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 @NonNullprivate List<String> members;

等同于

@NonNullprivate List<String> members;@NonNullpublic 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。