Class annotation used to assist in the creation of toString()
methods in classes.
The @ToString
annotation instructs the compiler to execute an
AST transformation which adds the necessary toString() method.
It allows you to write classes in this shortened form:
@ToString
class Customer {
String first, last
int age
Date since = new Date()
Collection favItems
private answer = 42
}
println new Customer(first:'Tom', last:'Jones', age:21, favItems:['Books', 'Games'])
Which will have this output:
Customer(Tom, Jones, 21, Wed Jul 14 23:57:14 EST 2010, [Books, Games])There are numerous options to customize the format of the generated output. E.g. if you change the first annotation to:
@ToString(includeNames=true)
Then the output will be:
Customer(first:Tom, last:Jones, age:21, since:Wed Jul 14 23:57:50 EST 2010, favItems:[Books, Games])Or if you change the first annotation to:
@ToString(includeNames=true,includeFields=true,excludes="since,favItems")
Then the output will be:
Customer(first:Tom, last:Jones, age:21, answer:42)If you have this example:
import groovy.transform.ToString@ToString
class NamedThing { String name }@ToString
(includeNames=true,includeSuper=true) class AgedThing extends NamedThing { int age } String agedThingAsString = new AgedThing(name:'Lassie', age:5).toString() assert agedThingAsString == 'AgedThing(age:5, super:NamedThing(Lassie))'
@ToString
can also be used in conjunction with @Canonical
and @Immutable
.
If you want to omit fields or properties referring to null, you can use the ignoreNulls flag:
import groovy.transform.ToString
@ToString(ignoreNulls = true)
class NamedThing {
String name
}
assert new NamedThing(name: null).toString() == 'NamedThing()'
By default the fully-qualified class name is used as part of the generated toString. If you want to exclude the package, you can set the includePackage flag to false, e.g.:
package my.company
import groovy.transform.ToString
@ToString(includePackage = false)
class NamedThing {
String name
}
println new NamedThing(name: "Lassie")
Which results in:
NamedThing(name: Lassie)If the includePackage flag is
true
(the default), then the output will be:
my.company.NamedThing(name: Lassie)
More examples:
//--------------------------------------------------------------------------
// Most simple implementation of toString.
import groovy.transform.ToString
@ToString
class Person {
String name
List likes
private boolean active = false
}
def person = new Person(name: 'mrhaki', likes: ['Groovy', 'Java'])
assert person.toString() == 'Person(mrhaki, [Groovy, Java])'
//-------------------------------------------------------------------------- // includeNames to output the names of the properties. import groovy.transform.ToString @ToString(includeNames=true) class Person { String name List likes private boolean active = false } def person = new Person(name: 'mrhaki', likes: ['Groovy', 'Java']) assert person.toString() == 'Person(name:mrhaki, likes:[Groovy, Java])'
//-------------------------------------------------------------------------- // includeFields to not only output properties, but also field values. import groovy.transform.ToString @ToString(includeNames=true, includeFields=true) class Person { String name List likes private boolean active = false } def person = new Person(name: 'mrhaki', likes: ['Groovy', 'Java']) assert person.toString() == 'Person(name:mrhaki, likes:[Groovy, Java], active:false)'
//-------------------------------------------------------------------------- // Use includeSuper to include properties from super class in output. import groovy.transform.ToString @ToString(includeNames=true) class Person { String name List likes private boolean active = false } @ToString(includeSuper=true, includeNames=true) class Student extends Person { List courses } def student = new Student(name: 'mrhaki', likes: ['Groovy', 'Java'], courses: ['IT', 'Business']) assert student.toString() == 'Student(courses:[IT, Business], super:Person(name:mrhaki, likes:[Groovy, Java]))'
//-------------------------------------------------------------------------- // excludes active field and likes property from output import groovy.transform.ToString @ToString(includeNames=true, includeFields=true, excludes='active,likes') class Person { String name List likes private boolean active = false } def person = new Person(name: 'mrhaki', likes: ['Groovy', 'Java']) assert person.toString() == 'Person(name:mrhaki)'
//-------------------------------------------------------------------------- // Don't include the package name in the output package com.mrhaki.blog.groovy import groovy.transform.* @ToString(includePackage=false) class Course { String title Integer maxAttendees } final Course course = new Course(title: 'Groovy 101', maxAttendees: 200) assert course.toString() == 'Course(Groovy 101, 200)'
//-------------------------------------------------------------------------- // Don't use properties with null value. package com.mrhaki.blog.groovy import groovy.transform.* @ToString(ignoreNulls=true) class Course { String title Integer maxAttendees } final Course course = new Course(title: 'Groovy 101') assert course.toString() == 'com.mrhaki.blog.groovy.Course(Groovy 101)'
//-------------------------------------------------------------------------- // Cache toString() result. package com.mrhaki.blog.groovy import groovy.transform.* @ToString(cache=true) class Course { String title Integer maxAttendees } Course course = new Course(title: 'Groovy 101', maxAttendees: 200) assert course.toString() == 'com.mrhaki.blog.groovy.Course(Groovy 101, 200)' // Value change will not be reflected in toString(). course.title = 'Grails with REST' assert course.toString() == 'com.mrhaki.blog.groovy.Course(Groovy 101, 200)' assert course.title == 'Grails with REST'
Type | Name and Description |
---|---|
boolean |
cache Whether to cache toString() calculations. |
String[] |
excludes List of field and/or property names to exclude from generated toString. |
boolean |
ignoreNulls Don't display any fields or properties with value null. |
boolean |
includeFields Include fields as well as properties in the generated toString. |
boolean |
includeNames Whether to include names of properties/fields in the generated toString. |
boolean |
includePackage Whether to include the fully-qualified class name (i.e. including the package) or just the simple class name in the generated toString. |
boolean |
includeSuper Whether to include the toString() of super in the generated toString. |
boolean |
includeSuperProperties Whether to include super properties in the generated toString. |
String[] |
includes List of field and/or property names to include within the generated toString. |
Whether to cache toString() calculations. You should only set this to true if you know the object is immutable (or technically mutable but never changed). @default false
List of field and/or property names to exclude from generated toString. Must not be used if 'includes' is used. For convenience, a String with comma separated names can be used in addition to an array (using Groovy's literal list notation) of String values. @default {}
Don't display any fields or properties with value null. @default false
Include fields as well as properties in the generated toString. @default false
Whether to include names of properties/fields in the generated toString. @default false
Whether to include the fully-qualified class name (i.e. including the package) or just the simple class name in the generated toString. @default true
Whether to include the toString() of super in the generated toString. @default false
Whether to include super properties in the generated toString. @default false
List of field and/or property names to include within the generated toString. Must not be used if 'excludes' is used. For convenience, a String with comma separated names can be used in addition to an array (using Groovy's literal list notation) of String values. @default {}