项目中经常使用bean，entity等类，绝大部分数据类类中都需要get、set、toString、equals和hashCode方法，虽然eclipse和idea开发环境下都有自动生成的快捷方式，但自动生成这些代码后，如果bean中的属性一旦有修改、删除或增加时，需要重新生成或删除get/set等方法，给代码维护增加负担。而使用了lombok则不一样，使用了lombok的注解(@Setter,@Getter,@ToString,@@RequiredArgsConstructor,@EqualsAndHashCode或@Data)之后，就不需要编写或生成get/set等方法，很大程度上减少了代码量，而且减少了代码维护的负担。故强烈建议项目中使用lombok，去掉bean中get、set、toString、equals和hashCode等方法的代码。
一、IDEA安装Lombok
安装过程如下图
2.png
1.png
安装完成后，重启IDEA即可。
二、在pom中添加依赖
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.20</version>
<scope>provided</scope>
</dependency>
三、Lombok常用注解
1、@Getter/@Setter注解为属性自动生成get/set方法。
@Setter
@Getter
public class User {
private Long id;
private String name;
private String password;
private String salt;
private Integer status;
private String address;
private String phone;
private Date lasttime;
}
2、@ToString注解，生成一个toString方法，默认的toString格式为：ClassName(fieldName= fieleValue ,fieldName1=fieleValue)。
@ToString
public class User {
private Long id;
private String name;
private String password;
private String salt;
private Integer status;
private String address;
private String phone;
private Date lasttime;
}
@ToString和下面的代码含义一样
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
", password='" + password + '\'' +
", salt='" + salt + '\'' +
", status=" + status +
", address='" + address + '\'' +
", phone='" + phone + '\'' +
", lasttime=" + lasttime +
'}';
}
3、Val将变量申明为final类型。
val defaultCount = new ArrayList<>();
// 下面的代码和上面的含义一样
final List<Integer> defaultCount = new ArrayList<>();
4、@NonNull注解能够为方法或构造函数的参数提供非空检查。
public void notNullExample(@NonNull String string) {
//方法内的代码
}
//=>上面代码相当于如下：
public void notNullExample(String string) {
if (string != null) {
//方法内的代码相当于如下：
} else {
throw new NullPointerException("null");
}
}
5、@Cleanup注解能够自动释放资源。
public void jedisExample(String[] args) {
try {
@Cleanup Jedis jedis = redisService.getJedis();
} catch (Exception ex) {
logger.error(“Jedis异常:”,ex)
}
//=>上面代码相当于如下：
Jedis jedis= null;
try {
jedis = redisService.getJedis();
} catch (Exception e) {
logger.error(“Jedis异常:”,ex)
} finally {
if (jedis != null) {
try {
jedis.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
6、@EqualsAndHashCode注解，自动生成equals和hashCode方法。
@EqualsAndHashCode(exclude = {"id"}, callSuper =true)
public class LombokDemo extends Demo{
private int id;
private String name;
private String gender;
}
//上面代码相当于如下：
public class LombokDemo extends Demo{
private int id;
private String name;
private String gender;
@Override
public boolean equals(final Object o) {
if (o == this) return true;
if (o == null) return false;
if (o.getClass() != this.getClass()) return false;
if (!super.equals(o)) return false;
final LombokDemo other = (LombokDemo)o;
if (this.name == null ? other.name != null : !this.name.equals(other.name)) return false;
if (this.gender == null ? other.gender != null : !this.gender.equals(other.gender)) return false;
return true;
}
@Override
public int hashCode() {
final int PRIME = 31;
int result = 1;
result = result * PRIME + super.hashCode();
result = result * PRIME + (this.name == null ? 0 : this.name.hashCode());
result = result * PRIME + (this.gender == null ? 0 : this.gender.hashCode());
return result;
}
}
7、@NoArgsConstructor, @RequiredArgsConstructor, @AllArgsConstructor,这几个注解分别自动生成了无参构造器、指定参数的构造器和包含所有参数的构造器。
@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;
}
}
//上面代码相当于如下：
@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;
}
}
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() {
}
}
}
8、@Data注解作用比较全，其包含注解的集合@ToString，@EqualsAndHashCode，所有字段的@Getter和所有非final字段的@Setter, @RequiredArgsConstructor。其示例代码可以参考上面几个注解的组合。
9、@Builder注解提供了一种比较推崇的构建值对象的方式。
@Builder
public class BuilderExample {
private String name;
private int age;
@Singular private Set<String> occupations;
}
//上面代码相当于如下：
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() {
Set<String> occupations = new HashSet<>();
return new BuilderExample(name, age, occupations);
}
@verride
public String toString() {
return "BuilderExample.BuilderExampleBuilder(name = " + this.name + ", age = " + this.age + ", occupations = " + this.occupations + ")";
}
}
}
10、@Synchronized注解类似Java中的Synchronized 关键字，但是可以隐藏同步锁。
public class SynchronizedExample {
private final Object readLock = new Object();
@Synchronized
public static void hello() {
System.out.println("world");
}
@Synchronized("readLock")
public void foo() {
System.out.println("bar");
}
//上面代码相当于如下：
public class SynchronizedExample {
private static final Object $LOCK = new Object[0];
private final Object readLock = new Object();
public static void hello() {
synchronized($LOCK) {
System.out.println("world");
}
}
public void foo() {
synchronized(readLock) {
System.out.println("bar");
}
}
}
