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作者:riemann
blog.csdn.net/riemann_/article/details/105374987
一、@Getter and @Setter
使用@Getter
和/或@Setter
注释任何字段,以使lombok
自动生成默认的getter / setter
。
默认的getter
只是返回该字段,如果该字段被称为foo
,则名为getFoo
(如果该字段的类型为boolean
,则为isFoo
)。
默认生成的 getter / setter
方法是公共的,除非你明确指定一个AccessLevel
。合法访问级别为PUBLIC,PROTECTED,PACKAGE和PRIVATE
。
你还可以在类上添加@Getter
和/或@Setter
注释。在这种情况下,就好像你使用该注释来注释该类中的所有非静态字段一样。
你始终可以使用特殊的AccessLevel.NONE
访问级别来手动禁用任何字段的getter / setter
生成。这使你可以覆盖类上的@Getter,@Setter或@Data
注释的行为。
With Lombok:
import lombok.AccessLevel;
import lombok.Getter;
import lombok.Setter;
public class GetterSetterExample {
@Getter
@Setter
private int age = 10;
@Setter(AccessLevel.PROTECTED)
private String name;
@Override
public String toString() {
return String.format("%s (age: %d)", name, age);
}
}
Native Java:
public class GetterSetterExample {
private int age = 10;
private String name;
@Override
public String toString() {
return String.format("%s (age: %d)", name, age);
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
protected void setName(String name) {
this.name = name;
}
}
二、@ToString
任何类定义都可以使用@ToString
注释,以使lombok
生成toString()
方法的实现。
默认情况下,将打印所有非静态字段。如果要跳过某些字段,可以使用@ ToString.Exclude
注释这些字段。或者,可以通过使用@ToString(onlyExplicitlyIncluded = true)
,然后使用@ToString.Include
标记要包含的每个字段,来确切指定希望使用的字段。
通过将callSuper
设置为true
,可以将toString
的超类实现的输出包含到输出中。请注意,java.lang.Object中toString()
的默认实现几乎毫无意义。
With Lombok:
import lombok.ToString;
@ToString
public class ToStringExample {
private static final int STATIC_VAR = 10;
private String name;
private Shape shape = new Square(5, 10);
private String[] tags;
@ToString.Exclude
private int id;
public String getName() {
return this.name;
}
@ToString(callSuper=true, includeFieldNames=true)
public static class Square extends Shape {
private final int width, height;
public Square(int width, int height) {
this.width = width;
this.height = height;
}
}
}
Native Java:
import java.util.Arrays;
public class ToStringExample {
private static final int STATIC_VAR = 10;
private String name;
private Shape shape = new Square(5, 10);
private String[] tags;
private int id;
public String getName() {
return this.name;
}
public static class Square extends Shape {
private final int width, height;
public Square(int width, int height) {
this.width = width;
this.height = height;
}
@Override
public String toString() {
return "Square(super=" + super.toString() + ", width=" + this.width + ", height=" + this.height + ")";
}
}
@Override
public String toString() {
return "ToStringExample(" + this.getName() + ", " + this.shape + ", " + Arrays.deepToString(this.tags) + ")";
}
}
三、@EqualsAndHashCode
任何类定义都可以使用@EqualsAndHashCode
进行注释,以使lombok
生成equals(Object other)
和hashCode()
方法的实现。默认情况下,它将使用所有非静态,非瞬态字段,但是您可以通过使用@EqualsAndHashCode.Include
标记类型成员来修改使用哪些字段(甚至指定要使用各种方法的输出)。 @EqualsAndHashCode.Exclude
。或者,可以通过使用@ EqualsAndHashCode.Include
标记并使用@EqualsAndHashCode(onlyExplicitlyIncluded = true)
来精确指定要使用的字段或方法。
如果将@EqualsAndHashCode
应用于扩展另一个类的类,则此功能会有些棘手。通常,为此类自动生成equals
和hashCode
方法是一个坏主意,因为超类还定义了字段,该字段也需要equals / hashCode
代码,但不会生成此代码。通过将callSuper
设置为true
,可以在生成的方法中包括超类的equals
和hashCode
方法。
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With Lombok:
import lombok.EqualsAndHashCode;
@EqualsAndHashCode
public class EqualsAndHashCodeExample {
private transient int transientVar = 10;
private String name;
private double score;
@EqualsAndHashCode.Exclude
private Shape shape = new Square(5, 10);
private String[] tags;
@EqualsAndHashCode.Exclude
private int id;
public String getName() {
return this.name;
}
@EqualsAndHashCode(callSuper=true)
public static class Square extends Shape {
private final int width, height;
public Square(int width, int height) {
