java8 function 字段名 Java8通过Function获取字段名的步骤
liangwp 人气:8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
import java.io.Serializable; import java.util.function.Function; /** * 使Function获取序列化能力 */ @FunctionalInterface public interface SFunction<T, R> extends Function<T, R>, Serializable { }
通过SFunction获取字段名
import java.lang.invoke.SerializedLambda; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; public class ColumnUtil { public static <T> String getName(SFunction<T, ?> fn) { // 从function取出序列化方法 Method writeReplaceMethod; try { writeReplaceMethod = fn.getClass().getDeclaredMethod("writeReplace"); } catch (NoSuchMethodException e) { throw new RuntimeException(e); } // 从序列化方法取出序列化的lambda信息 boolean isAccessible = writeReplaceMethod.isAccessible(); writeReplaceMethod.setAccessible(true); SerializedLambda serializedLambda; try { serializedLambda = (SerializedLambda) writeReplaceMethod.invoke(fn); } catch (IllegalAccessException | InvocationTargetException e) { throw new RuntimeException(e); } writeReplaceMethod.setAccessible(isAccessible); // 从lambda信息取出method、field、class等 String fieldName = serializedLambda.getImplMethodName().substring("get".length()); fieldName = fieldName.replaceFirst(fieldName.charAt(0) + "", (fieldName.charAt(0) + "").toLowerCase()); Field field; try { field = Class.forName(serializedLambda.getImplClass().replace("/", ".")).getDeclaredField(fieldName); } catch (ClassNotFoundException | NoSuchFieldException e) { throw new RuntimeException(e); } // 从field取出字段名,可以根据实际情况调整 TableField tableField = field.getAnnotation(TableField.class); if (tableField != null && tableField.value().length() > 0) { return tableField.value(); } else { return fieldName.replaceAll("[A-Z]", "_$0").toLowerCase(); } } }
建一些业务代码进行测试
import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; /** * 字段名注解。测试用 */ @Target(ElementType.FIELD) @Retention(RetentionPolicy.RUNTIME) public @interface TableField { String value() default ""; }
import java.io.Serializable; /** * 用户实体类。测试用 */ public class User implements Serializable { private String loginName; @TableField("nick") private String nickName; public String getLoginName() { return loginName; } public void setLoginName(String loginName) { this.loginName = loginName; } public String getNickName() { return nickName; } public void setNickName(String nickName) { this.nickName = nickName; } }
/** * 测试用 */ public class Test { public static void main(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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