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How to change name of fields with @ToString annotation in Lombok

abhilash

Overview

The @ToString annotation is one of the annotations in the project Lombok.

Note: Refer What is the @ToString annotation in Lombok? for the introduction of the annotation.

The @ToString annotation generates an implementation for the toString() method where the class name, along with each field in order, separated by commas, is printed. But sometimes, the names of the fields need to be different in the string representation of the fields.

For example, consider a Person class with three attributes, name, age, and address:

@ToString
@AllArgsConstructor
class Person {
      private int age;
      private String name;
      private String address;
}

We define an instance of the Person class:

Person person = new Person(30, "sam", "US");

The default string representation of the above object is as follows:

Person(age=30, name=sam, address=US)

The names of the fields are as defined in the class. If we want to change the names of the fields while printing, we do as follows:

Person(Username=sam, Country=US, Age=30)

name parameter

The name parameter of the Include interface of the ToString annotation is used to give a different name to fields in the string representation.

Code

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>test</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
            <scope>provided</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>2.1</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>Main</mainClass>
                                </transformer>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

Explanation

  • Lines 1 and 2: We import the AllArgsConstructor and ToString annotations.

  • Lines 6 to 8: We define the Person class annotated with @AllArgsConstructor and @ToString annotations.

  • Lines 10 and 11: We define the age field with Age.

  • Lines 13 and 14: We define the name field with Username.

  • Lines 16 and 17: We define the address field with Country.

  • Line 22: We create an instance of the Person class.

  • Line 23: We print the person instance created in line 22 to console.

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