Lombok的正确打开方式
前言
本小结写一下Lombok。
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什么是Lombok
lombok是一个可以通过简单的注解的形式来帮助我们简化消除一些必须有但显得很臃肿的 Java 代码的工具，简单来说，比如我们新建了一个类，然后在其中写了几个字段，然后通常情况下我们需要手动去建立getter和setter方法啊，构造函数啊之类的，lombok的作用就是为了省去我们手动创建这些代码的麻烦，它能够在我们编译源码的时候自动帮我们生成这些方法。 -
怎么用
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Maven依赖
org.projectlombok lombok 你选择的版本 -
STS4
使用Eclipse或者对Eclipse做了高级封装的IDE需要在相应的ini配置文件中添加从Maven Repository中下载下来的Jar包，以本小结案例为例我下载到了本地磁盘中的：E:/WorkSpace/IDEs/MAVEN/RepositoryMicro/org/projectlombok/lombok/1.18.4/lombok-1.18.4.jar-startup plugins/org.eclipse.equinox.launcher_1.5.100.v20180827-1352.jar --launcher.library plugins/org.eclipse.equinox.launcher.win32.win32.x86_64_1.1.800.v20180827-1352 -product org.springframework.boot.ide.branding.sts4 --launcher.defaultAction openFile -vmargs -Dosgi.requiredJavaVersion=1.8 --add-modules=ALL-SYSTEM -Xms40m -Xmx1200m -Xbootclaspath/E:/WorkSpace/IDEs/MAVEN/RepositoryMicro/org/projectlombok/lombok/1.18.4/lombok-1.18.4.jar -javaagent:E:/WorkSpace/IDEs/MAVEN/RepositoryMicro/org/projectlombok/lombok/1.18.4/lombok-1.18.4.jar
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Lombok注解
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val：使用val作为局部变量声明的类型，而不是实际编写类型
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使用前
import java.util.ArrayList; import java.util.HashMap; import java.util.Map; public class ValExample { public String example() { final ArrayListexample = new ArrayList (); example.add("Hello, World!"); final String foo = example.get(0); return foo.toLowerCase(); } public void example2() { final HashMap -
使用后
import java.util.ArrayList; import java.util.HashMap; import lombok.val; public class ValExample { public String example() { val example = new ArrayList(); example.add("Hello, World!"); val foo = example.get(0); return foo.toLowerCase(); } public void example2() { val map = new HashMap
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var
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@NonNull：为注解的参数生成一个非空的检查，对于一般方法，检查语句将被插入到方法的最顶部，对于构造函数，检查语句将在任何显式this()和super()调用之后立即插入。
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使用前
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(); } } -
使用后
import lombok.NonNull; public class NonNullExample extends Something { private String name; public NonNullExample(@NonNull Person person) { super("Hello"); this.name = person.getName(); } }
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@Cleanup：自动管理(关闭)闭连接资源
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使用前
import java.io.*; 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(); } } } } -
使用后
import lombok.Cleanup; import java.io.*; 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); } } }
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@Getter/@Setter：为注解的字段生成get方法，@Setter：为注解的字段生成set方法，它的AccessLevel属性可以设置访问级别，如设置为PROTECTED，生成的set方法访问级别就是protected。
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使用前
public class GetterSetterExample { /** * Age of the person. Water is wet. */ private int age = 10; /** * Name of the person. */ private String name; @Override public String toString() { return String.format("%s (age: %d)", name, age); } /** * Age of the person. Water is wet. * * @return The current value of this person's age. Circles are round. */ public int getAge() { return age; } /** * Age of the person. Water is wet. * * @param age New value for this person's age. Sky is blue. */ public void setAge(int age) { this.age = age; } /** * Changes the name of this person. * * @param name The new value. */ protected void setName(String name) { this.name = name; } } -
使用后
import lombok.AccessLevel; import lombok.Getter; import lombok.Setter; public class GetterSetterExample { /** * Age of the person. Water is wet. * * @param age New value for this person's age. Sky is blue. * @return The current value of this person's age. Circles are round. */ @Getter @Setter private int age = 10; /** * Name of the person. * -- SETTER -- * Changes the name of this person. * * @param name The new value. */ @Setter(AccessLevel.PROTECTED) private String name; @Override public String toString() { return String.format("%s (age: %d)", name, age); } }
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@ToString：为注解的类生成toString字段，可以通过exculde属性设置哪些字段不在toString方法中。
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使用前
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.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) + ")"; } } -
使用后
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; } } }
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@EqualsAndHashCode(exclude = {“id”})：为注解的类生成equals和hashCode方法，可以通过exclude属性指定排除哪些属性不参与equals对比。
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使用前
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; } } } -
使用后
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; } } }
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@NoArgsConstructor：将生成一个无参的构造函数，如果你的变量中有被final修饰的，会报错，解决办法是添加force = true属性
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@RequiredArgsConstructor：将生成一个名为of的静态方法和一个protected修饰的构造函数，如果你的类中有final修饰的属性，该属性会当成of的入参
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@AllArgsConstructor(staticName=“of”)：将生成一个所有参数的构造函数。
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使用前
public class ConstructorExample{ private int x, y; @NonNull private T description; private ConstructorExample(T description) { if (description == null) throw new NullPointerException("description"); this.description = description; } public static ConstructorExample of(T description) { return new ConstructorExample (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() { } } } -
使用后
import lombok.AccessLevel; import lombok.RequiredArgsConstructor; import lombok.AllArgsConstructor; import lombok.NonNull; @RequiredArgsConstructor(staticName = "of") @AllArgsConstructor(access = AccessLevel.PROTECTED) public class ConstructorExample{ private int x, y; @NonNull private T description; @NoArgsConstructor public static class NoArgsExample { @NonNull private String field; } }
