CODEWITHSUNDEEP
javajspspring-mvc
JohnDoe
JohnDoe

Reputation: 89

How to get parameter from url

I'm writing very simple Spring MVC application(just started to learn). It has only one jsp page. After running this application(Im using Tomcat, not big deal) it has to show page with Hello and if I send some parameter to url(for example someURL/?name=mike) it has to be page with Hello mike

here is code

@Controller
@RequestMapping("/")
public class HelloController {
    @RequestMapping(method = RequestMethod.GET)
    public String printWelcome(@RequestParam("name") String param, ModelMap model) {
        if (param == null || param.isEmpty())
            model.addAttribute("message", "Hello");

        model.addAttribute("message", "Hello " + param);
        return "hello";
    }
}

and hello.jsp:

<html>
<body>
    <h1>${message}</h1>
</body>
</html>

The problem is if I there is not parameter in url, Hello page isnt shown, instead its error

Upvotes: 0

Views: 156

Answers (3)

JMM
JMM

Reputation: 4022

You need to change your method name to include required = false for the name parameter, otherwise it is required by default, change your method signature to the following:

public String printWelcome( @RequestParam(value = "name", required = false) String param, ModelMap model)

From the Spring documentation:

Parameters using this annotation are required by default, but you can specify that a parameter is optional by setting @RequestParam's required attribute to false (e.g., @RequestParam(value="id", required=false)). http://docs.spring.io/spring/docs/current/spring-framework-reference/html/mvc.html

Upvotes: 0

pratim_b
pratim_b

Reputation: 1200

You can set defaultValue parameter of @RequestParam. The default value to use as a fallback. Supplying a default value implicitly sets required() to false.

(@RequestParam(value = "name", defaultValue = "new value")String description)

Upvotes: 0

Sotirios Delimanolis
Sotirios Delimanolis

Reputation: 279960

The @RequestParam annotation has a required attribute which you can set to false (it is true by default).

public String printWelcome(@RequestParam(value = "name", required = false) String param, ModelMap model) {

only in this case will Spring give you a null argument to a @RequestParam annotated parameter.

Upvotes: 1

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