this.width = width;
this.height = height;
}
}
}
Native Java:
import java.util.Arrays;
public class EqualsAndHashCodeExample {
private transient int transientVar = 10;
private String name;
private double score;
private Shape shape = new Square(5, 10);
private String[] tags;
private int id;
public String getName() {
return this.name;
}
@Override
public boolean equals(Object o) {
if (o == this) return true;
if (!(o instanceof EqualsAndHashCodeExample)) return false;
EqualsAndHashCodeExample other = (EqualsAndHashCodeExample) o;
if (!other.canEqual((Object)this)) return false;
if (this.getName() == null ? other.getName() != null : !this.getName().equals(other.getName())) return false;
if (Double.compare(this.score, other.score) != 0) return false;
if (!Arrays.deepEquals(this.tags, other.tags)) return false;
return true;
}
@Override
public int hashCode() {
final int PRIME = 59;
int result = 1;
final long temp1 = Double.doubleToLongBits(this.score);
result = (result*PRIME) + (this.name == null ? 43 : this.name.hashCode());
result = (result*PRIME) + (int)(temp1 ^ (temp1 >>> 32));
result = (result*PRIME) + Arrays.deepHashCode(this.tags);
return result;
}
protected boolean canEqual(Object other) {
return other instanceof EqualsAndHashCodeExample;
}
public static class Square extends Shape {
private final int width, height;
public Square(int width, int height) {
this.width = width;
this.height = height;
}
@Override
public boolean equals(Object o) {
if (o == this) return true;
if (!(o instanceof Square)) return false;
Square other = (Square) o;
if (!other.canEqual((Object)this)) return false;
if (!super.equals(o)) return false;
if (this.width != other.width) return false;
if (this.height != other.height) return false;
return true;
}
@Override
public int hashCode() {
final int PRIME = 59;
int result = 1;
result = (result*PRIME) + super.hashCode();
result = (result*PRIME) + this.width;
result = (result*PRIME) + this.height;
return result;
}
protected boolean canEqual(Object other) {
return other instanceof Square;
}
}
}
四、@AllArgsConstructor, @RequiredArgsConstructor and @NoArgsConstructor
@NoArgsConstructor
将生成没有参数的构造函数。如果字段由final修饰,则将导致编译器错误,除非使用@NoArgsConstructor(force = true)
,否则所有final字段都将初始化为0 / false / null
。对于具有约束的字段(例如@NonNull
字段),不会生成任何检查。
@RequiredArgsConstructor
为每个需要特殊处理的字段生成一个带有1个参数的构造函数。所有未初始化的final字段都会获取一个参数,以及所有未声明其位置的未标记为@NonNull
的字段。
@AllArgsConstructor
为类中的每个字段生成一个带有1个参数的构造函数。标有@NonNull
的字段将对这些参数进行空检查。
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With Lombok:
import lombok.AccessLevel;
import lombok.RequiredArgsConstructor;
import lombok.AllArgsConstructor;
import lombok.NonNull;
@RequiredArgsConstructor(staticName = "of")
@AllArgsConstructor(access = AccessLevel.PROTECTED)
public class ConstructorExample<T> {
private int x, y;
@NonNull
private T description;
@NoArgsConstructor
public static class NoArgsExample {
@NonNull
private String field;
}
}
Native Java:
public class ConstructorExample<T> {
private int x, y;
@NonNull
private T description;
private ConstructorExample(T description) {
if (description == null) throw new NullPointerException("description");
this.description = description;
}
public static <T> ConstructorExample<T> of(T description) {
return new ConstructorExample<T>(description);
}
@java.beans.ConstructorProperties({"x", "y", "description"})
protected ConstructorExample(int x, int y, T description) {
if (description == null) throw new NullPointerException("description");
this.x = x;
this.y = y;
this.description = description;
}
public static class NoArgsExample {
@NonNull
private String field;
public NoArgsExample() {
}
}
}
五、@Data
@Data
是一个方便的快捷方式批注,它将@ToString
,@EqualsAndHashCode
,@ Getter / @Setter
和@RequiredArgsConstructor
的功能捆绑在一起:换句话说,@Data
