Call Java Class in JSP

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1. Overview

When working with JSP (JavaServer Pages), we often need to invoke backend logic directly from our JSP files. Whether we’re accessing business logic, performing calculations, or retrieving data from a service layer, knowing how to call a Java class in JSP is essential.

In this tutorial, we’ll explore two approaches to doing this cleanly and effectively.

2. Introduction to the Problem

Before we dive into the code, let’s understand the motivation.

As JSPs are meant to focus on presentation (View layer in MVC), sometimes calling a Java class is necessary, especially in small projects or legacy applications. For example, in a JSP file, we may want to:

Perform backend computations
Reuse some utility methods
Access beans or business logic
Avoid writing too much Java code directly inside JSP etc.

In this tutorial, we’ll learn two approaches to achieve the goal.

Next, let’s dive in.

3. Using JSP Scriptlets

First, let’s look at a simple Java class:

public class CourseWelcome {
    public String greeting(String username) {
        return String.format("Hi %s, how are you doing?", username);
    }

    public static String staticWelcome(String courseName) {
        return String.format("Welcome to Baeldung's %s course", courseName);
    }
}

In the CourseWelcome class, we have two methods:

greeting() – An instance method to return a greeting String message
staticWelcome() – A static method to return a welcome String message

Next, let’s see how to call these two methods from a JSP page.

In this tutorial, we’ll use Spring Boot to navigate our JSP pages. For example, we can create a controller and an HTTP mapping:

@Controller
@RequestMapping("/course")
public class WelcomeController {
    @GetMapping("/welcome")
    public String greetingAndWelcome() {
        return "course/welcome";
    }
}

For simplicity, we’ll skip the Spring MVC configurations.

Next, let’s use JSP scriptlets in the course/welcome.jsp file to call the two methods defined in CourseWelcome:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="com.baeldung.boot.jsp.coursewelcome.CourseWelcome" %>
<html>
<head>
    <title>Welcome to Course</title>
</head>
<body>
    <%
        CourseWelcome courseWelcomeObj = new CourseWelcome();
    %>
    <div><%= courseWelcomeObj.greeting("Kai")%></div>
    <div><%= CourseWelcome.staticWelcome("Spring Boot")%></div>
</body>
</html>

In the above JSP file, we first import the CourseWelcome class and then wrap the Java code to create a CourseWelcome object between JSP scriptlet tags ‘<%‘ and ‘%>‘.

We can invoke CourseWelcome‘s static and object methods and display the result using JSP expression tags (<%= … %>).

Now, let’s start the Spring Boot application and open the page in our browser:

As we can see, we got the expected result on the page.

4. Using the <jsp:useBean> Action

Alternatively, we can call a Java class using the <jsp:useBean> action.

4.1. Calling the CourseWelcome Class

Let’s create a new JSP file course/welcome-usebean.jsp to call CourseWelcome‘s methods:

<html>
<head>
    <title>Welcome to Course</title>
</head>
<body>
    <p>Using jsp:useBean action</p>
    <jsp:useBean id="welcomeBean" class="com.baeldung.boot.jsp.coursewelcome.CourseWelcome"/>
    <div>
        <%= welcomeBean.greeting("Kevin")%>
    </div>
    <div>
        <%= com.baeldung.boot.jsp.coursewelcome.CourseWelcome.staticWelcome("Java Collections")%>
    </div>
</body>
</html>

As the JSP file shows, in the <jsp:useBean> tag, we defined an id, a reference to the JavaBean instance. In this example, it’s welcomeBean. Also, we need to specify the qualified class name of the bean class. Then, we can call CourseWelcome‘s object methods via the bean name defined as id, for example, welcomeBean.greeting().

However, we must note that we cannot invoke a class’s static methods using <jsp:useBean>. Therefore, we still need to access a class’s static resources between JSP scriptlets or JSP expression tags.

Next, let’s add a mapping method in WelcomeController to point to our newly created JSP file:

@Controller
@RequestMapping("/course")
public class WelcomeController {
    // ... same code is omitted
    @GetMapping("/welcome-usebean")
    public String greetingAndWelcomeUseBean() {
        return "course/welcome-usebean";
    }
}

Now, let’s start the application and verify if the JSP file works:

The screenshot shows that the JSP file’s <jsp:useBean> action works as expected.

4.2. Working With JavaBeans

As its name implies, typically we use <jsp:useBean> with JavaBeans. Usually, a JavaBean contains a set of properties, corresponding getters and setters, and a default constructor.

Next, let’s create a JavaBean class and look at how <jsp:useBean> works with it:

public class CourseWelcomeBean {
    private String username;
    private String courseName;

    //... getters and setters are omitted

    public String greetingUser() {
        return String.format("Hi %s, how do you do?", username);
    }

    public String welcomeMsg() {
        return String.format("Welcome to Baeldung's %s course!", courseName);
    }
}

The CourseWelcomeBean holds two properties and two instance methods.

Then, let’s create a new JSP file course/welcome-by-javabean.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Welcome to Course</title>
</head>
<body>
    <p>Using jsp:useBean action with a JavaBean</p>
    <jsp:useBean id="courseWelcomeBean" class="com.baeldung.boot.jsp.coursewelcome.CourseWelcomeBean"/>
    <jsp:setProperty name="courseWelcomeBean" property="username" value="Eric"/>
    <jsp:setProperty name="courseWelcomeBean" property="courseName" value="Spring Security"/>
    <div><%= courseWelcomeBean.greetingUser()%></div>
    <div><%= courseWelcomeBean.welcomeMsg()%></div>
</body>
</html>

As the code shows, after we declared a JavaBean using <jsp:useBean>, we can set the bean’s properties by <jsp:setProperty>. Also, we can call the bean’s instance methods as usual.

Finally, let’s create a mapping method in the controller and test the course/welcome-by-javabean.jsp file:

@Controller
@RequestMapping("/course")
public class WelcomeController {
    // ... same code is omitted
    @GetMapping("/welcome-by-javabean")
    public String greetingAndWelcomeByJavaBean() {
        return "course/welcome-by-javabean";
    }
}

The <jsp:useBean> action behaves as expected when used with a JavaBean.

5. Conclusion

In this article, we’ve seen two ways to call a Java class in JSP, from basic scriptlets to more structured approaches like <jsp:useBean>. As we develop more complex applications, it’s important to separate logic and view, but having this knowledge helps us when working with legacy systems or building quick prototypes.

The code backing this article is available on GitHub. Once you're logged in as a Baeldung Pro Member, start learning and coding on the project.