使用lombok提高编码效率

Lombok简介

Project Lombok makes java a spicier language by adding ‘handlers’ that know >how to build and compile simple, boilerplate-free, not-quite-java code.

github上官方是这么描述lombok的：

lombok项目通过增加处理程序使我们的java语言更加刺激（简洁和快速）。

先看个简单示例：

我们做java开发的时候，最不少写的就是javabean了，bean字段都需要添加gettter/setter方法，往往我们只能一次又一次的使用ide生成gettter，setter
构造器等等。

lombok是如何帮我们解决这种重复性劳动呢？

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package com.lhy.boot.lombok;

import lombok.Getter;

import lombok.Setter;

@Getter

@Setter

public class GetterSetterExample1 {

private int age = 10;

private String name ="张三丰";

private boolean registerd;

private String sex;

}

编译后的class：

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package com.lhy.boot.lombok;

public class GetterSetterExample1

{

private int age = 10;

private String name = "张三丰";

private boolean registerd;

private String sex;

public int getAge()

{

return this.age;

}

public String getName() {

return this.name;

}

public boolean isRegisterd() {

return this.registerd;

}

public String getSex() {

return this.sex;

}

public GetterSetterExample1 setAge(int age) {

this.age = age;

return this;

}

public GetterSetterExample1 setName(String name) {

this.name = name;

return this;

}

public GetterSetterExample1 setRegisterd(boolean registerd) {

this.registerd = registerd;

return this;

}

public GetterSetterExample1 setSex(String sex) {

this.sex = sex;

return this;

}

}

通过gettter，setter注解lombok已经帮我们自动生成了getter，setter方法！

是不是很神奇呢？lombok是怎么的做到的？这个后边再讲，先把lombok ide插件环境搭起来

下载并引用

maven项目添加依赖

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<dependency>

<groupId>org.projectlombok</groupId>

<artifactId>lombok</artifactId>

<version>1.16.16</version>

</dependency>

或者到官网下载jar包 https://projectlombok.org/download

安装ide插件

myeclipse/eclipse

下载完成后 命令行运行

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java -jar lombok-1.16.16.jar

弹出安装界面：



specify location 选择myeclipse安装目录，eclipse同理。

点击 install/update 安装完成。

或者将jar包放入myeclipse 根目录下

myeclipse.ini文件末尾添加：

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-javaagent:lombok-1.16.16.jar

重启myeclipse即可。

安装完毕后

打开myeclipse about 可以看到



证明插件安装完成

IntelliJ IDEA

定位到 File > Settings > Plugins

点击 Browse repositories…

搜索 Lombok Plugin

点击 Install plugin

重启 IDEA

Lombok注解详解

全局配置文件

我们可以从项目根目录下新建一个lombok.config（当然目录不是固定的，lombok会搜索所有lombok.config文件）

在这个文件加入一行

config.stopBubbling = true

表示该文件目录为根目录，lombok将从该目录下开始搜索。

每个子目录都可以配置lombok.config 作用范围只在该目录下，并且覆盖父目录的配置。

Lombok通常为所有生成的节点生成注释,添加@javax.annotation.Generated 。

可以用:

lombok.addJavaxGeneratedAnnotation = false 设置取消

下面看下lombok提供了哪些有趣的注解。

1.@val @var

使用Lombok ，java也能够像javascript一样使用弱类型定义变量了

val注解变量申明是final类型 var注解变量是非final类型

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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();

}

public void example2() {

val map = new HashMap<Integer, String>();

map.put(0, "zero");

map.put(5, "five");

for (val entry : map.entrySet()) {

System.out.printf("%d: %s\n", entry.getKey(), entry.getValue());

}

}

}

翻译后

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<span style="font-weight:normal;">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();

}

public void example2() {

final HashMap<Integer, String> map = new HashMap<Integer, String>();

map.put(0, "zero");

map.put(5, "five");

for (final Map.Entry<Integer, String> entry : map.entrySet()) {

System.out.printf("%d: %s\n", entry.getKey(), entry.getValue());

