Project Lombok （即 Lombok）学习记录

标签：return name 记录 private Project Lombok null public String

参考文档
什么是 Project Lombok ？
下载 Project Lombok
支持的安装方式
安装 Project Lombok
使用 Project Lombok
Lombok 提供的注解

参考文档

什么是 Project Lombok ？

Project Lombok is a java library that automatically plugs into your editor and build tools, spicing up your java.
Never write another getter or equals method again, with one annotation your class has a fully featured builder, Automate your logging variables, and much more.

Project Lombok是一个java库，它可以自动插入编辑器和构建工具，增加java的趣味性。
永远不要再写另一个 getter 或 equals 方法，只需一个注释，你的类就有了一个功能齐全的构建器，自动化你的日志变量，等等。

总结：使用注解即可替换 getter setter equals 等方法，在编译期自动生成生成getter setter equals 等方法代码。

下载 Project Lombok

下载页面：https://projectlombok.org/download
下载地址：https://projectlombok.org/downloads/lombok.jar
历史版本：https://projectlombok.org/all-versions

支持的安装方式

安装 Project Lombok

lombok.jar 安装

依赖：必须保证安装JDK并配置环境变量

windos 打开 CMD命令窗口，执行下面命令执行安装：

java -jar lombok.jar

lombok 会自动扫描已安装的 IDE 开发工具：

如果IDE 不是 exe 安装的，则lombok会找不到已安装的IDE：

这时，点击【Specify location ...】按钮，自行选择 IDE 开发工具的程序（我本地是 eclipse）：

继续点击【Install / Update】按钮进行安装。
安装完成后，：

至此，安装完成。后续步骤：

之后需要将 lombok.jar 添加到你的项目中。

eclipse 安装 lombok 插件

两种方式：

使用 lombok.jar 安装，选择本机的 eclipse
使用 eclipse 市场安装插件 https://projectlombok.org/p2

IntelliJ 安装 lombok 插件

步骤：

选择 File > Settings > Plugins
点击 Browse repositories...
查找 Lombok 插件
点击 Install plugin
重启 IntelliJ IDEA

使用 Project Lombok

新建 maven 项目
引入 lombok.jar

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.24</version>
    <scope>provided</scope>
</dependency>

编写标注 lombok注解的 Response.java 类

import java.io.Serializable;

import lombok.Builder;
import lombok.Data;

@Data
@Builder
public class Response implements Serializable {

    private static final long serialVersionUID = 5001615840097014470L;

    private String code;

    private boolean success;

    private String message;
}

eclipse 中使用 “Ctrl + o” 快捷键查看类结构：

注意：@Builder 会把无参构造方法私有化！

Lombok 提供的注解

@GETTER AND @SETTER

@GETTER 和 @SETTER 注解依次生成get，set方法。
例子：

@Getter @Setter private boolean employed = true;
@Setter(AccessLevel.PROTECTED) private String name;

等同于

private boolean employed = true;
private String name;
 
public boolean isEmployed() {
    return employed;
}
 
public void setEmployed(final boolean employed) {
    this.employed = employed;
}
 
protected void setName(final String name) {
    this.name = name;
}

@NONNULL

@NONNULL 表明为类的成员添加空指针校验。

例子：

@Getter @Setter @NonNull
private List<Person> members;

等同于

@NonNull
private List<Person> members;
 
public Family(@NonNull final List<Person> members) {
    if (members == null) throw new java.lang.NullPointerException("members");
    this.members = members;
}
 
@NonNull
public List<Person> getMembers() {
    return members;
}
 
public void setMembers(@NonNull final List<Person> members) {
    if (members == null) throw new java.lang.NullPointerException("members");
    this.members = members;
}

@TOSTRING

@TOSTRING 注解生成 toString方法的实现。
例子：

@ToString(callSuper=true,exclude="someExcludedField")
public class Foo extends Bar {
    private boolean someBoolean = true;
    private String someStringField;
    private float someExcludedField;
}

等同于

public class Foo extends Bar {
    private boolean someBoolean = true;
    private String someStringField;
    private float someExcludedField;
 
    @java.lang.Override
    public java.lang.String toString() {
        return "Foo(super=" + super.toString() +
            ", someBoolean=" + someBoolean +
            ", someStringField=" + someStringField + ")";
    }
}

@EQUALSANDHASHCODE

@EQUALSANDHASHCODE 注解会指示 Lombok 生成 equals 和 hashCode 方法。

例子：

@EqualsAndHashCode(callSuper=true,exclude={"address","city","state","zip"})
public class Person extends SentientBeing {
    enum Gender { Male, Female }
 
    @NonNull private String name;
    @NonNull private Gender gender;
 
    private String ssn;
    private String address;
    private String city;
    private String state;
    private String zip;
}