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@Data：相当于你在类上注解了@Getter/@Setter/@ToString/@EqualsAndHashCode，并且都是默认的参数。如果添加了staticConstructor="of"属性，则相当于还在类上添加了@RequireArgsConstructor(staticName = “of”)注解。
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使用前
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{ private final String name; private final T value; private Exercise(String name, T value) { this.name = name; this.value = value; } public static Exercise of(String name, T value) { return new Exercise (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; } } } -
使用后
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{ private final String name; private final T value; } }
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@Value：@Value是@Data的不可变的变体；默认情况下，所有字段都是私有的和最终的，并且不生成setter。
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使用前
import java.util.Arrays; 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 ^ $score); result = result * PRIME + Arrays.deepHashCode(this.getTags()); return result; } @java.lang.Override public String toString() { return "ValueExample(name=" + getName() + ", age=" + getAge() + ", score=" + getScore() + ", tags=" + Arrays.deepToString(getTags()) + ")"; } ValueExample withAge(int age) { return this.age == age ? this : new ValueExample(name, age, score, tags); } public static final class Exercise{ private final String name; private final T value; private Exercise(String name, T value) { this.name = name; this.value = value; } public static Exercise of(String name, T value) { return new Exercise (name, value); } public String getName() { return this.name; } public T getValue() { return this.value; } @java.lang.Override public boolean equals(Object o) { if (o == this) return true; if (!(o instanceof ValueExample.Exercise)) return false; final Exercise other = (Exercise)o; final Object this$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() + ")"; } } } -
使用后
import lombok.AccessLevel; import lombok.experimental.NonFinal; import lombok.experimental.Value; import lombok.experimental.Wither; import lombok.ToString; @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{ String name; T value; } }
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@Builder：为所在类生成复杂的生成器API。同时可以自动生成使类可实例化所需的代码。
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使用前
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 Setoccupations; } -
使用后
``` import java.util.Set; public class BuilderExample { private long created; private String name; private int age; private Setoccupations; BuilderExample(String name, int age, Set 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$set; private String name; private int age; private java.util.ArrayList occupations; BuilderExampleBuilder() { } public BuilderExampleBuilder created(long created) { this.created = created; this.created$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 (); } this.occupations.add(occupation); return this; } public BuilderExampleBuilder occupations(Collection occupations) { if (this.occupations == null) { this.occupations = new java.util.ArrayList (); } 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 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 + ")"; } } } ```
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@SneakyThrows：可用抛出检查异常(慎用)：
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使用前
``` import lombok.Lombok; 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); } } } ``` -
使用后
``` import lombok.SneakyThrows; 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(); } } ```
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@Synchronized：同步方法修饰符的更安全的变体。像synchronized一样，注释只能在静态和实例方法上使用
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使用前
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"); } } } -
使用后
import lombok.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"); } }
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@Getter(lazy=true)：生成一个getter，该getter将在第一次调用该getter时计算一个值，然后缓存它。
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使用前
public class GetterLazyExample { private final java.util.concurrent.AtomicReferencecached = new java.util.concurrent.AtomicReference (); 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; } } -
使用后
import lombok.Getter; 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; } }
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@Log：很多日志工具的集合注解。
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@CommonsLog
Creates private static final org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog(LogExample.class); -
@Flogger
Creates private static final com.google.common.flogger.FluentLogger log = com.google.common.flogger.FluentLogger.forEnclosingClass(); -
@JBossLog
Creates private static final org.jboss.logging.Logger log = org.jboss.logging.Logger.getLogger(LogExample.class); -
@Log
Creates private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(LogExample.class.getName()); -
@Log4j
Creates private static final org.apache.log4j.Logger log = org.apache.log4j.Logger.getLogger(LogExample.class); -
@Log4j2
Creates private static final org.apache.logging.log4j.Logger log = org.apache.logging.log4j.LogManager.getLogger(LogExample.class); -
@Slf4j
Creates private static final org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(LogExample.class); -
@XSlf4j
Creates private static final org.slf4j.ext.XLogger log = org.slf4j.ext.XLoggerFactory.getXLogger(LogExample.class); -
使用前
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.severe("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"); } } -
使用后
import lombok.extern.java.Log; import lombok.extern.slf4j.Slf4j; @Log public class LogExample { public static void main(String... args) { log.severe("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"); } }
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experimental：
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