How to use reflection to obtain generic information in java

ParameterizedType means parameterized type.

Explanation:

Anything with "" in the declared type is a parameterized type, such as List<integer></integer>, Map<string></string>.

getActualTypeArguments()Return Type[], which is the parameters in "", such as Map<string></string>.

getRawType() Return to Tpye and get the type in front of "", such as List<string></string>.

getOwnerType() Returns Type. When calling a variable of type O.I, O will be returned, such as Map.Entry<long> </long>.

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Example code:

import org.junit.Test;
import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.math.BigDecimal;
import java.util.Map;
public class ReflectDemo {
    private static Map<String, BigDecimal>map;
    @Test
    public void test(){
        try {
            Class<?> aClass = Class.forName("com.test.annotation.param.ReflectDemo");
            //获取map属性对象
            Field field = aClass.getDeclaredField("map");
            //获取map属性的类型
            Type type = field.getGenericType();//返回属性声明的Type类型
            if (type instanceof ParameterizedType) {
                //强转为ParameterizedType对象
                ParameterizedType parameterizedType = (ParameterizedType) type;
                //获取原始类型
                Type rawType = parameterizedType.getRawType();
                System.out.println("map的原始类型为："+rawType);
                //获取map的类型的所有泛型信息
                Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
                for(int i=0;i<actualTypeArguments.length;i++){
                    System.out.println("Map类型的第"+(i+1)+"个泛型为："+actualTypeArguments[i]);
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Running result:

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