/*
* Copyright (C) 2013-2018 The Project Lombok Authors.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package lombok;
import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
The builder annotation creates a so-called 'builder' aspect to the class that is annotated or the class that contains a member which is annotated with @Builder. If a member is annotated, it must be either a constructor or a method. If a class is annotated, then a private constructor is generated with all fields as arguments (as if @AllArgsConstructor(access = AccessLevel.PRIVATE) is present on the class), and it is as if this constructor has been annotated with @Builder instead. Note that this constructor is only generated if you haven't written any constructors and also haven't added any explicit @XArgsConstructor annotations. In those cases, lombok will assume an all-args constructor is present and generate code that uses it; this means you'd get a compiler error if this constructor is not present.
The effect of @Builder is that an inner class is generated named TBuilder,
with a private constructor. Instances of TBuilder are made with the method named builder() which is also generated for you in the class itself (not in the builder class).
The TBuilder class contains 1 method for each parameter of the annotated
constructor / method (each field, when annotating a class), which returns the builder itself.
The builder also has a build() method which returns a completed instance of the original type, created by passing all parameters as set via the various other methods in the builder to the constructor or method that was annotated with @Builder. The return type of this method will be the same as the relevant class, unless a method has been annotated, in which case it'll be equal to the return type of that method.
Complete documentation is found at the project lombok features page for @Builder.
Before:
@Builder
class Example<T> {
private T foo;
private final String bar;
}
After:
class Example<T> {
private T foo;
private final String bar;
private Example(T foo, String bar) {
this.foo = foo;
this.bar = bar;
}
public static <T> ExampleBuilder<T> builder() {
return new ExampleBuilder<T>();
}
public static class ExampleBuilder<T> {
private T foo;
private String bar;
private ExampleBuilder() {}
public ExampleBuilder foo(T foo) {
this.foo = foo;
return this;
}
public ExampleBuilder bar(String bar) {
this.bar = bar;
return this;
}
@java.lang.Override public String toString() {
return "ExampleBuilder(foo = " + foo + ", bar = " + bar + ")";
}
public Example build() {
return new Example(foo, bar);
}
}
}
See Also:
/**
* The builder annotation creates a so-called 'builder' aspect to the class that is annotated or the class
* that contains a member which is annotated with {@code @Builder}.
* <p>
* If a member is annotated, it must be either a constructor or a method. If a class is annotated,
* then a private constructor is generated with all fields as arguments
* (as if {@code @AllArgsConstructor(access = AccessLevel.PRIVATE)} is present
* on the class), and it is as if this constructor has been annotated with {@code @Builder} instead.
* Note that this constructor is only generated if you haven't written any constructors and also haven't
* added any explicit {@code @XArgsConstructor} annotations. In those cases, lombok will assume an all-args
* constructor is present and generate code that uses it; this means you'd get a compiler error if this
* constructor is not present.
* <p>
* The effect of {@code @Builder} is that an inner class is generated named <code><strong>T</strong>Builder</code>,
* with a private constructor. Instances of <code><strong>T</strong>Builder</code> are made with the
* method named {@code builder()} which is also generated for you in the class itself (not in the builder class).
* <p>
* The <code><strong>T</strong>Builder</code> class contains 1 method for each parameter of the annotated
* constructor / method (each field, when annotating a class), which returns the builder itself.
* The builder also has a <code>build()</code> method which returns a completed instance of the original type,
* created by passing all parameters as set via the various other methods in the builder to the constructor
* or method that was annotated with {@code @Builder}. The return type of this method will be the same
* as the relevant class, unless a method has been annotated, in which case it'll be equal to the
* return type of that method.
* <p>
* Complete documentation is found at <a href="https://projectlombok.org/features/Builder">the project lombok features page for @Builder</a>.
