lombok注解的使用

@Data 最常用注解

@Data public class Demo { private Long id; private String name; }

编译后

public class Demo { private Long id; private String name; public Demo() { } public Long getId() { return this.id; } public String getName() { return this.name; } public void setId(Long id) { this.id = id; } public void setName(String name) { this.name = name; } public boolean equals(Object o) { if (o == this) { return true; } else if (!(o instanceof Demo)) { return false; } else { Demo other = (Demo)o; if (!other.canEqual(this)) { return false; } else { Object this$id = this.getId(); Object other$id = other.getId(); if (this$id == null) { if (other$id != null) { return false; } } else if (!this$id.equals(other$id)) { return false; } Object this$name = this.getName(); Object other$name = other.getName(); if (this$name == null) { if (other$name != null) { return false; } } else if (!this$name.equals(other$name)) { return false; } return true; } } } protected boolean canEqual(Object other) { return other instanceof Demo; } public int hashCode() { int PRIME = true; int result = 1; Object $id = this.getId(); int result = result * 59 + ($id == null ? 43 : $id.hashCode()); Object $name = this.getName(); result = result * 59 + ($name == null ? 43 : $name.hashCode()); return result; } public String toString() { return "Demo(id=" + this.getId() + ", name=" + this.getName() + ")"; } }

@NonNull

public void setId(@NonNull Long id) { this.id = id; }

编译后

public void setId(@NonNull Long id) { if (id == null) { throw new NullPointerException("id"); } else { this.id = id; } }

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@RequiredArgsConstructor

@RequiredArgsConstructor public class Demo { @NonNull private Long id; private String name; }

编译后

public class Demo { @NonNull private Long id; private String name; public Demo(@NonNull Long id) { if (id == null) { throw new NullPointerException("id"); } else { this.id = id; } } }

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@NoArgsConstructor @AllArgsConstructor

@NoArgsConstructor @AllArgsConstructor public class Demo { @NonNull private Long id; private String name; }

编译后

public class Demo { @NonNull private Long id; private String name; public Demo() { } public Demo(@NonNull Long id, String name) { if (id == null) { throw new NullPointerException("id"); } else { this.id = id; this.name = name; } } }

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@Builder

单独使用时自动生成全参的构造器，没有默认构造器了，想要有非全参构造器必须与@AllArgsConstructor注解同时使用,然后手动或注解添加,否则将无法编译

@Builder public class Demo { @NonNull private Long id; private String name; }

编译后

public class Demo { @NonNull private Long id; private String name; Demo(@NonNull Long id, String name) { if (id == null) { throw new NullPointerException("id"); } else { this.id = id; this.name = name; } } public static Demo.DemoBuilder builder() { return new Demo.DemoBuilder(); } public static class DemoBuilder { private Long id; private String name; DemoBuilder() { } public Demo.DemoBuilder id(Long id) { this.id = id; return this; } public Demo.DemoBuilder name(String name) { this.name = name; return this; } public Demo build() { return new Demo(this.id, this.name); } public String toString() { return "Demo.DemoBuilder(id=" + this.id + ", name=" + this.name + ")"; } } }

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@Cleanup

自动调用close()

public static void main(String[] args) throws FileNotFoundException,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); } }

编译后

public static void main(String[] args) throws FileNotFoundException, IOException { FileInputStream in = new FileInputStream(args[0]); try { FileOutputStream out = new FileOutputStream(args[1]); try { byte[] b = new byte[10000]; while(true) { int r = in.read(b); if (r == -1) { return; } out.write(b, 0, r); } } finally { if (Collections.singletonList(out).get(0) != null) { out.close(); } } } finally { if (Collections.singletonList(in).get(0) != null) { in.close(); } } }

@Synchronized

给方法加锁

public class Demo { private final Object writeLock = new Object(); @Synchronized public static void method1(){ System.out.println("method1"); } @Synchronized public void method2(){ System.out.println("method1"); } @Synchronized("writeLock") public void method3(){ System.out.println("method1"); } }

编译后

public class Demo { private static final Object $LOCK = new Object[0]; private final Object $lock = new Object[0]; private final Object writeLock = new Object(); public Demo() { } public static void method1() { Object var0 = $LOCK; synchronized($LOCK) { System.out.println("method1"); } } public void method2() { Object var1 = this.$lock; synchronized(this.$lock) { System.out.println("method1"); } } public void method3() { Object var1 = this.writeLock; synchronized(this.writeLock) { System.out.println("method1"); } } }

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@Wither

给final赋值,必须有全参的构造器

@AllArgsConstructor public class Demo { @Wither private final int number; }

编译后

public class Demo { private final int number; public Demo(int number) { this.number = number; } public Demo withNumber(int number) { return this.number == number ? this : new Demo(number); } }

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@Log4j2@Log@Log4j@CommonsLog@Slf4j@XSLF4j

@Log4j2 public class Demo { public static void main(String[] args) { log.error("error"); } }

编译后

public class Demo { private static final Logger log = LogManager.getLogger(Demo.class); public Demo() { } public static void main(String[] args) { log.error("error"); } }