lombok使用總結
前提
這篇文章主要介紹lombok的使用，至於lombok的源碼和原理暫不探究，可以看上一篇文章插件化註解處理API去了解lombok的基本原理。參考資料：
簡介
Project Lombok是一個java庫，它可以自動插入到編輯器中，並構建工具，使java更加豐富。再也不用getter或equals方法了。儘早訪問未來的java特性，比如val等等。這個就是lombok的官方簡介(例如Jdk9中新增的val關鍵字在lombok中很早就出現了)。lombok實際上是基於JSR-269的插件化註解處理API，在編譯期間對使用了特定註解的類、方法、屬性或者代碼片段進行動態修改，添加或者實現其自定義功能的類庫。
安裝
maven依賴
在項目中使用到lombok的註解必須引入其依賴：
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${version}</version>
</dependency>
插件
如果不爲IDE安裝lombok的插件，IDE無法識別lombok編譯期動態生成的代碼，表現爲代碼塊標紅，因此需要安裝其插件，插件地址：https://projectlombok.org/download。
下載完成後，將會得到一個jar包lombok-xx.xx.xx.jar，直接使用命令java -jar lombok-xx.xx.xx.jar運行即可，然後按照指引安裝到IDEA、eclipse或者myeclipse。
lombok註解
@val
@val用於聲明修飾符爲final的局部變量類型，使用的時候不需要編寫實際的類型，這一點依賴於編譯器的類型推導。@val的作用域是局部變量。舉例如下：
使用lombok：
import java.util.ArrayList;
import java.util.HashMap;
import lombok.val;
public class ValExample {
public String example() {
val example = new ArrayList<String>();
example.add("Hello, World!");
val foo = example.get(0);
return foo.toLowerCase();
}
}
相當於原生Java：
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
public class ValExample {
public String example() {
final ArrayList<String> example = new ArrayList<String>();
example.add("Hello, World!");
final String foo = example.get(0);
return foo.toLowerCase();
}
}
@var
@var的功能類似於@val，不過@var修飾的是非final修飾的局部變量。
@NonNull
@NonNull的作用域是屬性(field)、方法參數或、構造函數參數以及局部變量(LOCAL_VARIABLE)，爲這些參數添加一個空檢查語句，基本格式是：if(param == null) {throw new NullPointerException("param ");}。使用lombok：
import lombok.NonNull;
public class NonNullExample extends Something {
private String name;
public NonNullExample(@NonNull Person person) {
super("Hello");
this.name = person.getName();
}
}
相當於原生Java：
import lombok.NonNull;
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();
}
}
@Cleanup
你可以使用@Cleanup來確保在代碼執行路徑退出當前範圍之前自動清理給定的資源，一般使用在流的局部變量的關閉。可以通過value()指定關閉資源的方法名，注意，關閉資源的方法必須是無參void方法，默認的關閉資源方法名稱是"close"。使用lombok：
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);
}
}
}
相當於原生Java：
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();
}
}
}
}
@Getter/@Setter
@Getter/@Setter作用域是屬性或者類。@Getter爲指定屬性或者類中的所有屬性生成Getter方法，@Setter指定非final屬性或者類中的所有非final屬性生成Setter方法。可以通過@Getter/@Setter的value()中的AccessLevel屬性來指定生成的方法的修飾符，可以通過@Getter的布爾值屬性lazy來指定是否延遲加載。使用lombok：
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);
}
}
相當於原生Java：
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;
}
}
@ToString
@ToString的作用域是類，主要作用是覆蓋類中的toString方法。@ToString的屬性比較多，簡介如下：
- includeFieldNames()：布爾值，默認爲true，true表示拼接toString的時候使用屬性名。
- exclude()：字符串數組，默認爲空，用於通過屬性名排除拼接toString時使用的屬性。
- of()：exclude()屬性的對立屬性，意思就是include。
- callSuper()：布爾值，默認爲false，是否調用父類的屬性。
- doNotUseGetters()：布爾值，默認爲false，true表示拼接toString的時候使用屬性值而不是其Getter方法。
下面是官方例子：使用lombok：
import lombok.ToString;
@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.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;
}
}
}
相當於原生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.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) + ")";
}
}
@EqualsAndHashCode
@EqualsAndHashCode的作用域是類，用於生成equals()和hashCode()方法。此註解的屬性比較多，不過和@ToString類似。舉例如下：使用lombok：
import lombok.EqualsAndHashCode;
@EqualsAndHashCode(exclude={"id", "shape"})
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;
}
@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;
}
}
}
相當於原生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;
}
}
}
@NoArgsConstructor, @RequiredArgsConstructor, @AllArgsConstructor
這三個註解的作用域都是類。@NoArgsConstructor作用是生成一個無參數的構造函數。@AllArgsConstructor作用是生成一個具有所有字段的構造函數。@RequiredArgsConstructor的作用是爲每一個使用了final或者@NonNull修飾的屬性都生成一個只有一個參數的構造函數。這三個註解都可以通過staticName()指定構造的命名，通過access()指定構造的修飾符。@NoArgsConstructor的屬性force()默認值爲false，當類中存在final屬性的時候使用了@NoArgsConstructor會編譯錯誤，如果force()值爲true，那麼會把final修飾的屬性作爲"無參數構造"的參數，並且把屬性賦值爲0、null或者false。使用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;
