Although both <c:set> and <jsp:useBean> create or work with variables/objects in JSP,
they have very different purposes and work at different levels.

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🔵 1. <jsp:useBean>

Feature	Explanation
Purpose	To create or locate a JavaBean (Java class instance)
Scope	Page, request, session, or application (specified explicitly)
Target	JavaBeans (classes with getters/setters)
Behavior	If the bean doesn’t exist in scope, it creates a new one.
Tag	Built-in JSP Action tag (jsp:useBean)

✅ Used when you need an object instance (typically of a JavaBean) to hold structured data.

Example:

<jsp:useBean id="user" class="com.example.User" scope="session" />
<jsp:setProperty name="user" property="name" value="Stanley" />

Creates or reuses a User object and stores it in session scope.

User must have a public no-argument constructor.

🔵 2. <c:set>

Feature	Explanation
Purpose	To set a value (any object, simple value, or result of an expression) into a variable.
Scope	Page, request, session, or application (default is page scope)
Target	Any variable (String, Integer, JavaBean, Map, etc.)
Behavior	Always sets a value; does not create a new instance automatically.
Tag	Part of JSTL Core (c prefix)

✅ Used for assigning values or overwriting variables easily.

Example:

<c:set var="username" value="Stanley" scope="session" />

Simply sets "Stanley" into sessionScope.username.

✅ It can also modify JavaBean properties:

<c:set target="${user}" property="name" value="Stanley" />

Equivalent to user.setName("Stanley");

🛠️ Key Differences Table

Feature	<jsp:useBean>	<c:set>
Creates new object?	✅ Yes (if object not found in scope)	❌ No, just sets a value
Main use	Create or find a JavaBean	Set a variable or update property
Target	JavaBean class	Any object, String, Number, Collection, Map, Bean property
Part of	JSP Action Tags (jsp)	JSTL Core (c)
Scope management	Must specify explicitly in tag (optional)	Default is pageScope, but can specify others
Dependency	Needs a real Java class with getters/setters	No special class needed

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🎯 In short:

If you need…	Use…
To create or find a JavaBean instance	<jsp:useBean>
To set or update a simple variable or a bean property	<c:set>

📢 Real-World Example Together

Example JSP:

<jsp:useBean id="user" class="com.example.User" scope="session" />
<c:set target="${user}" property="name" value="Stanley" />
<p>Hello, ${user.name}!</p>

useBean ensures there is a User object.

c:set sets the name property.

EL ${user.name} reads it.