Lombok的安装、使用说明

前言

以前写一个pojo的时候，我们可能需要为他设置getter 和setter方法，使用logger在程序中打印日志的时候我们可能需要new 一个logger的对象出来，使用tostring的时候我们可能需要复写一个类的tostring 方法。但是拥有了lombok我们就可以，不需要写这些那么繁琐的步骤了。

下载lombok的jar

下载的地址是：https://projectlombok.org/download.html

安装lombok

打开cmd 窗口，打开lombok 的目录，然后执行：

Java -jar lombok.jar

然后它会弹出个窗口，选择你的eclipse，点击安装就可以了，然后重启eclipse就可以使用了。

使用说明

@Getter and @Setter

可以很直观的从名字看出这个两个是分别用来生成Getter和Setter方法的

public class User{
    @Getter @Setter private boolean employed = true;
    @Setter(AccessLevel.PROTECTED) private String name;
}

相当于

public class User {
    private boolean employed = true;
    private String name;

    public User() {
    }

    public boolean isEmployed() {
        return this.employed;
    }

    public void setEmployed(boolean employed) {
        this.employed = employed;
    }

    protected void setName(String name) {
        this.name = name;
    }
}

@NonNull

提供一个参数的非空判断

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

等同于

@NonNull
private List<String> members;

@NonNull
public List<String> getMembers() {
    return this.members;
}

public void setMembers(@NonNull List<String> members) {
    if(members == null) {
        throw new NullPointerException("members");
    } else {
        this.members = members;
    }
}

@ToString

@ToString(exclude="name")
public class User {
    @Getter
    @Setter
    private boolean employed = true;
    @Setter(AccessLevel.PROTECTED)
    private String name;

    @Getter
    @Setter
    @NonNull
    private List<String> members;
}

等同于

public String toString() {
    return "User(employed=" + this.isEmployed() + ", members=" + this.getMembers() + ")";
}

@EqualsAndHashCode

@EqualsAndHashCode(exclude={"name"})
public class User {
    @Getter
    @Setter
    private boolean employed = true;
    @Setter(AccessLevel.PROTECTED)
    private String name;

    @Getter
    @Setter
    @NonNull
    private List<String> members;
}

等同于

public boolean equals(Object o) {
    if(o == this) {
        return true;
    } else if(!(o instanceof User)) {
        return false;
    } else {
        User other = (User)o;
        if(!other.canEqual(this)) {
            return false;
        } else if(this.isEmployed() != other.isEmployed()) {
            return false;
        } else {
            List this$members = this.getMembers();
            List other$members = other.getMembers();
            if(this$members == null) {
                if(other$members != null) {
                    return false;
                }
            } else if(!this$members.equals(other$members)) {
                return false;
            }

            return true;
        }
    }
}

public boolean canEqual(Object other) {
    return other instanceof User;
}

public int hashCode() {
    boolean PRIME = true;
    byte result = 1;
    int result1 = result * 59 + (this.isEmployed()?79:97);
    List $members = this.getMembers();
    result1 = result1 * 59 + ($members == null?0:$members.hashCode());
    return result1;
}

@Data

这个注解相当于同时使用@ToString, @EqualsAndHashCode, @Getter和@Setter

@Cleanup

他可以帮我们在需要释放的资源位置自动加上释放代码

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 e = new ByteArrayOutputStream();
        try {
            e.write(new byte[]{(byte)89, (byte)101, (byte)115});
            System.out.println(e.toString());
        } finally {
            if(Collections.singletonList(e).get(0) != null) {
                e.close();
            }
        }
    } catch (IOException var6) {
        var6.printStackTrace();
    }
}

@Synchronized

可以帮我们在方法上添加同步代码块

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

等同于

public class TestSync {
    private final Object $lock = new Object[0];
    private DateFormat format = new SimpleDateFormat("MM-dd-YYYY");
    public TestSync() {
    }
    public String synchronizedFormat(Date date) {
        Object var2 = this.$lock;
        synchronized(this.$lock) {
            return this.format.format(date);
        }
    }
}

总结

可以看到代码量差不多缩减了三倍，但是他也有一些缺点，比如：

大大降低了源代码文件的可读性和完整性，降低了阅读源代码的舒适度。