}
}
相當於原生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() {
}
}
}
@Data
@Data的作用域是類，相當於同時應用了@Getter、@Setter、@ToString、@EqualsAndHashCode、@RequiredArgsConstructor。如果已經顯示自定義過構造函數，就不會再自動生成構造函數了。舉例如下：使用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;
}
}
相當於原生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;
}
}
}
@Value
@Value的作用域是類，和@Data類似，但是用於不可變類型。生成的類和所有字段都設置爲final，所有字段都爲private，自動生成Getter但是沒有Setter，會生成初始化所有字段的構造函數。相當於同時應用了final、 @ToString、 @EqualsAndHashCode、 @AllArgsConstructor 、@FieldDefaults(makeFinal = true, level = AccessLevel.PRIVATE)和@Getter。
使用lombok：
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<T> {
String name;
T value;
}
}
相當於原生Java：
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 ^ $score);
result = result * PRIME + Arrays.deepHashCode(this.getTags());
return result;
}
@java.lang.Override
public String toString() {
return "ValueExample(name=" + getName() + ", age=" + getAge() + ", score=" + getScore() + ", tags=" + Arrays.deepToString(getTags()) + ")";
}
ValueExample withAge(int age) {
return this.age == age ? this : new ValueExample(name, age, score, tags);
}
public static final class Exercise<T> {
private final String name;
private final T value;
private Exercise(String name, T value) {
this.name = name;
this.value = value;
}
public static <T> Exercise<T> of(String name, T value) {
return new Exercise<T>(name, value);
}
public String getName() {
return this.name;
}
public T getValue() {
return this.value;
}
@java.lang.Override
public boolean equals(Object o) {
if (o == this) return true;
if (!(o instanceof ValueExample.Exercise)) return false;
final Exercise<?> other = (Exercise<?>)o;
final Object this$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() + ")";
}
}
}
@Builder
@Builder的作用域是類，使用此註解後類中新增一個成員類(Builder)將會使用構建者模式，編譯時增加了一個Builder內部類和全字段的構造器。@Builder.Default用於指定Builder中的屬性的默認值，@Singular用於告訴lombok當前屬性類型是集合類型，lombok會爲信任的集合類型添加"adder"方法而不是"setter"方法。使用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;
}
相當於原生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 + ")";
}
}
}
@Synchronized
@Synchronized的作用域是方法，用於方法同步，使用此註解後，方法體中的代碼塊自動包含在一個synchronize塊中。synchronize塊加鎖的對象一定是類中的一個成員屬性，可以通過@Synchronized的value()指定，如果不存在則由lombok新建，一般是private final Object $lock = new Object[0];。使用lombok：
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");
}
}
相當於原生Java：
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");
}
}
}
@SneakyThrows
@SneakyThrows的作用域是構造或者方法，用於自動捕獲(隱藏)檢查異常。我們知道，java對於檢查異常，需要在編碼時進行捕獲，或者拋出。該註解的作用是將檢查異常包裝爲運行時異常，那麼編碼時就無需處理異常了。
提示：不過這並不是友好的編碼方式，因爲你編寫的api的使用者，不能顯式的獲知需要處理檢查異常。
使用lombok：
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();
}
}
相當於原生Java：
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);
}
}
}
@Log
@Log的作用域是類，用於生成日誌API句柄。目前支持的類型如下：
@CommonsLog
相當於在類中定義了：private static final org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog(LogExample.class);
@JBossLog
相當於在類中定義了：private static final org.jboss.logging.Logger log = org.jboss.logging.Logger.getLogger(LogExample.class);
@Log
相當於在類中定義了：private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(LogExample.class.getName());
@Log4j
相當於在類中定義了：private static final org.apache.log4j.Logger log = org.apache.log4j.Logger.getLogger(LogExample.class);
@Log4j2
相當於在類中定義了：private static final org.apache.logging.log4j.Logger log = org.apache.logging.log4j.LogManager.getLogger(LogExample.class);
@Slf4j
相當於在類中定義了：private static final org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(LogExample.class);
@XSlf4j
相當於在類中定義了：private static final org.slf4j.ext.XLogger log = org.slf4j.ext.XLoggerFactory.getXLogger(LogExample.class);
使用lombok：
import lombok.extern.java.Log;
import lombok.extern.slf4j.Slf4j;
@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");
}
}
相當於原生Java：
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");
}
}