Python 官方文档:入门教程 => 点击学习
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
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。
声明 String key1="aaa"; key为 key1,value 为map.get(key1);
Map<String,Object> map=new HashMap<>();
map.put("aaa",1);
//获取map的key 和value
//key 为key1
String 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;
public class ColumnUtil {
@FunctionalInterface
public interface SFunction<T, R> extends Function<T, R>, Serializable {
}
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface TableField {
String value() default "";
}
//默认配置
static String defaultSplit = "";
static Integer defaultToType = 0;
public static <T> String getFieldName(SFunction<T, ?> fn) {
return getFieldName(fn, defaultSplit);
}
public static <T> String getFieldName(SFunction<T, ?> fn, String split) {
return getFieldName(fn, split, defaultToType);
}
public static <T> String getFieldName(SFunction<T, ?> 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 <T> SerializedLambda getSerializedLambda(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);
return serializedLambda;
}
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;
}
}
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:
到此这篇关于Java8通过Function获取字段名(获取实体类的字段名称)的文章就介绍到这了,更多相关Java8通过Function获取字段名内容请搜索编程网以前的文章或继续浏览下面的相关文章希望大家以后多多支持编程网!
--结束END--
本文标题: Java8通过Function获取字段名的方法(获取实体类的字段名称)
本文链接: https://www.lsjlt.com/news/137133.html(转载时请注明来源链接)
有问题或投稿请发送至: 邮箱/279061341@qq.com QQ/279061341
下载Word文档到电脑,方便收藏和打印~
2024-03-01
2024-03-01
2024-03-01
2024-02-29
2024-02-29
2024-02-29
2024-02-29
2024-02-29
2024-02-29
2024-02-29
回答
回答
回答
回答
回答
回答
回答
回答
回答
回答
0