Java8通过Function获取字段名的步骤
摘要:Java8通过Function获取字段名,解决硬编码,效果类似于mybatis-plus的LambdaQueryWrapper。
本文总共三个步骤:
1、使Function获取序列化能力;
2、通过SFunction获取字段名;
3、建一些业务代码进行测试;
使Function获取序列化能力
importjava.io.Serializable; importjava.util.function.Function; /** *使Function获取序列化能力 */ @FunctionalInterface publicinterfaceSFunctionextendsFunction ,Serializable{ }
通过SFunction获取字段名
importjava.lang.invoke.SerializedLambda; importjava.lang.reflect.Field; importjava.lang.reflect.InvocationTargetException; importjava.lang.reflect.Method; publicclassColumnUtil{ publicstaticStringgetName(SFunction fn){ //从function取出序列化方法 MethodwriteReplaceMethod; try{ writeReplaceMethod=fn.getClass().getDeclaredMethod("writeReplace"); }catch(NoSuchMethodExceptione){ thrownewRuntimeException(e); } //从序列化方法取出序列化的lambda信息 booleanisAccessible=writeReplaceMethod.isAccessible(); writeReplaceMethod.setAccessible(true); SerializedLambdaserializedLambda; try{ serializedLambda=(SerializedLambda)writeReplaceMethod.invoke(fn); }catch(IllegalAccessException|InvocationTargetExceptione){ thrownewRuntimeException(e); } writeReplaceMethod.setAccessible(isAccessible); //从lambda信息取出method、field、class等 StringfieldName=serializedLambda.getImplMethodName().substring("get".length()); fieldName=fieldName.replaceFirst(fieldName.charAt(0)+"",(fieldName.charAt(0)+"").toLowerCase()); Fieldfield; try{ field=Class.forName(serializedLambda.getImplClass().replace("/",".")).getDeclaredField(fieldName); }catch(ClassNotFoundException|NoSuchFieldExceptione){ thrownewRuntimeException(e); } //从field取出字段名,可以根据实际情况调整 TableFieldtableField=field.getAnnotation(TableField.class); if(tableField!=null&&tableField.value().length()>0){ returntableField.value(); }else{ returnfieldName.replaceAll("[A-Z]","_$0").toLowerCase(); } } }
建一些业务代码进行测试
importjava.lang.annotation.ElementType; importjava.lang.annotation.Retention; importjava.lang.annotation.RetentionPolicy; importjava.lang.annotation.Target; /** *字段名注解。测试用 */ @Target(ElementType.FIELD) @Retention(RetentionPolicy.RUNTIME) public@interfaceTableField{ Stringvalue()default""; }
importjava.io.Serializable; /** *用户实体类。测试用 */ publicclassUserimplementsSerializable{ privateStringloginName; @TableField("nick") privateStringnickName; publicStringgetLoginName(){ returnloginName; } publicvoidsetLoginName(StringloginName){ this.loginName=loginName; } publicStringgetNickName(){ returnnickName; } publicvoidsetNickName(StringnickName){ this.nickName=nickName; } }
/** *测试用 */ publicclassTest{ publicstaticvoidmain(String[]args){ System.out.println("字段名:"+ColumnUtil.getName(User::getLoginName)); System.out.println("字段名:"+ColumnUtil.getName(User::getNickName)); } }
运行结果:
字段名:login_name
字段名:nick
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