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lombok 简化java代码注解

lombok 简化 java 代码注解

安装 lombok 插件

以 intellij ide 为例

File-->Setting-->Plugins--> 搜索“lombok plugin”，安装后重启 ide

lombok 注解

lombok 提供的注解不多，可以参考官方视频的讲解和官方文档。

Lombok 注解在线帮助文档：https://projectlombok.org/features/index.html

下面介绍几个我常用的 lombok 注解：

  • @Data ：注解在类上；提供类所有属性的 getting 和 setting 方法，此外还提供了equals、canEqual、hashCode、toString 方法
  • @Setter：注解在属性上；为属性提供 setting 方法
  • @Getter：注解在属性上；为属性提供 getting 方法
  • @Log4j ：注解在类上；为类提供一个 属性名为 log 的 log4j 日志对象
  • @NoArgsConstructor：注解在类上；为类提供一个无参的构造方法
  • @AllArgsConstructor：注解在类上；为类提供一个全参的构造方法
  • @NonNull：注解在参数上，可以省略重复的 if( null == persion)这类异常处理
  • @Cleanup：注解在输入输出流等需要释放资源的变量上，不需要写额外繁琐而重复的释放资源代码

不使用lombok

import java.io.*;

public class CleanupExample {
public static void main(String[] args) throws IOException {
InputStream in = new FileInputStream(args[0]);
try {
OutputStream out = new FileOutputStream(args[1]);
try {
byte[] b = new byte[10000];
while (true) {
int r = in.read(b);
if (r == -1) break;
out.write(b, 0, r);
}
} finally {
if (out != null) {
out.close();
}
}
} finally {
if (in != null) {
in.close();
}
}
}
}

使用lombok

import lombok.Cleanup;
import java.io.*;

public class CleanupExample {
public static void main(String[] args) throws IOException {
@Cleanup InputStream in = new FileInputStream(args[0]);
@Cleanup OutputStream out = new FileOutputStream(args[1]);
byte[] b = new byte[10000];
while (true) {
int r = in.read(b);
if (r == -1) break;
out.write(b, 0, r);
}
}
}

  • val：最终局部变量，在迭代器循环时刻做简单缩写。

不使用lombok

public void example2() {
  final HashMap<Integer, String> map = new HashMap<Integer, String>();
  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());
  }
}

使用lombok

public void example2() {
 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());
 }
}

下面是简单示例

不使用 lombok 的方案

public class Person {
    private String id;
    private String name;
    private String identity;
    private Logger log = Logger.getLogger(Person.class);
    public Person() {

}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">Person</span>(<span class="hljs-title class_">String</span> id, <span class="hljs-title class_">String</span> name, <span class="hljs-title class_">String</span> identity) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">id</span>              = id;
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">name</span>       = name;
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">identity</span>  = identity;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">getId</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> id;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">getName</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> name;
}

<span class="hljs-keyword">public</span> <span class="hljs-title class_">String</span> <span class="hljs-title function_">getIdentity</span>(<span class="hljs-params"></span>) {
    <span class="hljs-keyword">return</span> identity;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setId</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> id</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">id</span> = id;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setName</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> name</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">name</span> = name;
}

<span class="hljs-keyword">public</span> <span class="hljs-built_in">void</span> <span class="hljs-title function_">setIdentity</span>(<span class="hljs-params"><span class="hljs-built_in">String</span> identity</span>) {
    <span class="hljs-variable language_">this</span>.<span class="hljs-property">identity</span> = identity;
}



}

使用 lombok 的方案

@Data
@Log4j
@NoArgsConstructor
@AllArgsConstructor
public class Person {

<span class="hljs-selector-tag">private</span> <span class="hljs-selector-tag">String</span> <span class="hljs-selector-tag">id</span>;
<span class="hljs-selector-tag">private</span> <span class="hljs-selector-tag">String</span> <span class="hljs-selector-tag">name</span>;
<span class="hljs-selector-tag">private</span> <span class="hljs-selector-tag">String</span> <span class="hljs-selector-tag">identity</span>;



}

参考文档：