Form validation

src/main/java/io/jenkins/plugins/sample/global_configuration/OnboardingPluginGlobalConfiguration.java

@@ -0,0 +1,39 @@
+package io.jenkins.plugins.sample.global_configuration;
+
+import hudson.Extension;
+import hudson.util.FormValidation;
+import jenkins.model.GlobalConfiguration;
+import org.jenkinsci.Symbol;
+import org.kohsuke.stapler.QueryParameter;
+
+
+@Extension
+@Symbol("OnboardingPlugin")
+public class OnboardingPluginGlobalConfiguration extends GlobalConfiguration {
+    private String name;
+    private String description;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getDescription() {
+        return description;
+    }
+
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    public FormValidation doCheckName(@QueryParameter String name) {
+        String regex = "^[a-zA-Z ]+$";
+        if (!name.matches(regex)) {
+            return FormValidation.warning("Name must contains characters & spaces");
+        }
+        return FormValidation.ok();
+    }
+}

src/main/resources/io/jenkins/plugins/sample/global_configuration/OnboardingPluginGlobalConfiguration/config.jelly

@@ -0,0 +1,11 @@
+<?jelly escape-by-default='true'?>
+<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form">
+    <f:section title="Onboarding Plugin">
+        <f:entry title="${%Name}" field="name">
+            <f:textbox checkMethod="post" />
+        </f:entry>
+        <f:entry title="${%Description}" field="description">
+            <f:textarea checkMethod="post" />
+        </f:entry>
+    </f:section>
+</j:jelly>