{"id":3691,"date":"2011-08-23T16:59:12","date_gmt":"2011-08-23T14:59:12","guid":{"rendered":"http:\/\/blog.jteam.nl\/?p=3691"},"modified":"2011-08-23T16:59:12","modified_gmt":"2011-08-23T14:59:12","slug":"filtering-specific-exceptions-when-using-log4j","status":"publish","type":"post","link":"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/","title":{"rendered":"Filtering specific exceptions when using log4j"},"content":{"rendered":"

\"\"<\/a>A while ago I was working on a project where a background job was being triggered every few seconds or so. This job would call a method on a service, that connected to a remote backend, that was regularly unavailable.<\/p>\n

When the backend was down, the logs would be flooded with long stacktraces every few seconds. Making it all but impossible to spot actual errors  amid the carnage.<\/p>\n

To solve this problem I could have disabled logging for this service completely. But in this case that seemed like a bad idea. This service was, by all means and purposes a kitchen sink. By disabling logging completely I would run the risk of also swallowing legitimate errors. What I really wanted to do was filter out only this “BackendNotAvailableException”<\/p>\n

Fortunately there is a way to do that. Contained within Apache Extras Companion for Apache log4j<\/a> there is a filter called ExpressionFilter<\/a> that you can use to do exactly that. Here’s an example of how to configure it for this usecase.<\/p>\n

<br>\n&lt;?xml version="1.0" encoding="UTF-8"?&gt;<br>\n&lt;!DOCTYPE log4j:configuration SYSTEM "log4j.dtd"&gt;<br>\n&lt;log4j:configuration xmlns:log4j="http:\/\/jakarta.apache.org\/log4j\/" debug="false"&gt;<br>\n    &lt;appender name="CONSOLE"&gt;<br>\n        &lt;param name="Target" value="System.out"\/&gt;<br>\n        &lt;layout&gt;<br>\n            &lt;param name="ConversionPattern" value="%d %p [%c] - %m%n"\/&gt;<br>\n        &lt;\/layout&gt;<br>\n        &lt;filter class="org.apache.log4j.filter.ExpressionFilter"&gt;<br>\n            &lt;param name="expression" value="EXCEPTION ~= com.company.BackendNotAvailableException" \/&gt;<br>\n            &lt;param name="acceptOnMatch" value="false"\/&gt;<br>\n        &lt;\/filter&gt;<br>\n    &lt;\/appender&gt;<br>\n    &lt;root&gt;<br>\n        &lt;priority value ="INFO" \/&gt;<br>\n        &lt;appender-ref ref="CONSOLE"\/&gt;<br>\n    &lt;\/root&gt;<br>\n&lt;\/log4j:configuration&gt;<br>\n<\/pre><\/p>\n
There is actually a lot more you can do with this filter and i encourage you to check it out in greater detail<\/p>\n\n\n
\"\"<\/a><\/figure>\n","protected":false},"excerpt":{"rendered":"
A while ago I was working on a project where a background job was being triggered every few seconds or so. This job would call a method on a service, that connected to a remote backend, that was regularly unavailable. When the backend was down, the logs would be flooded with long stacktraces every few […]<\/p>\n","protected":false},"author":58,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"content-type":"","footnotes":""},"categories":[31,10],"tags":[11,191,192],"class_list":["post-3691","post","type-post","status-publish","format-standard","hentry","category-java","category-development","tag-java","tag-log4j","tag-logging"],"acf":[],"yoast_head":"\nFiltering specific exceptions when using log4j - Trifork Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Filtering specific exceptions when using log4j - Trifork Blog\" \/>\n<meta property=\"og:description\" content=\"A while ago I was working on a project where a background job was being triggered every few seconds or so. 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When the backend was down, the logs would be flooded with long stacktraces every few […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/\" \/>\n<meta property=\"og:site_name\" content=\"Trifork Blog\" \/>\n<meta property=\"article:published_time\" content=\"2011-08-23T14:59:12+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/blog.jteam.nl\/wp-content\/uploads\/2011\/08\/log4j-logo.jpg\" \/>\n<meta name=\"author\" content=\"Jelmer Kuperus\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Jelmer Kuperus\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/\",\"url\":\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/\",\"name\":\"Filtering specific exceptions when using log4j - Trifork Blog\",\"isPartOf\":{\"@id\":\"https:\/\/trifork.nl\/blog\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/#primaryimage\"},\"thumbnailUrl\":\"http:\/\/blog.jteam.nl\/wp-content\/uploads\/2011\/08\/log4j-logo.jpg\",\"datePublished\":\"2011-08-23T14:59:12+00:00\",\"author\":{\"@id\":\"https:\/\/trifork.nl\/blog\/#\/schema\/person\/c0ee9f25744015bf661fee1b797341f2\"},\"breadcrumb\":{\"@id\":\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/#primaryimage\",\"url\":\"http:\/\/blog.jteam.nl\/wp-content\/uploads\/2011\/08\/log4j-logo.jpg\",\"contentUrl\":\"http:\/\/blog.jteam.nl\/wp-content\/uploads\/2011\/08\/log4j-logo.jpg\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/trifork.nl\/blog\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Filtering specific exceptions when using log4j\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/trifork.nl\/blog\/#website\",\"url\":\"https:\/\/trifork.nl\/blog\/\",\"name\":\"Trifork Blog\",\"description\":\"Keep updated on the technical solutions Trifork is working on!\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/trifork.nl\/blog\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/trifork.nl\/blog\/#\/schema\/person\/c0ee9f25744015bf661fee1b797341f2\",\"name\":\"Jelmer Kuperus\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/trifork.nl\/blog\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/fff87cf8073c776ffcbe26326f713998?s=96&d=mm&r=g\",\"contentUrl\":\"https:\/\/secure.gravatar.com\/avatar\/fff87cf8073c776ffcbe26326f713998?s=96&d=mm&r=g\",\"caption\":\"Jelmer Kuperus\"},\"sameAs\":[\"http:\/\/www.dutchworks.nl\"],\"url\":\"https:\/\/trifork.nl\/blog\/author\/jelmer\/\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Filtering specific exceptions when using log4j - Trifork Blog","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/trifork.nl\/blog\/filtering-specific-exceptions-when-using-log4j\/","og_locale":"en_US","og_type":"article","og_title":"Filtering specific exceptions when using log4j - Trifork Blog","og_description":"A while ago I was working on a project where a background job was being triggered every few seconds or so. 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