DEV Community: Sean Evans

Get Started with Modern Java Today: A Concise Guide

Sean Evans — Thu, 19 Dec 2024 08:47:35 +0000

Many people think Java is a verbose language. I've heard a joke that if your employer pays you by lines of code, then Java is the way to go.

With updates to Java, modern Java isn't so verbose anymore, so check it out.

If you're starting a new project, use modern Java today.

1. Use `record` instead of lombok

✅ Use record

public record User(String id, String name) {}

🙅 Instead of lombok annotations

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private String id;
    private String name;
}

🙅 And instead of getter, setter, equals(), hashCode(), toString(), and etc.

public class User {
    private String id;
    private String name;

    public User(String id, String name) {
        this.id = id;
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public void setName(String name) {
        this.name = name;
    }

    // equals(), hashCode(), toString() and etc. are omitted below.
}

2. Use `var` instead of class name

✅ Use var

var user = new User("1", "Tom");

🙅 Instead of duplicated class name

User user = new User("1", "Tom");

3. Use `STR."\{}"` instead of `+` between strings

✅ Use STR."\{}"

var firstName = "Thomas";
var lastName = "Cat";
var fullName = STR."His name is \{firstName} \{lastName}.";

🙅 Instead of + and " "

var firstName = "Thomas";
var lastName = "Cat";
var fullName = "His name is " + firstName + " " + lastName + ".";

🙅 And instead of new StringBuilder() and append()

var firstName = "Thomas";
var lastName = "Cat";

StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append("His name is ").append(firstName).append(" ").append(lastName).append(".");

var fullName = stringBuilder.toString();

4. Use `"""` instead of `"\n"+` between multiline strings

✅ Use """

var html = """
    <html>
    <body>
      <p>Hello World!</p>
    </body>
    </html>
    """;

🙅 Instead of "\n" and +

var html =
    "<html>\n" +
    "<body>\n"+
    "  <p>Hello World!</p>\n"+
    "</body>\n"+
    "</html>\n";

5. Use `.of()` instead of `.add()` when to init a list

✅ Use List.of()

var list = List.of(1, 2, 3);

🙅 Instead of Stream

var list = Collections.unmodifiableList(Stream.of(1, 2, 3).collect(toList()));

🙅 And instead of new ArrayList<>() and .add()

List<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(3);
list = Collections.unmodifiableList(list);

Conclusion

I've listed the 5 modern Java features I use most often. And using them gives me the joy of Java programming. 🍹

The official names of these features are:

By the way, the examples above are based on JDK 21, the latest LTS version.

What are your favorite modern Java features?

Sending both File and JSON in One Request to Spring Boot

Sean Evans — Wed, 18 Dec 2024 08:27:45 +0000

There are many people who use Spring Boot's @RequestPart to define an endpoint that receives both files and JSON data.

However, some of them encounter difficulties with how to test such endpoints, which is why I am writing this article.

⌨️ Parameters with `@RequestPart`

Typically, this type of endpoint is shown in the following code:

@RestController
@RequestMapping("/form-data")
public class FormDataController {
    @RequestMapping(value = "/json-and-file", method = POST)
    String jsonAndFile(@RequestPart User user,
                       @RequestPart MultipartFile file) {
       return "ok";
    }
}

I like to use modern Java, so I use records instead of Lombok or manually writing getters and setters. How about you?

public record User(String id, String name) {}

🤔 HTTP status code `415`

When using an HTTP Client such as Yaak, after submitting parameters via Multi-Part, I received a 415 status code. How frustrating.

At this point, open Spring Boot's console and you will see a warning that the content type "application/octet-stream" is not supported. The 415 status code means that the server does not support the media type of the current parameter.

Obviously, the user field is a JSON string, not a binary. Without setting the content type manually, the default value is wrong. Therefore, we just need to set the correct content type for the user field.

Don't worry, your backend code is correct.

😀 Solution: Set the `Content-Type` of the text field to `application/json`

Yaak is a very clean tool and I love it!

But it CAN'T help when faced with this complex scenario because it DOESN'T support set the content-type for text field of a multipart request. I tried Paw, Bruno and they DIDN'T work either.

Therefore, I have to use a professional tool that supports setting the content-type for each part, such as Apidog or Postman. BTW, I only found these two GUI tools can do.

[Updated on Dec 26, 2024] A week after I posted this article, Bruno released v1.37.0 to support this feature. Did they read this post?

After setting the user field's content-type to application/json, I successfully received the HTTP status code 200 responded by Spring Boot.

The problem is solved. 🎉

If you need a modern and professional API tool, try Apidog, which is a new versatile tool. Of course, Postman is also a good classic choice.

Would anyone use curl in this situation?

DEV Community: Sean Evans

Get Started with Modern Java Today: A Concise Guide

1. Use record instead of lombok

2. Use var instead of class name

3. Use STR."\{}" instead of + between strings

4. Use """ instead of "\n"+ between multiline strings

5. Use .of() instead of .add() when to init a list