{"id":20536,"date":"2024-03-15T20:37:07","date_gmt":"2024-03-15T20:37:07","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/"},"modified":"2024-03-21T18:19:32","modified_gmt":"2024-03-21T18:19:32","slug":"how-does-mybatis-determine-if-a-list-is-empty-or-null","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/","title":{"rendered":"How does MyBatis determine if a list is empty or null?"},"content":{"rendered":"<p>In MyBatis, you can use the <if> tag to determine if a List is empty or null.<\/p>\n<p>The example code is as follows:<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-tag\">&lt;<span class=\"hljs-name\">select<\/span> <span class=\"hljs-attr\">id<\/span>=<span class=\"hljs-string\">\"selectUsers\"<\/span> <span class=\"hljs-attr\">resultType<\/span>=<span class=\"hljs-string\">\"User\"<\/span>&gt;<\/span>\r\n  SELECT * FROM users\r\n  WHERE id IN\r\n  <span class=\"hljs-tag\">&lt;<span class=\"hljs-name\">foreach<\/span> <span class=\"hljs-attr\">item<\/span>=<span class=\"hljs-string\">\"item\"<\/span> <span class=\"hljs-attr\">collection<\/span>=<span class=\"hljs-string\">\"ids\"<\/span> <span class=\"hljs-attr\">open<\/span>=<span class=\"hljs-string\">\"(\"<\/span> <span class=\"hljs-attr\">separator<\/span>=<span class=\"hljs-string\">\",\"<\/span> <span class=\"hljs-attr\">close<\/span>=<span class=\"hljs-string\">\")\"<\/span>&gt;<\/span>\r\n    #{item}\r\n  <span class=\"hljs-tag\">&lt;\/<span class=\"hljs-name\">foreach<\/span>&gt;<\/span>\r\n  <span class=\"hljs-tag\">&lt;<span class=\"hljs-name\">if<\/span> <span class=\"hljs-attr\">test<\/span>=<span class=\"hljs-string\">\"ids == null or ids.isEmpty()\"<\/span>&gt;<\/span>\r\n    AND 1=0\r\n  <span class=\"hljs-tag\">&lt;\/<span class=\"hljs-name\">if<\/span>&gt;<\/span>\r\n<span class=\"hljs-tag\">&lt;\/<span class=\"hljs-name\">select<\/span>&gt;<\/span>\r\n<\/code><\/pre>\n<p>In the code above, the <if> tag is used to check if ids is null or empty. If it is, the SQL will add the condition AND 1=0 to ensure that the query result is empty.<\/p>\n<p>Additionally, if you need to check if a List is empty or null in Java code, you can also do the check before passing the parameter to the SQL statement in MyBatis.<\/p>\n<p>The sample code is as follows:<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">public<\/span> List&lt;User&gt; <span class=\"hljs-title function_\">selectUsers<\/span><span class=\"hljs-params\">(List&lt;Integer&gt; ids)<\/span> {\r\n  <span class=\"hljs-keyword\">if<\/span> (ids == <span class=\"hljs-literal\">null<\/span> || ids.isEmpty()) {\r\n    <span class=\"hljs-keyword\">return<\/span> Collections.emptyList();\r\n  }\r\n  <span class=\"hljs-comment\">\/\/ \u8c03\u7528MyBatis\u7684SQL\u8bed\u53e5\u67e5\u8be2<\/span>\r\n}\r\n<\/code><\/pre>\n<p>In the above code, first check if ids is null or empty, if it is, simply return an empty List to avoid calling MyBatis SQL statements.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In MyBatis, you can use the tag to determine if a List is empty or null. The example code is as follows: &lt;select id=&#8221;selectUsers&#8221; resultType=&#8221;User&#8221;&gt; SELECT * FROM users WHERE id IN &lt;foreach item=&#8221;item&#8221; collection=&#8221;ids&#8221; open=&#8221;(&#8221; separator=&#8221;,&#8221; close=&#8221;)&#8221;&gt; #{item} &lt;\/foreach&gt; &lt;if test=&#8221;ids == null or ids.isEmpty()&#8221;&gt; AND 1=0 &lt;\/if&gt; &lt;\/select&gt; In the code above, the [&hellip;]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-20536","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>How does MyBatis determine if a list is empty or null? - Blog - Silicon Cloud<\/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:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How does MyBatis determine if a list is empty or null?