# Lombok 应用指南 * [1. Lombok 简介](#1-lombok-简介) * [2. Lombok 安装](#2-lombok-安装) * [3. Lombok 使用](#3-lombok-使用) * [3.1. @Getter and @Setter](#31-getter-and-setter) * [3.2. @NonNull](#32-nonnull) * [3.3. @ToString](#33-tostring) * [3.4. @EqualsAndHashCode](#34-equalsandhashcode) * [3.5. @Data](#35-data) * [3.6. @Cleanup](#36-cleanup) * [3.7. @Synchronized](#37-synchronized) * [3.8. @SneakyThrows](#38-sneakythrows) * [3.9. 示例源码](#39-示例源码) * [4. 参考资料](#4-参考资料) ## 1. Lombok 简介 Lombok 是一种 Java 实用工具，可用来帮助开发人员消除 Java 的冗长，尤其是对于简单的 Java 对象（POJO）。它通过注释实现这一目的。通过在开发环境中实现 Lombok，开发人员可以节省构建诸如 `hashCode()` 和 `equals()` 、`getter / setter` 这样的方法以及以往用来分类各种 accessor 和 mutator 的大量时间。 ## 2. Lombok 安装 使 IntelliJ IDEA 支持 Lombok 方式如下： * **Intellij 设置支持注解处理** * 点击 File > Settings > Build > Annotation Processors * 勾选 Enable annotation processing * **安装插件** * 点击 Settings > Plugins > Browse repositories * 查找 Lombok Plugin 并进行安装 * 重启 IntelliJ IDEA * **将 lombok 添加到 pom 文件** ```markup org.projectlombok lombok 1.16.8 ``` ## 3. Lombok 使用 Lombok 提供注解 API 来修饰指定的类： ### 3.1. @Getter and @Setter [@Getter and @Setter](http://jnb.ociweb.com/jnb/jnbJan2010.html#gettersetter) Lombok 代码： ```java @Getter @Setter private boolean employed = true; @Setter(AccessLevel.PROTECTED) private String name; ``` 等价于 Java 源码： ```java 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; } ``` ### 3.2. @NonNull [@NonNull](http://jnb.ociweb.com/jnb/jnbJan2010.html#nonnull) Lombok 代码： ```java @Getter @Setter @NonNull private List members; ``` 等价于 Java 源码： ```java @NonNull private List members; public Family(@NonNull final List members) { if (members == null) throw new java.lang.NullPointerException("members"); this.members = members; } @NonNull public List getMembers() { return members; } public void setMembers(@NonNull final List members) { if (members == null) throw new java.lang.NullPointerException("members"); this.members = members; } ``` ### 3.3. @ToString [@ToString](http://jnb.ociweb.com/jnb/jnbJan2010.html#tostring) Lombok 代码： ```java @ToString(callSuper=true,exclude="someExcludedField") public class Foo extends Bar { private boolean someBoolean = true; private String someStringField; private float someExcludedField; } ``` 等价于 Java 源码： ```java 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 + ")"; } } ``` ### 3.4. @EqualsAndHashCode [@EqualsAndHashCode](http://jnb.ociweb.com/jnb/jnbJan2010.html#equals) Lombok 代码： ```java @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; } ``` 等价于 Java 源码： ```java 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; } } ``` ### 3.5. @Data [@Data](http://jnb.ociweb.com/jnb/jnbJan2010.html#data) Lombok 代码： ```java @Data(staticConstructor="of") public class Company { private final Person founder; private String name; private List employees; } ``` 等价于 Java 源码： ```java public class Company { private final Person founder; private String name; private List 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 getEmployees() { return employees; } public void setEmployees(final List 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 + ")"; } } ``` ### 3.6. @Cleanup [@Cleanup](http://jnb.ociweb.com/jnb/jnbJan2010.html#cleanup) Lombok 代码： ```java 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(); } } ``` 等价于 Java 源码： ```java 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(); } } ``` ### 3.7. @Synchronized [@Synchronized](http://jnb.ociweb.com/jnb/jnbJan2010.html#synchronized) Lombok 代码： ```java private DateFormat format = new SimpleDateFormat("MM-dd-YYYY"); @Synchronized public String synchronizedFormat(Date date) { return format.format(date); } ``` 等价于 Java 源码： ```java 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); } } ``` ### 3.8. @SneakyThrows [@SneakyThrows](http://jnb.ociweb.com/jnb/jnbJan2010.html#sneaky) Lombok 代码： ```java @SneakyThrows public void testSneakyThrows() { throw new IllegalAccessException(); } ``` 等价于 Java 源码： ```java public void testSneakyThrows() { try { throw new IllegalAccessException(); } catch (java.lang.Throwable $ex) { throw lombok.Lombok.sneakyThrow($ex); } } ``` ### 3.9. 示例源码 > 示例源码：[javalib-bean](https://github.com/dunwu/java-tutorial/tree/master/javalib-bean) ## 4. 参考资料 * [Lombok 官网](https://projectlombok.org/) * [Lombok Github](https://github.com/rzwitserloot/lombok) * [IntelliJ IDEA - Lombok Plugin](http://plugins.jetbrains.com/plugin/6317-lombok-plugin)