ToStringBuilder如何忽略null和空字符串

日常开发中，经常用org.apache.commons.lang3.builder.ToStringBuilder工具类来记录日志，比如：

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package com.cnblogs.yjmyzz;   import org.apache.commons.lang3.builder.ToStringBuilder; import org.apache.commons.lang3.builder.ToStringStyle;   import java.util.Date;   /**  * @author 菩提树下的杨过  * @className ToStringTest  * @description TODO  * @date 2022/5/8 07:24  */ public class ToStringTest {         static class DemoObject {         private String a;         private String b = "";         private String c = "abc";         private Date d = new Date();         private Integer e;     }           public static void main(String[] args) {         DemoObject obj = new DemoObject();         //原始toString()         System.out.println(obj);                   //ToStringBuilder的输出(默认风格）         System.out.println(ToStringBuilder.reflectionToString(obj));                   //ToStringBuilder的输出(短前缀风格）         System.out.println(ToStringBuilder.reflectionToString(obj, ToStringStyle.SHORT_PREFIX_STYLE));     } }

输出如下：

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com.cnblogs.yjmyzz.ToStringTest$DemoObject@1786dec2 com.cnblogs.yjmyzz.ToStringTest$DemoObject@1786dec2[a=<null>,b=,c=abc,d=Sun May 08 07:35:50 CST 2022,e=<null>] ToStringTest.DemoObject[a=<null>,b=,c=abc,d=Sun May 08 07:35:50 CST 2022,e=<null>]

从结果上看：

行1：也就是Object默认的toString()输出，只有类名以及对象实例的hashCode，内部成员信息完全看不出来

行2：使用ToStringBuilder工具类输出对象信息，包含了几乎所有完整信息

行3：如果觉得行2的输出，类名太长，可以指定短前缀风格

 

但是不管是行2还是行3的风格，当field值为null或字符串时，仍然会输出，如果想把这些空值给过滤掉，可以参考下面的方法，加一个类：

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package com.cnblogs.yjmyzz;   import org.apache.commons.lang3.builder.ReflectionToStringBuilder; import org.apache.commons.lang3.builder.ToStringBuilder; import org.apache.commons.lang3.builder.ToStringStyle;   import java.lang.reflect.Field; import java.util.Date;   /**  * @author 菩提树下的杨过  * @className ToStringTest  * @description TODO  * @date 2022/5/8 07:24  */ public class ToStringTest {         static class DemoObject {         private String a;         private String b = "";         private String c = "abc";         private Date d = new Date();         private Integer e;     }       /**      * 新增的工具类      */     static class ToStringUtil {         public static String toStringWithAttributes(Object ofInterest, ToStringStyle style) {             ReflectionToStringBuilder builder = new ReflectionToStringBuilder(ofInterest, style) {                 @Override                 protected boolean accept(Field field) {                     try {                         Object value = field.get(ofInterest);                         return super.accept(field) && value != null && !"".equalsIgnoreCase(value.toString());                     } catch (IllegalAccessException e) {                         return super.accept(field);                     }                 }             };             return builder.toString();         }     }       public static void main(String[] args) {         DemoObject obj = new DemoObject();         //原始toString()         System.out.println(obj);           //去掉null和空字符串的输出         System.out.println(ToStringUtil.toStringWithAttributes(obj, ToStringStyle.SHORT_PREFIX_STYLE));       } }

再次运行：

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1 2	com.cnblogs.yjmyzz.ToStringTest$DemoObject@1786dec2 ToStringTest.DemoObject[c=abc,d=Sun May 08 07:43:01 CST 2022]

从输出上看，null值以及空字符串都被成功过滤掉了