Extending Spring form tags

• 2018/08/24

Extending form tags

• Every form tag checks its binding (via the path attribute). If the model has no data bound to that path, you get a binding error.
• Most classes call resolveId, which automatically generates the id attribute tied to the path when rendering HTML.
• If you do not want an id (e.g., to avoid JS hooks), override resolveId and return null when no explicit value is provided.

Building conditional tags

Override writeTagContent inside your tag class and return whether to evaluate the body. That is how you implement conditional logic.

Outputting raw text without TagWriter

Not recommended, but if you must render raw text, skip TagWriter. Spring tags inherit PageContext, so you can write directly via JspWriter:

this.pageContext.getOut().print("text")

Other tips

• You can grab the request from pageContext.
• After creating a custom tag, declare it in a TLD with the class’s fully qualified name (place the TLD under WEB-INF).
• Add a taglib directive in any JSP that uses the custom tag.