lombok既是一个IDE插件,也是一个项目要依赖的jar包.lombok是依赖jar包的原因是因为编译时要用它的注解.是插件的原因是他要在编译器编译时通过操作AST(抽象语法树)改变字节码生成.也就是说他可以改变java语法. 他不像spring的依赖注入或者hibernate的orm一样是运行时的特性,而是编译时的特性.
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？
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：
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
<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
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：
-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
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
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());
}
}
}
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。
import lombok.NonNull;
public class NonNullExample extends Something {
private String name;
public NonNullExample(@NonNull Person person) {
super("Hello");
this.name = person.getName();
}
}
翻译后
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();
}
}
3.@Cleanup
使用该注解能够自动释放io资源
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);
}
}
}
翻译后
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();
}
}
}
}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
static String readFirstLineFromFile(String path) throws IOException {
try (BufferedReader br = new BufferedReader(new FileReader(path))) {
return br.readLine();
}
}
4.@Getter/@Setter
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);
}
}
翻译后
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;
}
}
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)
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;
}
}
}
翻译后
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) + ")";
}
}
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
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
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;
}
}
}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
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
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
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
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：）
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。
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
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
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：
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
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");
}
}
翻译后
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
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
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
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
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
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