What do you know about creating custom JSP tags?

Custom JSP tags allow creating your own elements that encapsulate repetitive display logic or server-side behavior. This improves code readability and reusability in JSP.

The typical steps to create a custom tag are:

1. Creating a tag class — a class that implements the Tag interface or extends SimpleTagSupport, where the tag logic is described.
2. Defining a TLD file (Tag Library Descriptor) — an XML file that describes the tags, their attributes, and the associated class.
3. Including the tag library in JSP — using the <%@ taglib %> directive to include the TLD.

Example of a simple custom tag that outputs a greeting:

public class HelloTag extends SimpleTagSupport {
    private String name;

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public void doTag() throws JspException, IOException {
        getJspContext().getOut().write("Hello, " + name + "!");
    }
}

TLD file (hello.tld):

<tag>
    <name>hello</name>
    <tag-class>com.example.HelloTag</tag-class>
    <body-content>empty</body-content>
    <attribute>
        <name>name</name>
        <required>true</required>
    </attribute>
</tag>

In JSP, including and using the tag:

<%@ taglib prefix="ex" uri="/WEB-INF/hello.tld" %>
<ex:hello name="World" />

Thus, custom tags allow creating convenient and reusable components for JSP.