Java8通过Function获取字段名的方法(获取实体类的字段名称) Java8通过Function获取字段名的方

看似很鸡肋其实在某些特殊场景还是比较有用的。
比如你将实体类转Map或者拿到一个Map结果的时候，你是怎么获取某个map的key和value。
方法一：声明 String key1="aaa"; key为 key1,value 为map.get(key1);

Map map=new HashMap<>(); map.put("aaa",1); //获取map的key 和value//key 为key1String key1="aaa"; //value 为 map.get(key1)map.get(key1);

然后好像日常使用中也没有其他的方法了，下面将带来另外一种使用方法，话不多说直接上代码[/code]

import java.io.Serializable; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import java.lang.invoke.SerializedLambda; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.function.Function; /** * Java8通过Function函数获取字段名称(获取实体类的字段名称) * @see ColumnUtil#main(java.lang.String[]) 使用示例 * @author jx */public class ColumnUtil {/*** 使Function获取序列化能力*/@FunctionalInterfacepublic interface SFunction extends Function, Serializable {}/*** 字段名注解,声明表字段*/@Target(ElementType.FIELD)@Retention(RetentionPolicy.RUNTIME)public @interface TableField {String value() default ""; }//默认配置static String defaultSplit = ""; static Integer defaultToType = 0; /*** 获取实体类的字段名称(实体声明的字段名称)*/public static String getFieldName(SFunction fn) {return getFieldName(fn, defaultSplit); }/*** 获取实体类的字段名称* @param split 分隔符，多个字母自定义分隔符*/public static String getFieldName(SFunction fn, String split) {return getFieldName(fn, split, defaultToType); }/*** 获取实体类的字段名称* @param split 分隔符，多个字母自定义分隔符* @param toType 转换方式，多个字母以大小写方式返回 0.不做转换 1.大写 2.小写*/public static String getFieldName(SFunction fn, String split, Integer toType) {SerializedLambda serializedLambda = getSerializedLambda(fn); // 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 {//0.不做转换 1.大写 2.小写switch (toType) {case 1:return fieldName.replaceAll("[A-Z]", split + "$0").toUpperCase(); case 2:return fieldName.replaceAll("[A-Z]", split + "$0").toLowerCase(); default:return fieldName.replaceAll("[A-Z]", split + "$0"); }}}private static SerializedLambda getSerializedLambda(SFunction 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); return serializedLambda; }/*** 测试用户实体类*/public static class TestUserDemo implements Serializable {private static final long serialVersionUID = 1L; private String loginName; private String name; private String companySimpleName; @ColumnUtil.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; }public static long getSerialVersionUID() {return serialVersionUID; }public String getName() {return name; }public void setName(String name) {this.name = name; }public String getCompanySimpleName() {return companySimpleName; }public void setCompanySimpleName(String companySimpleName) {this.companySimpleName = companySimpleName; }}/*** 参考示例*/public static void main(String[] args) {//实体类原字段名称返回System.out.println(); System.out.println("实体类原字段名称返回"); System.out.println("字段名：" + ColumnUtil.getFieldName(TestUserDemo::getLoginName)); System.out.println("字段名：" + ColumnUtil.getFieldName(TestUserDemo::getNickName)); System.out.println("字段名：" + ColumnUtil.getFieldName(TestUserDemo::getCompanySimpleName)); System.out.println(); System.out.println("实体类字段名称增加分隔符"); System.out.println("字段名：" + ColumnUtil.getFieldName(TestUserDemo::getCompanySimpleName, "_")); System.out.println(); System.out.println("实体类字段名称增加分隔符 + 大小写"); System.out.println("字段名：" + ColumnUtil.getFieldName(TestUserDemo::getCompanySimpleName, "_", 0)); System.out.println("字段名：" + ColumnUtil.getFieldName(TestUserDemo::getCompanySimpleName, "_", 1)); System.out.println("字段名：" + ColumnUtil.getFieldName(TestUserDemo::getCompanySimpleName, "_", 2)); }}

输出结果：

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