIndex, boolean useMax,
                int compressionLevel, StrSubstitutor strSubstitutor,
                Action[] customActions, boolean stopCustomActionsOnError) { 
            super(minIndex, maxIndex, useMax,
                    compressionLevel, strSubstitutor,
                    customActions, stopCustomActionsOnError);
        }
    
        /** * Strateg的构造factory * * @param max 最大文件个数 * @param min 最小文件个数 * @param fileIndex 最大文件索引 * @param compressionLevelStr 压缩等级 * @param customActions 自定义Action * @param stopCustomActionsOnError 自定义Action发生错误时是否停止 * @param config 其他配置 * @return CustomRolloverStrategy */
        @PluginFactory
        public static CustomRolloverStrategy createStrategy(
                // @formatter:off
                @PluginAttribute("max") final String max,
                @PluginAttribute("min") final String min,
                @PluginAttribute("fileIndex") final String fileIndex,
                @PluginAttribute("compressionLevel") final String compressionLevelStr,
                @PluginElement("Actions") final Action[] customActions,
                @PluginAttribute(value = "stopCustomActionsOnError",
                        defaultBoolean = true)
                final boolean stopCustomActionsOnError,
                @PluginConfiguration final Configuration config) { 
            DefaultRolloverStrategy defaultRolloverStrategy = DefaultRolloverStrategy.newBuilder()
                    .withMin(min)
                    .withMax(max)
                    .withFileIndex(fileIndex)
                    .withCompressionLevelStr(compressionLevelStr)
                    .withCustomActions(customActions)
                    .withStopCustomActionsOnError(stopCustomActionsOnError)
                    .withConfig(config)
                    .build();
            CustomRolloverStrategy customRolloverStrategy
                    = new CustomRolloverStrategy(defaultRolloverStrategy.getMinIndex(),
                    defaultRolloverStrategy.getMaxIndex(), defaultRolloverStrategy.isUseMax(),
                    defaultRolloverStrategy.getCompressionLevel(),
                    defaultRolloverStrategy.getStrSubstitutor(),
                    customActions, defaultRolloverStrategy.isStopCustomActionsOnError());
            return customRolloverStrategy;
        }
    
        /** * 重写的DefaultRolloverStrategy的rollover * * @param manager manager * @return RolloverDescription * @throws SecurityException */
        @Override
        public RolloverDescription rollover(RollingFileManager manager) throws SecurityException { 
            RolloverDescription result = super.rollover(manager);
            Action asynchronous = result.getAsynchronous();
            if (asynchronous instanceof GzCompressAction) { 
                asynchronous = new CustomGzCompressAction((GzCompressAction) asynchronous);
            }
    
            return new RolloverDescriptionImpl(result.getActiveFileName(), false, result.getSynchronous(), asynchronous);
        }
    
    }

rollover的实现也是调用父类的rollover，然后将父类返回对象中的asynchronous替换为我们扩展的CustomGzCompressAction，其他参数不变。

## 4、配置 ##

将log4j2.properties中的rolling.strategy.type全部替换为CustomRolloverStrategy，便实现我们要的修改压缩日志文件权限的功能。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjE0MjA0Mg_size_16_color_FFFFFF_t_70_pic_center 1]

## 5、效果 ##

记录中的日志权限为6xx，压缩后的gz为440  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjE0MjA0Mg_size_16_color_FFFFFF_t_70_pic_center 2]

[20201021182743766.png_pic_center]: /images/20221123/b3d9c122d8e14856a9c3c22d104d97ae.png
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[20201021183828508.png_pic_center]: /images/20221123/37c04285b9c74c4caf4de42edcd72659.png
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