Lombok 簡(jiǎn)介
Lombok項(xiàng)目通過(guò)添加“處理程序”，使java成為一種更為簡(jiǎn)單的語(yǔ)言。
簡(jiǎn)單來(lái)說(shuō)，比如我們新建了一個(gè)類泉褐，然后在其中寫(xiě)了幾個(gè)字段，然后通常情況下我們需要手動(dòng)去建立getter和setter方法啊鸟蜡，構(gòu)造函數(shù)啊之類的膜赃，Lombok的作用就是為了省去我們手動(dòng)創(chuàng)建這些代碼的麻煩，它能夠在我們編譯源碼的時(shí)候自動(dòng)幫我們生成這些方法揉忘。Lombok能夠達(dá)到的效果就是在源碼中不需要寫(xiě)一些通用的方法跳座，但是在編譯生成的字節(jié)碼文件中會(huì)幫我們生成這些方法，這就是Lombok的神奇作用泣矛。雖然有人可能會(huì)說(shuō)IDE里面都自帶自動(dòng)生成這些方法的功能疲眷，但是使用Lombok會(huì)使你的代碼看起來(lái)更加簡(jiǎn)潔，寫(xiě)起來(lái)也更加方便您朽。
IntelliJ IDEA安裝lombok插件
菜單欄File > Settings > Plugins > Browse repositories...
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搜索 Lombok Plugin 安裝后狂丝，重啟IDEA即可生效
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添加lombok依賴
<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.16</version>
</dependency>
Lombok使用
1.val
如果對(duì)其他的語(yǔ)言有研究的會(huì)發(fā)現(xiàn)，很多語(yǔ)言是使用var作為變量申明哗总，val作為常量申明几颜。這里的val也是這個(gè)作用。
public String example() {
val example = new ArrayList<String>();
example.add("Hello, World!");
val foo = example.get(0);
return foo.toLowerCase();
}
翻譯成Java程序是：
public String example() {
final ArrayList<String> example = new ArrayList<String>();
example.add("Hello, World!");
final String foo = example.get(0);
return foo.toLowerCase();
}
2.@NonNull
Null即是罪惡
public class NonNullExample extends Something {
private String name;
public NonNullExample(@NonNull Person person) {
super("Hello");
this.name = person.getName();
}
}
翻譯成 Java 程序是：
public class NonNullExample extends Something {
private String name;
public NonNullExample(@NonNull Person person) {
super("Hello");
if (person == null) {
throw new NullPointerException("person");
}
this.name = person.getName();
}
}
3.Cleanup
自動(dòng)化才是生產(chǎn)力
public class CleanupExample {
public static void main(String[] args) throws IOException {
@Cleanup InputStream in = new FileInputStream(args[0]);
@Cleanup OutputStream out = new FileOutputStream(args[1]);
byte[] b = new byte[10000];
while (true) {
int r = in.read(b);
if (r == -1) break;
out.write(b, 0, r);
}
}
}
翻譯成Java程序是：
public class CleanupExample {
public static void main(String[] args) throws IOException {
InputStream in = new FileInputStream(args[0]);
try {
OutputStream out = new FileOutputStream(args[1]);
try {
byte[] b = new byte[10000];
while (true) {
int r = in.read(b);
if (r == -1) break;
out.write(b, 0, r);
}
} finally {
if (out != null) {
out.close();
}
}
} finally {
if (in != null) {
in.close();
}
}
}
}
4.@Getter/@Setter
再也不寫(xiě) public int getFoo() {return foo;}
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);
}
}
翻譯成Java程序是：
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;
}
}
5.@ToString
Debug Log 最強(qiáng)幫手
@ToString(exclude="id")
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.getName();
}
@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;
}
}
}
翻譯成 Java 程序是：
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.getName();
}
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) + ")";
}
}
6. @NoArgsConstructor, @RequiredArgsConstructor and @AllArgsConstructor
@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;
}
}
翻譯成 Java 程序是：
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() {
}
}
}
7.@Data
這個(gè)就相當(dāng)?shù)暮?jiǎn)單啦讯屈，因?yàn)槲覀儼l(fā)現(xiàn) @ToString, @EqualsAndHashCode, @Getter 都很常用菠剩，這個(gè)一個(gè)注解就相當(dāng)于
@ToString, @EqualsAndHashCode, @Getter(所有字段), @Setter (所有非final字段), @RequiredArgsConstructor!