\" \/>\n<meta property=\"og:description\" content=\"In MyBatis, you can use the tag to determine if a List is empty or null. The example code is as follows: &lt;select id=&quot;selectUsers&quot; resultType=&quot;User&quot;&gt; SELECT * FROM users WHERE id IN &lt;foreach item=&quot;item&quot; collection=&quot;ids&quot; open=&quot;(&quot; separator=&quot;,&quot; close=&quot;)&quot;&gt; #{item} &lt;\/foreach&gt; &lt;if test=&quot;ids == null or ids.isEmpty()&quot;&gt; AND 1=0 &lt;\/if&gt; &lt;\/select&gt; In the code above, the [&hellip;]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/\" \/>\n<meta property=\"og:site_name\" content=\"Blog - Silicon Cloud\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/SiliCloudGlobal\/\" \/>\n<meta property=\"article:published_time\" content=\"2024-03-15T20:37:07+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2024-03-21T18:19:32+00:00\" \/>\n<meta name=\"author\" content=\"Benjamin Taylor\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@SiliCloudGlobal\" \/>\n<meta name=\"twitter:site\" content=\"@SiliCloudGlobal\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Benjamin Taylor\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/\"},\"author\":{\"name\":\"Benjamin Taylor\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/#\/schema\/person\/ac801fe9549a25960ce48aa2e0a691c9\"},\"headline\":\"How does MyBatis determine if a list is empty or null?\",\"datePublished\":\"2024-03-15T20:37:07+00:00\",\"dateModified\":\"2024-03-21T18:19:32+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/\"},\"wordCount\":131,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/#organization\"},\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/\",\"url\":\"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/\",\"name\":\"How does MyBatis determine if a list is empty or null? 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- Blog - Silicon Cloud","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:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/","og_locale":"en_US","og_type":"article","og_title":"How does MyBatis determine if a list is empty or null?","og_description":"In MyBatis, you can use the tag to determine if a List is empty or null. The example code is as follows: &lt;select id=\"selectUsers\" resultType=\"User\"&gt; SELECT * FROM users WHERE id IN &lt;foreach item=\"item\" collection=\"ids\" open=\"(\" separator=\",\" close=\")\"&gt; #{item} &lt;\/foreach&gt; &lt;if test=\"ids == null or ids.isEmpty()\"&gt; AND 1=0 &lt;\/if&gt; &lt;\/select&gt; In the code above, the [&hellip;]","og_url":"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/","og_site_name":"Blog - Silicon Cloud","article_publisher":"https:\/\/www.facebook.com\/SiliCloudGlobal\/","article_published_time":"2024-03-15T20:37:07+00:00","article_modified_time":"2024-03-21T18:19:32+00:00","author":"Benjamin Taylor","twitter_card":"summary_large_image","twitter_creator":"@SiliCloudGlobal","twitter_site":"@SiliCloudGlobal","twitter_misc":{"Written by":"Benjamin Taylor","Est. reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/#article","isPartOf":{"@id":"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/"},"author":{"name":"Benjamin Taylor","@id":"https:\/\/www.silicloud.com\/blog\/#\/schema\/person\/ac801fe9549a25960ce48aa2e0a691c9"},"headline":"How does MyBatis determine if a list is empty or null?","datePublished":"2024-03-15T20:37:07+00:00","dateModified":"2024-03-21T18:19:32+00:00","mainEntityOfPage":{"@id":"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/"},"wordCount":131,"commentCount":0,"publisher":{"@id":"https:\/\/www.silicloud.com\/blog\/#organization"},"inLanguage":"en-US"},{"@type":"WebPage","@id":"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/","url":"https:\/\/www.silicloud.com\/blog\/how-does-mybatis-determine-if-a-list-is-empty-or-null\/","name":"How does MyBatis determine if a list is empty or null? 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