官網地址:https://projectlombok.orgjava
官網的首頁視頻演示在eclipse中如何使用Lombok;git
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.github
翻譯:spring
Lombok項目是一個java的庫,能夠自動的經過插件的方式安裝到你的編輯器和構建工具中,給你的Java代碼調味,不再用寫 getter和equals方法了,經過一個類上的註解你擁有了建造者的特徵,自動的聲明瞭一個日誌變量,還有更多功能;springboot
自由使用final本地變量;
從0.10版本開始引入
你能夠使用val做爲本地變量的申明,來替代寫它的實際類型。若是你這樣作了,類型將會從初始化表達式中被推斷,本地變量也會被設置爲final,這個特徵工做在以下場景:
1.本地變量;
2.foreach循環;
在類的成員中並不會生效,初始化表達式是須要的。
val其實是一個類型的排序,做爲一個真實的類存在於lombok的包中,你必須引入val才能工做(或者使用lombok.val做爲類型),在本地變量聲明中這種類型的存在會觸發兩個操做:
1.增長final關鍵字;
2.複製初始化表達式的類型,用來重寫這個僞造的val類型;
注意這個功能在netbeans中不會起做用;app
注意事項:eclipse
對於混合的類型,會推斷獲得公共的父類,而不是共享的接口。
在含糊的場景下:若是初始化爲null,會推斷獲得Object.編輯器
實例代碼:不適用lombok;ide
package com.springpractice._val; import java.util.ArrayList; import java.util.HashMap; import java.util.Map; /** * Hello world! */ public class App { public String test1() { final ArrayList<String> exampleList = new ArrayList<>(); exampleList.add("hello world"); final String firstElement = exampleList.get(0); final String returnString = firstElement.toLowerCase(); System.out.println(returnString); return returnString; } public void test2() { final HashMap<Integer, String> map = new HashMap<>(); map.put(0, "zero"); map.put(5, "five"); for (final Map.Entry<Integer, String> entry : map.entrySet()) { System.out.printf("%d: %s \n", entry.getKey(), entry.getValue()); } } public static void main(String[] args) { final App app = new App(); app.test1(); System.out.println("======"); app.test2(); } }
使用lombok ;工具
package com.springpractice._val; import lombok.val; import java.util.ArrayList; import java.util.HashMap; /** * Hello world! */ public class AppLombok { //不能使用在類的成員變量上,會報編譯錯誤 // val String name; public String test1() { val exampleList = new ArrayList<String>(); exampleList.add("hello world"); val firstElement = exampleList.get(0); final String returnString = firstElement.toLowerCase(); System.out.println(returnString); return returnString; } public void test2() { val map = new HashMap<Integer, String>(); map.put(0, "zero"); map.put(5, "five"); for (val entry : map.entrySet()) { System.out.printf("%d: %s \n", entry.getKey(), entry.getValue()); } } public static void main(String[] args) { final AppLombok app = new AppLombok(); app.test1(); System.out.println("======"); app.test2(); } }
替代本地變量;
package com.springpractice._var; import lombok.var; import java.awt.*; /** * 說明:var的使用 * @author carter * 建立時間: 2019年10月10日 20:08 **/ public class App { public static void main(String[] args) { var x = "Hello"; //編譯報錯,類型是String // x=1; var y = Color.RED; // y=x; //var的類型若是是object ,則不是它的使用場景 var z = new Object(); z = x; System.out.println(x); } }
自動檢查,告別NPE的愛恨情仇。
不使用lombok;
package com.springpractice.nonnull; import lombok.NonNull; import java.util.Objects; /** * 說明:TODO * @author carter * 建立時間: 2019年10月10日 20:16 **/ public class App extends Something{ private String name; public App(Person person){ super("Hello"); if (Objects.isNull(person)){ throw new NullPointerException("person is marked @NonNull but is null"); } this.name = person.getName(); } public static void main(String[] args) { new App(null); } }
使用lombok;
package com.springpractice.nonnull; import lombok.NonNull; /** * 說明:TODO * @author carter * 建立時間: 2019年10月10日 20:20 **/ public class AppLombok extends Something { private String name; public AppLombok(@NonNull Person person){ super("Hello"); this.name = person.getName(); } public static void main(String[] args) { new AppLombok(null); } }
效果同樣:
/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/bin/java -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/lib/tools.jar:/Users/lifesense-szyf01/src/git/github/springbootpractice/lombok-demo/target/classes:/Users/lifesense-szyf01/.m2/repository/org/projectlombok/lombok/1.18.8/lombok-1.18.8.jar com.springpractice.nonnull.AppLombok Exception in thread "main" java.lang.NullPointerException: person is marked non-null but is null at com.springpractice.nonnull.AppLombok.<init>(AppLombok.java:15) at com.springpractice.nonnull.AppLombok.main(AppLombok.java:21) Process finished with exit code 1
代碼路徑: git@github.com:carterbrother/springbootpractice.git/lombok-demo
原創不易,轉載請註明出處。