8. @Value
@Value 就是 @Data 的不可變版本
@Value public class ValueExample {
String name;
@Wither(AccessLevel.PACKAGE) @NonFinal int age;
double score;
protected String[] tags;
@ToString(includeFieldNames=true)
@Value(staticConstructor="of")
public static class Exercise<T> {
String name;
T value;
}
}
翻譯成 Java 程序是：
public final class ValueExample {
private final String name;
private int age;
private final double score;
protected final String[] tags;
@java.beans.ConstructorProperties({"name", "age", "score", "tags"})
public ValueExample(String name, int age, double score, String[] tags) {
this.name = name;
this.age = age;
this.score = score;
this.tags = tags;
}
public String getName() {
return this.name;
}
public int getAge() {
return this.age;
}
public double getScore() {
return this.score;
}
public String[] getTags() {
return this.tags;
}
@java.lang.Override
public boolean equals(Object o) {
if (o == this) return true;
if (!(o instanceof ValueExample)) return false;
final ValueExample other = (ValueExample)o;
final Object this$name = this.getName();
final Object other$name = other.getName();
if (this$name == null ? other$name != null : !this$name.equals(other$name)) 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;
}
@java.lang.Override
public int hashCode() {
final int PRIME = 59;
int result = 1;
final Object $name = this.getName();
result = result * PRIME + ($name == null ? 43 : $name.hashCode());
result = result * PRIME + this.getAge();
final long $score = Double.doubleToLongBits(this.getScore());
result = result * PRIME + (int)($score >>> 32 ^ $score);
result = result * PRIME + Arrays.deepHashCode(this.getTags());
return result;
}
@java.lang.Override
public String toString() {
return "ValueExample(name=" + getName() + ", age=" + getAge() + ", score=" + getScore() + ", tags=" + Arrays.deepToString(getTags()) + ")";
}
ValueExample withAge(int age) {
return this.age == age ? this : new ValueExample(name, age, score, tags);
}
public static final class Exercise<T> {
private final String name;
private final T value;
private Exercise(String name, T value) {
this.name = name;
this.value = value;
}
public static <T> Exercise<T> of(String name, T value) {
return new Exercise<T>(name, value);
}
public String getName() {
return this.name;
}
public T getValue() {
return this.value;
}
@java.lang.Override
public boolean equals(Object o) {
if (o == this) return true;
if (!(o instanceof ValueExample.Exercise)) return false;
final Exercise<?> other = (Exercise<?>)o;
final Object this$name = this.getName();
final Object other$name = other.getName();
if (this$name == null ? other$name != null : !this$name.equals(other$name)) return false;
final Object this$value = this.getValue();
final Object other$value = other.getValue();
if (this$value == null ? other$value != null : !this$value.equals(other$value)) return false;
return true;
}
@java.lang.Override
public int hashCode() {
final int PRIME = 59;
int result = 1;
final Object $name = this.getName();
result = result * PRIME + ($name == null ? 43 : $name.hashCode());
final Object $value = this.getValue();
result = result * PRIME + ($value == null ? 43 : $value.hashCode());
return result;
}
@java.lang.Override
public String toString() {
return "ValueExample.Exercise(name=" + getName() + ", value=" + getValue() + ")";
}
}
}
9. @Builder
builder是現(xiàn)在比較推崇的一種構(gòu)建值對(duì)象的方式
@Builder
public class BuilderExample {
private String name;
private int age;
@Singular private Set<String> occupations;
}
翻譯成 Java 程序是：
public class BuilderExample {
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;
}
public static BuilderExampleBuilder builder() {
return new BuilderExampleBuilder();
}
public static class BuilderExampleBuilder {
private String name;
private int age;
private java.util.ArrayList<String> occupations;
BuilderExampleBuilder() {
}
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.
// go to https://projectlombok.org/features/Singular-snippet.html to see it.