}

}

}</span>

2.@NonNull

在方法或构造函数的参数上使用@NonNull，lombok将生成一个空值检查语句。

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<span style="font-weight:normal;"> import lombok.NonNull;

public class NonNullExample extends Something {

private String name;

public NonNullExample(@NonNull Person person) {

super("Hello");

this.name = person.getName();

}

}</span>

翻译后

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<span style="font-weight:normal;">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();

}

}</span>

3.@Cleanup

使用该注解能够自动释放io资源

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<span style="font-weight:normal;"> 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);

}

}

}</span>

翻译后

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<span style="font-weight:normal;">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();

}

}

}

}</span>

当然从1.7开始jdk已经提供了try with resources的方式自动回收资源

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static String readFirstLineFromFile(String path) throws IOException {

try (BufferedReader br = new BufferedReader(new FileReader(path))) {

return br.readLine();

}

}

4.@Getter/@Setter

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<span style="font-weight:normal;">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);

}

}</span>

翻译后

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<span style="font-weight:normal;"> 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;

}

}</span>

扩展配置：

lombok.accessors.chain

= [

true

|

false

]
(default: false)如果设置为true，生成的setter将返回this(而不是void)，通过这个配置我们可以像jquery一样愉快的链式编程了。可以在类加增加一个@Accessors 注解 配置chain属性，优先于全局配置。

lombok.accessors.fluent

= [

true

|

false

]
(default: false)如果设置为true，生成的getter和setter将不会使用bean标准的get、is或set进行前缀;相反，方法将使用与字段相同的名称(减去前缀)。可以在类加增加一个@Accessors注解，配置fluent属性，优先于全局配置

lombok.accessors.prefix

+= a field prefix (default:
empty list)给getter/setter方法增加前缀 例如配置 +=M 原有的 getFoo方法将变为getMFoo方法。

lombok.getter.noIsPrefix

=
[

true

|

false

]
(default: false)如果设置为true，那么boolean型字段生成的getter将使用get前缀而不是默认的is前缀

5.@ToString

生成一个toString方法，log debug神器

默认的toString格式为：ClassName(fieldName= fieleValue ,fieldName1=fieleValue)

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<span style="font-weight:normal;">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.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;

}

}

}</span>

翻译后

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import java.util.Arrays;

ublic 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) + ")";

}

扩展配置：

lombok.toString.includeFieldNames

=
[

true

|

false

]
(default: true)

通常，lombok以fieldName=fieldValue的形式为每个字段生成一个toString响应的片段。如果设置为false，lombok将省略字段的名称，可以在该注解上配置属性includeFieldNames来标示包含的字段，这样可以覆盖默认配置。

lombok.toString.doNotUseGetters

=
[

true

|

false

]
(default: false)

如果设置为true，lombok将直接访问字段，而不是在生成tostring方法时使用getter(如果可用)。可以在该注解上配置属性doNotUseGetters来标示不使用getter的字段，这样可以覆盖默认配置。

6.@EqualsAndHashCode

给类增加equals和hashCode方法

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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;

}

}

}

翻译后

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import java.util.Arrays;

ublic 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;

}

}

扩展配置：

lombok.config增加：

lombok.equalsAndHashCode.doNotUseGetters

=
[

true

|

false

]
(default: false)如果设置为true，lombok将直接访问字段，而不是在生成equals和hashcode方法时使用getter(如果可用)。

可以在该注解上配置属性donotusegetter来标示不使用getter的字段，这样可以覆盖默认配置。

lombok.equalsAndHashCode.callSuper

=
[

call

|

skip

|

warn

]
(default: warn)如果设置为call，lombok将生成对hashCode的超类实现的调用。如果设置为skip，则不会生成这样的调用。默认行为warn类似于skip，并带有附加警告。

7.@NoArgsConstructor, @RequiredArgsConstructor and @AllArgsConstructor

给类增加无参构造器 指定参数的构造器 包含所有参数的构造器

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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;

}

}

翻译后

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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() {

