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
