Java 反射类型Type用法总结

各个方法

1. 得到class的成员变量

首先得到object的class对象

然后在class对象中用getDeclaredFields()方法来获得class的成员变量

        FieldTest ft = new FieldTest();
        Class ftClass = ft.getClass();

        Field[] fields = ftClass.getDeclaredFields();

2. field的函数

Field对象有很多成员方法

getName()获取名称。

getGenericType() 返回一个Type对象

getType() 返回Class对象

getGenericType 和getType区别:

1. 返回类型一个是Class对象一个是Type接口。

2. 如果属性是泛型，getType（）返回属性的接口类型。getGenericType（）还能返回参数类型。

    String fieldName = field.getName();
    Type genericType = field.getGenericType();
    boolean isParameterizedType = (genericType instanceof ParameterizedType);
    Class fieldClazz = field.getType();
    String valueTypeName = genericType.getTypeName();

3.获取范型的Type和Class

获取 范型的key和value的Type

    Type[] genericTypes = ((ParameterizedType) genericType).getActualTypeArguments();
    Type type0 = genericTypes[0];
    Type type1 = genericTypes[1];

通过google的com.google.common.reflect.TypeToken.of(type1).getRawType()方法获取map的key或者value的class类型。

    Class<?> clazz = com.google.common.reflect.TypeToken.of(type1).getRawType();

总代码

class FieldTest {

    private String pri;
    protected String pro;
    public Map<Integer, HashMap<Integer, Float>> fcmap;


    public FieldTest() {
    }

    public FieldTest(String pri, String pro, String pub) {
        this.pri = pri;
        this.pro = pro;

    }

}

package cn.hyperchain.hvm.abi;


import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class Test {
    private static boolean checkClazzIsSpecific(Class CClazz, Class specific) {
        if (CClazz == specific) return true;
        Class[] interfaces = CClazz.getInterfaces();
        boolean result = false;
        for (Class inter : interfaces) {
            if (result) break;
            if (inter == specific) {
                result = true;
                break;
            }
            result = checkClazzIsSpecific(inter, specific);
        }
        return result;
    }
    public static void main(String args[]) {
        FieldTest ft = new FieldTest();
        Class ftClass = ft.getClass();

        Field[] fields = ftClass.getDeclaredFields();
        for (int i = 0; i < fields.length; i++) {
            Field field = fields[i];
            String fieldName = field.getName();
            Type genericType = field.getGenericType();
            Class fieldClass = field.getClass();
            boolean isParameterizedType = (genericType instanceof ParameterizedType);
            Class fieldClazz = field.getType();
            String valueTypeName = genericType.getTypeName();

            System.out.println();
            System.out.println("-------------------------------------------------");
            System.out.println();
            System.out.println("fieldName: " + fieldName);
            System.out.println("genericType: " + genericType);
                   System.out.println("fieldClazz: " + fieldClazz);
            System.out.println("isParameterizedType: " + isParameterizedType);
            System.out.println("valueTypeName: " + valueTypeName);
            if (checkClazzIsSpecific(fieldClazz, Map.class)) {
                Type[] genericTypes = ((ParameterizedType) genericType).getActualTypeArguments();
                Type type0 = genericTypes[0];
                Type type1 = genericTypes[1];
                String type1Name = genericTypes[1].getTypeName();
                System.out.println("type0: " + type0);
                System.out.println("type1: " + type1);
                System.out.println("type1Name: " + type1Name);
                System.out.println(type1 instanceof ParameterizedType);
                Type type3 = ((ParameterizedType)type1).getOwnerType();
                Class type4 = type1.getClass();
                //Class<?> type5 = (Class<?>) type1;
                System.out.println("type3: " + type3);
                System.out.println("type4: " + type4);
                //System.out.println(type5);
                Class<?> clazz = com.google.common.reflect.TypeToken.of(type1).getRawType();
                System.out.println("clazz: " + clazz);
            }
        }
    }
}
class FieldTest {

    private String pri;
    protected String pro;
//    public Map<String, Integer> map;
    public Map<Integer, HashMap<Integer, Float>> fcmap;


    public FieldTest() {
    }

    public FieldTest(String pri, String pro, String pub) {
        this.pri = pri;
        this.pro = pro;

    }

}
class abc {

    private String pri;
    protected String pro;
    public String pub;
    public String[] string;
    public int[] innt;
    public Map<String, Integer> map;


    public abc() {
    }

    public abc(String pri, String pro, String pub) {
        this.pri = pri;
        this.pro = pro;
        this.pub = pub;
    }

}

结果：

-------------------------------------------------

fieldName: pri
genericType: class java.lang.String
fieldClazz: class java.lang.String
isParameterizedType: false
valueTypeName: java.lang.String

-------------------------------------------------

fieldName: pro
genericType: class java.lang.String
fieldClazz: class java.lang.String
isParameterizedType: false
valueTypeName: java.lang.String

-------------------------------------------------

fieldName: fcmap
genericType: java.util.Map<java.lang.Integer, java.util.HashMap<java.lang.Integer, java.lang.Float>>
fieldClazz: interface java.util.Map
isParameterizedType: true
valueTypeName: java.util.Map<java.lang.Integer, java.util.HashMap<java.lang.Integer, java.lang.Float>>
type0: class java.lang.Integer
type1: java.util.HashMap<java.lang.Integer, java.lang.Float>
type1Name: java.util.HashMap<java.lang.Integer, java.lang.Float>
true
type3: null
type4: class sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl
clazz: class java.util.HashMap

Process finished with exit code 0