tobago-example/tobago-example-demo/src/main/webapp/content/30-concept/06-validation/01/JSR_303.xhtml

<?xml version="1.0" encoding="UTF-8"?>

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<ui:composition template="/main.xhtml"
                xmlns="http://www.w3.org/1999/xhtml"
                xmlns:tc="http://myfaces.apache.org/tobago/component"
                xmlns:ui="http://xmlns.jcp.org/jsf/facelets">

  <p>Tobago has JSR 303 Validation support.
    With it, you can describe the validation in an annotation in the controller.</p>

  <tc:section label="Required">
    <p>In this example, the input cannot be empty - in other words, it's required.
      The value in the controller is annotated with <code class="language-java">@NotNull</code>.</p>
    <demo-highlight language="markup">&lt;tc:in label="Input" value="\#{validationJsr303Controller.required}"/></demo-highlight>
    <demo-highlight language="java">@NotNull
private String required;</demo-highlight>
    <tc:form id="required">
      <tc:in id="in1" label="Input (required)" value="#{validationJsr303Controller.required}"/>
      <tc:button id="submit1" label="Submit"/>
    </tc:form>
  </tc:section>

  <tc:section label="Length">
    <p>The length of the given string must be between 2 and 4 characters.</p>
    <demo-highlight language="markup">&lt;tc:in label="Input" value="\#{validationJsr303Controller.length}"/></demo-highlight>
    <demo-highlight language="java">@Size(min = 2, max = 4, message = "Length must be between 2 and 4")
private String length;</demo-highlight>
    <tc:form id="length">
      <tc:in id="in2" label="2 to 4 Character" value="#{validationJsr303Controller.length}"/>
      <tc:button id="submit2" label="Submit"/>
    </tc:form>
  </tc:section>
</ui:composition>