* <br>
* <p>
* Before:
*
* <pre>
* @Builder
* class Example<T> {
* private T foo;
* private final String bar;
* }
* </pre>
*
* After:
*
* <pre>
* class Example<T> {
* private T foo;
* private final String bar;
*
* private Example(T foo, String bar) {
* this.foo = foo;
* this.bar = bar;
* }
*
* public static <T> ExampleBuilder<T> builder() {
* return new ExampleBuilder<T>();
* }
*
* public static class ExampleBuilder<T> {
* private T foo;
* private String bar;
*
* private ExampleBuilder() {}
*
* public ExampleBuilder foo(T foo) {
* this.foo = foo;
* return this;
* }
*
* public ExampleBuilder bar(String bar) {
* this.bar = bar;
* return this;
* }
*
* @java.lang.Override public String toString() {
* return "ExampleBuilder(foo = " + foo + ", bar = " + bar + ")";
* }
*
* public Example build() {
* return new Example(foo, bar);
* }
* }
* }
* </pre>
*
* @see Singular
*/
@Target({TYPE, METHOD, CONSTRUCTOR})
@Retention(SOURCE)
public @interface Builder {
The field annotated with @Default must have an initializing expression; that expression is taken as the default to be used if not explicitly set during building. /**
* The field annotated with {@code @Default} must have an initializing expression; that expression is taken as the default to be used if not explicitly set during building.
*/
@Target(FIELD)
@Retention(SOURCE)
public @interface Default {}
Returns: Name of the method that creates a new builder instance. Default: builder.
/** @return Name of the method that creates a new builder instance. Default: {@code builder}. */
String builderMethodName() default "builder";
Returns: Name of the method in the builder class that creates an instance of your @Builder-annotated class.
/** @return Name of the method in the builder class that creates an instance of your {@code @Builder}-annotated class. */
String buildMethodName() default "build";
Name of the builder class. Default for @Builder on types and constructors: (TypeName)Builder. Default for @Builder on methods: (ReturnTypeName)Builder.
Returns: Name of the builder class that will be generated (or if it already exists, will be filled with builder elements).
/**
* Name of the builder class.
*
* Default for {@code @Builder} on types and constructors: {@code (TypeName)Builder}.
* <p>
* Default for {@code @Builder} on methods: {@code (ReturnTypeName)Builder}.
*
* @return Name of the builder class that will be generated (or if it already exists, will be filled with builder elements).
*/
String builderClassName() default "";
If true, generate an instance method to obtain a builder that is initialized with the values of this instance. Legal only if @Builder is used on a constructor, on the type itself, or on a static method that returns an instance of the declaring type. Returns: Whether to generate a toBuilder() method.
/**
* If true, generate an instance method to obtain a builder that is initialized with the values of this instance.
* Legal only if {@code @Builder} is used on a constructor, on the type itself, or on a static method that returns
* an instance of the declaring type.
*
* @return Whether to generate a {@code toBuilder()} method.
*/
boolean toBuilder() default false;
Put on a field (in case of @Builder on a type) or a parameter (for @Builder on a constructor or static method) to indicate how lombok should obtain a value for this field or parameter given an instance; this is only relevant if toBuilder is true. You do not need to supply an @ObtainVia annotation unless you wish to change the default behaviour: Use a field with the same name. Note that one of field or method should be set, or an error is generated.
The default behaviour is to obtain a value by referencing the name of the parameter as a field on 'this'.
/**
* Put on a field (in case of {@code @Builder} on a type) or a parameter (for {@code @Builder} on a constructor or static method) to
* indicate how lombok should obtain a value for this field or parameter given an instance; this is only relevant if {@code toBuilder} is {@code true}.
*
* You do not need to supply an {@code @ObtainVia} annotation unless you wish to change the default behaviour: Use a field with the same name.
* <p>
* Note that one of {@code field} or {@code method} should be set, or an error is generated.
* <p>
* The default behaviour is to obtain a value by referencing the name of the parameter as a field on 'this'.
*/
@Target({FIELD, PARAMETER})
@Retention(SOURCE)
public @interface ObtainVia {
Returns: Tells lombok to obtain a value with the expression this.value.
/**
* @return Tells lombok to obtain a value with the expression {@code this.value}.
*/
String field() default "";
Returns: Tells lombok to obtain a value with the expression this.method().
/**
* @return Tells lombok to obtain a value with the expression {@code this.method()}.
*/
String method() default "";
Returns: Tells lombok to obtain a value with the expression SelfType.method(this); requires method to be set.
/**
* @return Tells lombok to obtain a value with the expression {@code SelfType.method(this)}; requires {@code method} to be set.
*/
boolean isStatic() default false;
}
}