@Documented @Retention(RUNTIME) @Target(TYPE) public @interface ToString

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'

Since:

1.8.0

See Also:

Immutable
Canonical

Optional Element Summary

Optional Elements

Modifier and Type

Optional Element

Description

boolean

allNames

Whether to include all fields and/or properties in the generated toString, including those with names that are considered internal.

boolean

allProperties

Whether to include all properties (as per the JavaBean spec) in the generated toString.

boolean

cache

Whether to cache toString() calculations.

String[]

excludes

List of field and/or property names to exclude from generated toString.

String

fieldSeparator

The string to use between each property/field.

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.

String[]

includes

List of field and/or property names to include within the generated toString.

boolean

includeSuper

Whether to include the toString() of super in the generated toString.

boolean

includeSuperFields

Include super fields in the generated toString.

boolean

includeSuperProperties

Whether to include super properties in the generated toString.

String

leftDelimiter

The String to use after the classname and before the list of properties/fields.

String

nameValueSeparator

The string to use between the name of the property/field and its value when includeNames is true.

boolean

pojo

Whether to avoid using Groovy runtime methods when printing the toString for class members.

String

rightDelimiter

The String to use after the list of properties/fields.

boolean

useGetters

Whether to access properties directly by their fields (faster) or via their getters.

Element Details
- excludes
  
  String[] excludes
  
  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:
  
  {}
- includes
  
  String[] includes
  
  List of field and/or property names to include within the generated toString. The order of inclusion is determined by the order in which the names are specified. 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. The default value is a special marker value indicating that no includes are defined; all fields and/or properties are included if 'includes' remains undefined and 'excludes' is explicitly or implicitly an empty list. The special name 'super' can be used instead of using the 'includeSuper' flag.
  
  Default:
  
  {"<DummyUndefinedMarkerString-DoNotUse>"}
- includeSuper
  
  boolean includeSuper
  
  Whether to include the toString() of super in the generated toString.
  
  Default:
  
  false
- includeNames
  
  boolean includeNames
  
  Whether to include names of properties/fields in the generated toString.
  
  Default:
  
  false
- includeFields
  
  boolean includeFields
  
  Include fields as well as properties in the generated toString. Fields come after any properties.
  
  Default:
  
  false
- includeSuperProperties
  
  boolean includeSuperProperties
  
  Whether to include super properties in the generated toString. Groovy properties, JavaBean properties and fields (in that order) from superclasses come after the members from a subclass (unless 'includes' is used to determine the order).
  
  Since:
  
  2.4.0
  
  Default:
  
  false
- includeSuperFields
  
  boolean includeSuperFields
  
  Include super fields in the generated toString. Groovy properties, JavaBean properties and fields (in that order) from superclasses come after the members from a subclass (unless 'includes' is used to determine the order).
  
  Since:
  
  2.5.0
  
  Default:
  
  false
- ignoreNulls
  
  boolean ignoreNulls
  
  Don't display any fields or properties with value null.
  
  Default:
  
  false
- includePackage
  
  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.
  
  Since:
  
  2.0.6
  
  Default:
  
  true
- allProperties
  
  boolean allProperties
  
  Whether to include all properties (as per the JavaBean spec) in the generated toString. Groovy recognizes any field-like definitions with no explicit visibility as property definitions and always includes them in the @ToString generated toString (as well as auto-generating the appropriate getters and setters). Groovy also treats any explicitly created getXxx() or isYyy() methods as property getters as per the JavaBean specification. Old versions of Groovy did not. So set this flag to false for the old behavior or if you want to explicitly exclude such properties. JavaBean properties come after any Groovy properties but before any fields for a given class (unless 'includes' is used to determine the order).
  
  Since:
  
  2.5.0
  
  Default:
  
  true
- cache
  
  boolean cache
  
  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).
  
  Since:
  
  2.1.0
  
  Default:
  
  false
- allNames
  
  boolean allNames
  
  Whether to include all fields and/or properties in the generated toString, including those with names that are considered internal.
  
  Since:
  
  2.5.0
  
  Default:
  
  false
- pojo
  
  boolean pojo
  
  Whether to avoid using Groovy runtime methods when printing the toString for class members. The generated code is more similar to what is typically used in POJO classes. The presence of the @POJO annotation on a class is looked for by default but this annotation attribute allows the feature to be explicitly configured if desired. NOTE: this is an incubating feature and may change in future versions.
  
  Since:
  
  4.0.0
  
  Default:
  
  false
- leftDelimiter
  
  String leftDelimiter
  
  The String to use after the classname and before the list of properties/fields.
  
  Since:
  
  4.0.0
  
  Default:
  
  "("
- rightDelimiter
  
  String rightDelimiter
  
  The String to use after the list of properties/fields.
  
  Since:
  
  4.0.0
  
  Default:
  
  ")"
- nameValueSeparator
  
  String nameValueSeparator
  
  The string to use between the name of the property/field and its value when includeNames is true.
  
  Since:
  
  4.0.0
  
  Default:
  
  ":"
- fieldSeparator
  
  String fieldSeparator
  
  The string to use between each property/field.
  
  Since:
  
  4.0.0
  
  Default:
  
  ", "
- useGetters
  
  boolean useGetters
  
  Whether to access properties directly by their fields (faster) or via their getters.
  
  Since:
  
  4.0.12
  
  Default:
  
  true

Annotation Type ToString

Optional Element Summary

Element Details

excludes

includes

includeSuper

includeNames

includeFields

includeSuperProperties

includeSuperFields

ignoreNulls

includePackage

allProperties

cache

allNames

pojo

leftDelimiter

rightDelimiter

nameValueSeparator

fieldSeparator

useGetters