等同于

public class Person extends SentientBeing {
 
    enum Gender {
        /*public static final*/ Male /* = new Gender() */,
        /*public static final*/ Female /* = new Gender() */;
    }
    @NonNull
    private String name;
    @NonNull
    private Gender gender;
    private String ssn;
    private String address;
    private String city;
    private String state;
    private String zip;
 
    @java.lang.Override
    public boolean equals(final java.lang.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 Person other = (Person)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;
        if (this.ssn == null ? other.ssn != null : !this.ssn.equals(other.ssn)) return false;
        return true;
    }
 
    @java.lang.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());
        result = result * PRIME + (this.ssn == null ? 0 : this.ssn.hashCode());
        return result;
    }
}

@DATA

@Data 注解相当于 @ToString, @EqualsAndHashCode, @Getter 和 @Setter 注解的集合。

例子：

@Data(staticConstructor="of")
public class Company {
    private final Person founder;
    private String name;
    private List<Person> employees;
}

等同于

public class Company {
    private final Person founder;
    private String name;
    private List<Person> employees;
 
    private Company(final Person founder) {
        this.founder = founder;
    }
 
    public static Company of(final Person founder) {
        return new Company(founder);
    }
 
    public Person getFounder() {
        return founder;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(final String name) {
        this.name = name;
    }
 
    public List<Person> getEmployees() {
        return employees;
    }
 
    public void setEmployees(final List<Person> employees) {
        this.employees = employees;
    }
 
    @java.lang.Override
    public boolean equals(final java.lang.Object o) {
        if (o == this) return true;
        if (o == null) return false;
        if (o.getClass() != this.getClass()) return false;
        final Company other = (Company)o;
        if (this.founder == null ? other.founder != null : !this.founder.equals(other.founder)) return false;
        if (this.name == null ? other.name != null : !this.name.equals(other.name)) return false;
        if (this.employees == null ? other.employees != null : !this.employees.equals(other.employees)) return false;
        return true;
    }
 
    @java.lang.Override
    public int hashCode() {
        final int PRIME = 31;
        int result = 1;
        result = result * PRIME + (this.founder == null ? 0 : this.founder.hashCode());
        result = result * PRIME + (this.name == null ? 0 : this.name.hashCode());
        result = result * PRIME + (this.employees == null ? 0 : this.employees.hashCode());
        return result;
    }
 
    @java.lang.Override
    public java.lang.String toString() {
        return "Company(founder=" + founder + ", name=" + name + ", employees=" + employees + ")";
    }
}

@CLEANUP

@Cleanup 注解用于确保分配的资源能够释放掉。如果本地变量标记了 @Cleanup 注解，则子代码将会被 try/finally 块包围住。

例子：

public void testCleanUp() {
    try {
        @Cleanup ByteArrayOutputStream baos = new ByteArrayOutputStream();
        baos.write(new byte[] {'Y','e','s'});
        System.out.println(baos.toString());
    } catch (IOException e) {
        e.printStackTrace();
    }
}

等同于

public void testCleanUp() {
    try {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            baos.write(new byte[]{'Y', 'e', 's'});
            System.out.println(baos.toString());
        } finally {
            baos.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

@SYNCHRONIZED

@Synchronized 注解在方法内添加 synchronized 同步代码块。

private DateFormat format = new SimpleDateFormat("MM-dd-YYYY");
 
@Synchronized
public String synchronizedFormat(Date date) {
    return format.format(date);
}

等同于

private final java.lang.Object $lock = new java.lang.Object[0];
private DateFormat format = new SimpleDateFormat("MM-dd-YYYY");
 
public String synchronizedFormat(Date date) {
    synchronized ($lock) {
        return format.format(date);
    }
}

@SNEAKYTHROWS

@SneakyThrows 注解是为了解决抛出异常时 IDE 提示“Unhandled exception ...”：

@SneakyThrows 注解实际就是抛出异常包装成 RuntimeException。

@SneakyThrows 注解加在方法上：

@SneakyThrows
public void testSneakyThrows() {
    throw new IllegalAccessException();
}

等同于：

public void testSneakyThrows() {
    try {
        throw new IllegalAccessException();
    } catch (java.lang.Throwable $ex) {
        throw lombok.Lombok.sneakyThrow($ex);
    }
}

sneakyThrow 方法:

public static RuntimeException sneakyThrow(Throwable t) {
    if (t == null) throw new NullPointerException("t");
    return Lombok.<RuntimeException>sneakyThrow0(t);
}

@SuppressWarnings("unchecked")
private static <T extends Throwable> T sneakyThrow0(Throwable t) throws T {
    throw (T)t;
}

标签：return,name,记录,private,Project,Lombok,null,public,String
From： https://www.cnblogs.com/lihw-study/p/16280912.html