}

}

}

扩展配置：

lombok.anyConstructor.suppressConstructorProperties

=
[

true

|

false

]
(default:

false

)如果将其设置为true，那么lombok将跳过添加一个@java.bean.ConstructorProperties生成的构造器。这在android和GWT开发中很有用，因为这些注释通常不可用。

8.@Data

包含以下注解的集合

@ToString,@EqualsAndHashCode,所有字段的 @Getter 所有非final字段的@Setter ，@RequiredArgsConstructor

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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;

}

}

翻译后

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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;

}

}

}

9.@Value

@value是@data的不可变对象 （不可变对象的用处和创建：https://my.oschina.net/jasonultimate/blog/166810）

所有字段都是私有的，默认情况下是final的，并且不会生成setter。默认情况下，类本身也是final的，因为不可变性不能强制转化为子类。与@data一样，有用toString()、equals()和hashCode()方法也是生成的，每个字段都有一个getter方法，并且一个覆盖每个参数的构造器也会生成。

10.@Builder

建筑者模式

是现在比较推崇的一种构建值对象的方式。

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import lombok.Builder;

import lombok.Singular;

import java.util.Set;

@Builder

public class BuilderExample {

private String name;

private int age;

@Singular private Set<String> occupations;

}

翻译后

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import java.util.Set;

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 + ")";

}

}

}

11.@SneakyThrows

把checked异常转化为unchecked异常，好处是不用再往上层方法抛出了，美其名曰暗埋异常

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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();

}

}

翻译后：

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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);

}

}

}

12.@Synchronized

类似于Synchronized 关键字 但是可以隐藏同步锁

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import lombok.Synchronized;

ublic 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");

}

翻译后

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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");

}

}

}

xianzjdk推荐使用Lock了，这个仅供参考

13.@Getter(lazy=true)

如果getter方法计算值需要大量CPU，或者值占用大量内存，第一次调用这个getter，它将一次计算一个值，然后从那时开始缓存它

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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;

}

}

翻译后

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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;

}

14.@Log

可以生成各种log对象，方便多了

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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");

}

}

翻译为

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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");

}

}

所有支持的log类型：

@CommonsLog

Creates

private static final org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog(LogExample.class);

@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);

扩展配置：

lombok.log.fieldName

= an
identifier (default:

log

).生成log字段的名称
默认为log

lombok.log.fieldIsStatic

=
[

true

|

false

]
(default: true)生成log是否是static的 默认为static

官方文档说明：https://projectlombok.org/features/all

Lombok原理

lombok通过简单的注解标志就能够实现复杂的代码生成，他是怎么做到的？

lombok注解不是我们常见的runtime注解，而是source注解或者class注解，

在没有jsr之前我们可以通过反射在运行是获取注解值，但是这样效率很低，而且没办法做到编译检查，对开发人员一些不合的编码错误给出警告，

JSR 269: Pluggable Annotation Processing API (https://www.jcp.org/en/jsr/detail?id=269)
出现后，我们可以在javac的编译器利用注解来完成对class文件的修改。



lombok本质上就是这样的一个实现了"JSR 269 API"的程序。在使用javac的过程中，它产生作用的具体流程如下：

1)javac对源代码进行分析，生成一棵抽象语法树(AST)

2)运行过程中调用实现了"JSR 269 API"的lombok程序

3)此时lombok就对第一步骤得到的AST进行处理，找到@Data注解所在类对应的语法树(AST)，然后修改该语法树(AST)，增加getter和setter方法定义的相应树节点

4)javac使用修改后的抽象语法树(AST)生成字节码文件，即给class增加新的节点（代码块）

ide中使用Lombok的注意事项

1.项目中要使用lombok 不仅ide要支持（否则一堆错误），项目中也要引入jar包

2.如果配置lombok.config文件，修改文件的属性值后，并不会自动重新编译class文件，ide编辑器也不会自动更新，所有每次修改配置文件后最后关闭java文件窗口重新打开，并且clean下项目

官方文档说明：https://projectlombok.org/features/all

来源：http://blog.csdn.net/v2sking/article/details/73431364