【转载】java通过反射获取类名、属性名称以及@注解信息
前言: 场景为Spring data jpa,想通过反射获取表名以及id做点事情。那么如何通过反射进行呢。
这里转载了一篇比较好的文章。
getFields():获得某个类的所有的公共(public)的字段,包括父类中的字段。
getDeclaredFields():获得某个类的所有声明的字段,即包括public、private和proteced,但是不包括父类的声明字段。
Spring data jpa依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
反射工具类:JPA之@Entity、@Table、@Column、@Id
模仿mybatisplus的TableField接口,写的ColumnConf。可以用户前端页面表头或Excel导出表头等
package net.test.common.annotation;
import java.lang.annotation.*;
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD})
public @interface ColumnConf {
String value() default "";
}
import net.test.common.annotation.ColumnConf
public class UserListVO {
/**
* 客户名称
*/
@ColumnConf("客户名称")
private String clientName;
}
import net.test.common.annotation.ColumnConf;
import javax.persistence.Column;
import javax.persistence.Id;
import javax.persistence.Table;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
public class ReflectUtils {
public static final String TABLE_NAME = "tableName";
public static final String CLASS_NAME = "className";
public static final String FIELD_NAME = "fieldNames";
public static final String COLUMN_NAME = "column";
/**
* * 获取属性名数组
*
* @param clazz
* @return
*/
public static String[] getPropertiesName(Class<?> clazz) {
Field[] fields = clazz.getDeclaredFields();
String[] fieldNameStrings = new String[fields.length];
for (int i = 0; i < fieldNameStrings.length; i++) {
fieldNameStrings[i] = fields[i].getName();
}
return fieldNameStrings;
}
/**
* 通过反射设置属性的值
*
* @param fieldName 属性名
* @param fieldValue 属性值
* @param object 实体类对象
* @param parameterTypes 设置属性值的类型 String.class
* @throws
*/
public static void setPropertyValue(String fieldName, Object fieldValue, Object object, Class<?>... parameterTypes) {
try {
Field[] fields = object.getClass().getDeclaredFields();
for (int i = 0; i < fields.length; i++) {
Field field = fields[i];
//字段名称
String name = field.getName();
if (name.equals(fieldName)) {
field.setAccessible(true);
//field.set(object,fieldValue); //可代替下面的拼接set方法;
//将属性的首字符大写,方便构造get,set方法
String methname = name.substring(0, 1).toUpperCase() + name.substring(1);
Method m = object.getClass().getMethod("set" + methname, parameterTypes);
m.invoke(object, fieldValue);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 根据主键名称获取实体类主键属性值
*
* @param clazz 实体类对象
* @param fieldName 属性名
* @return
*/
public static Object getPropertyValue(Object clazz, String fieldName) {
try {
/** 方法一
Field field = clazz.getClass().getDeclaredField(fieldName);
//设置对象的访问权限,保证对private的属性的访问
field.setAccessible(true);
Object value = field.get(clazz);
*/
String firstLetter = fieldName.substring(0, 1).toUpperCase();
String getter = "get" + firstLetter + fieldName.substring(1);
Method method = clazz.getClass().getMethod(getter, new Class[]{});
Object value = method.invoke(clazz, new Object[]{});
return value;
} catch (Exception e) {
return null;
}
}
/**
* 通过反射将 source不为空的值赋值给target
*
* @param source 实体类对象
* @param target 实体类对象
* @throws Exception
*/
public static void copyProperties(Object source, Object target) throws Exception {
Field[] field = source.getClass().getDeclaredFields();
for (int i = 0; i < field.length; i++) {
String name = field[i].getName();
if ("serialVersionUID".equals(name)) {
continue;
}
name = name.substring(0, 1).toUpperCase() + name.substring(1);
Method m1 = source.getClass().getMethod("get" + name);
Object value = m1.invoke(source);
if (value != null) {
Field f = field[i];
//设置对象的访问权限,保证对private的属性的访问
f.setAccessible(true);
f.set(target, value);
}
}
}
/**
* 获取实体类主键
*
* @param clazz
* @return
*/
public static Field getJpaIdField(Class<?> clazz) {
Field[] fields = clazz.getDeclaredFields();
Field item = null;
for (Field field : fields) {
Id id = field.getAnnotation(Id.class);
if (id != null) {
field.setAccessible(true);
item = field;
break;
}
}
if (item == null) {
Class<?> superclass = clazz.getSuperclass();
if (superclass != null) {
item = getJpaIdField(superclass);
}
}
return item;
}
/**
* 获取实体类 @Column 的其中一个属性名称
*
* @param clazz
* @return
*/
public static Map<String, String> getJpaColumns(Class<?> clazz) {
Map<String, String> map = new ConcurrentHashMap<>();
Field[] fields = clazz.getDeclaredFields();
for (Field field : fields) {
if (field.isAnnotationPresent(Column.class)) {
Column declaredAnnotation = field.getDeclaredAnnotation(Column.class);
String column = declaredAnnotation.name();
map.put(FIELD_NAME, field.getName());
map.put(COLUMN_NAME, column);
}
}
return map;
}
/**
* 通过获取类上的@Table注解获取表名称
*
* @param clazz
* @return
*/
public static Map<String, String> getJpaTableName(Class<?> clazz) {
Map<String, String> map = new ConcurrentHashMap<>();
Table annotation = clazz.getAnnotation(Table.class);
String name = annotation.name();
String className = clazz.getSimpleName();
map.put(TABLE_NAME, name);
map.put(CLASS_NAME, className);
return map;
}
/**
* 获取VO @ColumnConf注解 属性与中文名称
*
* @param clazz
* @return
*/
public static Map<String, String> getVoColumns(Class<?> clazz) {
Map<String, String> map = new ConcurrentHashMap<>();
Field[] fields = clazz.getDeclaredFields();
for (Field field : fields) {
ColumnConf cc = field.getAnnotation(ColumnConf.class);
if (cc == null) {
continue;
}
map.put("code", field.getName());
map.put("title", cc.value());
}
return map;
}
public static void main(String[] args) {
Student s = new Student("张三", 23);
System.out.println(s); //student [name=张三, age=23]
setPropertyValue("name", "李四", s, String.class);
System.out.println(s); //student [name=李四, age=23]
Object val = getPropertyValue("name", s);
System.out.println(val); //李四
String[] strArray = getPropertiesName(Student.class);
for (int i = 0; i < strArray.length; i++) {
System.out.println(strArray[i]);
}
}
}
版权声明:本文为CSDN博主「航空母舰」的原创文章,遵循CC 4.0 BY-SA版权协议,转载请附上原文出处链接及本声明。
原文链接:https://blog.csdn.net/hudeyong926/article/details/116236958