生成通常与简单POJO
关联的所有样板(普通的旧Java
对象)和bean
:所有字段的getter
,所有非final
字段的setter
,以及涉及类字段的适当的toString
,equals
和hashCode
实现,以及初始化所有final
字段以及所有非final
字段的构造函数没有使用@NonNull
标记的初始化程序,以确保该字段永远不会为null
。
With Lombok:
import lombok.AccessLevel;
import lombok.Setter;
import lombok.Data;
import lombok.ToString;
@Data
public class DataExample {
private final String name;
@Setter(AccessLevel.PACKAGE)
private int age;
private double score;
private String[] tags;
@ToString(includeFieldNames=true)
@Data(staticConstructor="of")
public static class Exercise<T> {
private final String name;
private final T value;
}
}
Native Java:
import java.util.Arrays;
public class DataExample {
private final String name;
private int age;
private double score;
private String[] tags;
public DataExample(String name) {
this.name = name;
}
public String getName() {
return this.name;
}
void setAge(int age) {
this.age = age;
}
public int getAge() {
return this.age;
}
public void setScore(double score) {
this.score = score;
}
public double getScore() {
return this.score;
}
public String[] getTags() {
return this.tags;
}
public void setTags(String[] tags) {
this.tags = tags;
}
@Override
public String toString() {
return "DataExample(" + this.getName() + ", " + this.getAge() + ", " + this.getScore() + ", " + Arrays.deepToString(this.getTags()) + ")";
}
protected boolean canEqual(Object other) {
return other instanceof DataExample;
}
@Override
public boolean equals(Object o) {
if (o == this) return true;
if (!(o instanceof DataExample)) return false;
DataExample other = (DataExample) o;
if (!other.canEqual((Object)this)) return false;
if (this.getName() == null ? other.getName() != null : !this.getName().equals(other.getName())) return false;
if (this.getAge() != other.getAge()) return false;
if (Double.compare(this.getScore(), other.getScore()) != 0) return false;
if (!Arrays.deepEquals(this.getTags(), other.getTags())) return false;
return true;
}
@Override
public int hashCode() {
final int PRIME = 59;
int result = 1;
final long temp1 = Double.doubleToLongBits(this.getScore());
result = (result*PRIME) + (this.getName() == null ? 43 : this.getName().hashCode());
result = (result*PRIME) + this.getAge();
result = (result*PRIME) + (int)(temp1 ^ (temp1 >>> 32));
result = (result*PRIME) + Arrays.deepHashCode(this.getTags());
return result;
}
public static class Exercise<T> {
private final String name;
private final T value;
private Exercise(String name, T value) {
this.name = name;
this.value = value;
}
public static <T> Exercise<T> of(String name, T value) {
return new Exercise<T>(name, value);
}
public String getName() {
return this.name;
}
public T getValue() {
return this.value;
}
@Override
public String toString() {
return "Exercise(name=" + this.getName() + ", value=" + this.getValue() + ")";
}
protected boolean canEqual(Object other) {
return other instanceof Exercise;
}
@Override
public boolean equals(Object o) {
if (o == this) return true;
if (!(o instanceof Exercise)) return false;
Exercise<?> other = (Exercise<?>) o;
if (!other.canEqual((Object)this)) return false;
if (this.getName() == null ? other.getValue() != null : !this.getName().equals(other.getName())) return false;
if (this.getValue() == null ? other.getValue() != null : !this.getValue().equals(other.getValue())) return false;
return true;
}
@Override
public int hashCode() {
final int PRIME = 59;
int result = 1;
result = (result*PRIME) + (this.getName() == null ? 43 : this.getName().hashCode());
result = (result*PRIME) + (this.getValue() == null ? 43 : this.getValue().hashCode());
return result;
}
}
}
六、@Value
@Value注解和@Data
类似,区别在于它会把所有成员变量默认定义为private final
修饰,并且不会生成set
方法。
七、@Builder
构建者模式
只能标注到类上,将生成类的一个当前流程的一种链式构造工厂,如下:
User buildUser = User.builder().username("riemann").password("123").build();
可配合@Singular
注解使用,@Singular
注解使用在jdk内部集合类型的属性,Map
类型的属性以及Guava
的com.google.common.collect
的属性上。例如 未标注@Singular
的属性,一般setter
时,会直接覆盖原来的引用,标注了@Singular
的属性,集合属性支持添加操作,会在属性原来的基础上增加。
With Lombok:
import lombok.Builder;
import lombok.Singular;
import java.util.Set;
@Builder
public class BuilderExample {
@Builder.Default
private long created = System.currentTimeMillis();
private String name;
private int age;
@Singular
private Set<String> occupations;
}
Native Java:
import java.util.Set;
public class BuilderExample {
private long created;
private String name;
private int age;
private Set<String> occupations;
BuilderExample(String name, int age, Set<String> occupations) {
this.name = name;
this.age = age;
this.occupations = occupations;
}
private static long $default$created() {
return System.currentTimeMillis();
}
public static BuilderExampleBuilder builder() {
return new BuilderExampleBuilder();
}
public static class BuilderExampleBuilder {
private long created;
private boolean created$set;
private String name;
private int age;
private java.util.ArrayList<String> occupations;
BuilderExampleBuilder() {
}
public BuilderExampleBuilder created(long created) {
this.created = created;
this.created$set = true;
return this;
}
public BuilderExampleBuilder name(String name) {
this.name = name;
return this;
}
public BuilderExampleBuilder age(int age) {
this.age = age;
return this;
}
public BuilderExampleBuilder occupation(String occupation) {
if (this.occupations == null) {
this.occupations = new java.util.ArrayList<String>();
}
this.occupations.add(occupation);
return this;
}
public BuilderExampleBuilder occupations(Collection<? extends String> occupations) {
if (this.occupations == null) {
this.occupations = new java.util.ArrayList<String>();
}
this.occupations.addAll(occupations);
return this;
}
public BuilderExampleBuilder clearOccupations() {
if (this.occupations != null) {
this.occupations.clear();
}
return this;
}
public BuilderExample build() {
// complicated switch statement to produce a compact properly sized immutable set omitted.
Set<String> occupations = ...;
return new BuilderExample(created$set ? created : BuilderExample.$default$created(), name, age, occupations);
}
@java.lang.Override
public String toString() {
return "BuilderExample.BuilderExampleBuilder(created = " + this.created + ", name = " + this.name + ", age = " + this.age + ", occupations = " + this.occupations + ")";
}
}
}
八、@Accessors
链式风格
@Accessors
批注用于配置lombok
如何生成和查找getter
和setter
。
默认情况下,lombok
遵循针对getter
和setter
的bean
规范:例如,名为Pepper
的字段的getter
是getPepper
。但是,有些人可能希望打破bean
规范,以得到更好看的API
。 @Accessors
允许您执行此操作。
可标注在类或属性上,当然最实用的功能还是标注到类上。
标注到类上,chain
属性设置为true
时,类的所有属性的setter
方法返回值将为this
,用来支持setter
方法的链式写法。如:
new User().setUsername("riemann").setPassword("123");
fluent
属性设置为true
时,类的所有getter
,setter
方法将省略get
和set
前缀,获取属性值直接使用属性名相同的无参方法,设置属性值使用属性名相同的有参方法,并且返回值为this。如:
User user = new User().username("riemann").password("123");
String username = user.username();
String password = user.password();
标注到属性上,使用prefix
设置需要省略的属性生成getter
,setter
方法时的前缀,且属性必须为驼峰式命名。
@Accessors(prefix = "r")
@Getter
@Setter
private String rUsername = "riemann";
编译之后为
public String getUsername() {
return rUsername;
}
public void setUsername(String rUsername) {
this.rUsername = rUsername;
}
九、@Slf4j and @Log4j
在需要打印日志的类中使用,项目中使用slf4j
、log4j
日志框架
十、@NonNull
该注解快速判断是否为空,为空抛出java.lang.NullPointerException
。
十一、@Synchronized
注解自动添加到同步机制,生成的代码并不是直接锁方法,而是锁代码块, 作用范围是方法上。
十二、@Cleanup
注解用于确保已分配的资源被释放(IO
的连接关闭)。
原文始发于微信公众号(全栈程序员社区):超级全面的 Lombok 注解介绍,学一波!
发布者:全栈程序员-用户IM,转载请注明出处:https://javaforall.cn/102404.html原文链接:https://javaforall.cn
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