如何在组件的 value 属性中使用“<”[重复]

当我尝试命名我的a4j:commandButton按价值<<
像那样

<a4j:commandButton id="myButton" 
    value="<<"
    render="myGrid"
    styleClass="style_btn"
    disabled="false" />

发生错误

我的调试轨迹

Error Traced[line: 88] The value of attribute "value" associated with an element type "null" must not contain the '<' character.] with root cause
javax.faces.view.facelets.FaceletException: Error Parsing /screens/s1.xhtml: Error Traced[line: 88] The value of attribute "value" associated with an element type "null" must not contain the '<' character.
    at com.sun.faces.facelets.compiler.SAXCompiler.doCompile(SAXCompiler.java:390)
    at com.sun.faces.facelets.compiler.SAXCompiler.doCompile(SAXCompiler.java:364)

Use XML/HTML 实体 http://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references插入< or >在 XML 文件中：

value="<<"