Thymeleaf is a Java-based templating engine that is used to generate HTML, XML, or other types of documents based on templates and data. It allows you to include expressions in your templates that are evaluated at runtime and replaced with the corresponding values.
In Thymeleaf, expression objects are used to access data and evaluate expressions within a template. They are identified by a prefix that indicates the dialect in which they are defined.
There are several built-in dialects in Thymeleaf that provide a set of expression objects and other features. Some of the most commonly used dialects are:
Standard Dialect: This is the default dialect in Thymeleaf and provides a set of expression objects for accessing data and evaluating expressions in templates.
Spring Standard Dialect: This dialect extends the Standard Dialect and adds expression objects for accessing data and functionality in a Spring-based application.
Layout Dialect: This dialect provides a set of expression objects for defining layouts and reusable template fragments in Thymeleaf templates.
Java 8 Time Dialect: This dialect provides expression objects for working with java.time objects in Thymeleaf templates.
To use an expression object in a Thymeleaf template, you need to specify the prefix of the dialect in which it is defined followed by the expression object itself. For example, to access a variable in the Standard Dialect, you can use the #{...} syntax:
<p>Hello, #{name}!</p>
In this example, the #{name} expression object accesses the name variable and is replaced with its value at runtime.
It's important to note that you can also create your own custom dialects in Thymeleaf by implementing the IDialect interface and registering the dialect with the Thymeleaf engine. This allows you to define your own expression objects and other features for use in your templates.