Set<String> occupations = ...;
return new BuilderExample(name, age, occupations);
}
@java.lang.Override
public String toString() {
return "BuilderExample.BuilderExampleBuilder(name = " + this.name + ", age = " + this.age + ", occupations = " + this.occupations + ")";
}
}
}
10. @SneakyThrows
To RuntimeException 小助手
public class SneakyThrowsExample implements Runnable {
@SneakyThrows(UnsupportedEncodingException.class)
public String utf8ToString(byte[] bytes) {
return new String(bytes, "UTF-8");
}
@SneakyThrows
public void run() {
throw new Throwable();
}
}
翻譯成 Java 程序是：
public class SneakyThrowsExample implements Runnable {
public String utf8ToString(byte[] bytes) {
try {
return new String(bytes, "UTF-8");
} catch (UnsupportedEncodingException e) {
throw Lombok.sneakyThrow(e);
}
}
public void run() {
try {
throw new Throwable();
} catch (Throwable t) {
throw Lombok.sneakyThrow(t);
}
}
}
很好的隱藏了異常，有時(shí)候的確會(huì)有這樣的煩惱耻煤，從某種程度上也是遵循的了 let is crash
11. @Synchronized
public class SynchronizedExample {
private final Object readLock = new Object();
@Synchronized
public static void hello() {
System.out.println("world");
}
@Synchronized
public int answerToLife() {
return 42;
}
@Synchronized("readLock")
public void foo() {
System.out.println("bar");
}
}
翻譯成 Java 程序是：
public class SynchronizedExample {
private static final Object $LOCK = new Object[0];
private final Object $lock = new Object[0];
private final Object readLock = new Object();
public static void hello() {
synchronized($LOCK) {
System.out.println("world");
}
}
public int answerToLife() {
synchronized($lock) {
return 42;
}
}
public void foo() {
synchronized(readLock) {
System.out.println("bar");
}
}
}
這個(gè)就比較簡(jiǎn)單直接添加了synchronized關(guān)鍵字就Ok啦。不過(guò)現(xiàn)在JDK也比較推薦的是 Lock 對(duì)象准颓，這個(gè)可能用的不是特別多哈蝇。
12. @Getter(lazy=true)
節(jié)約是美德
public class GetterLazyExample {
@Getter(lazy=true) private final double[] cached = expensive();
private double[] expensive() {
double[] result = new double[1000000];
for (int i = 0; i < result.length; i++) {
result[i] = Math.asin(i);
}
return result;
}
}
翻譯成 Java 程序是：
public class GetterLazyExample {
private final java.util.concurrent.AtomicReference<java.lang.Object> cached = new java.util.concurrent.AtomicReference<java.lang.Object>();
public double[] getCached() {
java.lang.Object value = this.cached.get();
if (value == null) {
synchronized(this.cached) {
value = this.cached.get();
if (value == null) {
final double[] actualValue = expensive();
value = actualValue == null ? this.cached : actualValue;
this.cached.set(value);
}
}
}
return (double[])(value == this.cached ? null : value);
}
private double[] expensive() {
double[] result = new double[1000000];
for (int i = 0; i < result.length; i++) {
result[i] = Math.asin(i);
}
return result;
}
}
13. @Log
再也不用寫(xiě)那些差不多的Log啦
@Log
public class LogExample {
public static void main(String... args) {
log.error("Something's wrong here");
}
}
@Slf4j
public class LogExampleOther {
public static void main(String... args) {
log.error("Something else is wrong here");
}
}
@CommonsLog(topic="CounterLog")
public class LogExampleCategory {
public static void main(String... args) {
log.error("Calling the 'CounterLog' with a message");
}
}
翻譯成 Java 程序是：
public class LogExample {
private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(LogExample.class.getName());
public static void main(String... args) {
log.error("Something's wrong here");
}
}
public class LogExampleOther {
private static final org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(LogExampleOther.class);
public static void main(String... args) {
log.error("Something else is wrong here");
}
}
public class LogExampleCategory {
private static final org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog("CounterLog");
public static void main(String... args) {
log.error("Calling the 'CounterLog' with a message");
}
}
