Java反射获取所有私有字段

Question

我想知道有没有办法在java及其类型中获取某些类的所有私有字段.

例如,假设我有一个班级

class SomeClass {
    private String aaa;
    private SomeOtherClass bbb;
    private double ccc;
}

现在,我想获得的所有私有字段(aaa,bbb,ccc类)SomeClass(如果不知道前期所有字段的名称),并检查它们的类型.

Answer 1

有可能获得与方法的所有字段getDeclaredFields()的Class.然后你必须检查每个字段的修饰符以找到私有的:

List<Field> privateFields = new ArrayList<>();
Field[] allFields = SomeClass.class.getDeclaredFields();
for (Field field : allFields) {
    if (Modifier.isPrivate(field.getModifiers())) {
        privateFields.add(field);
    }
}

请注意,getDeclaredFields()不会返回继承的字段.

最终,您将使用方法Field.getType()获取字段的类型.

Answer 2

您可以使用它Modifier来确定某个字段是否为私有字段.请务必使用该getDeclaredFields方法确保从类中检索私有字段,调用getFields将仅返回公共字段.

public class SomeClass {

    private String aaa;
    private Date date;
    private double ccc;
    public int notPrivate;

    public static void main(String[] args) {
        List<Field> fields = getPrivateFields(SomeClass.class);
        for(Field field: fields){
            System.out.println(field.getName());
        }
    }

    public static List<Field> getPrivateFields(Class<?> theClass){
        List<Field> privateFields = new ArrayList<Field>();

        Field[] fields = theClass.getDeclaredFields();

        for(Field field:fields){
            if(Modifier.isPrivate(field.getModifiers())){
                privateFields.add(field);
            }
        }
        return privateFields;
    }
}

Answer 3

试试FieldUtilsapache commons-lang3:

FieldUtils.getAllFieldsList(Class<?> cls)

Answer 4

使用Java 8:

Field[] fields = String.class.getDeclaredFields();
List<Field> privateFieldList = Arrays.asList(fields).stream().filter(field -> Modifier.isPrivate(field.getModifiers())).collect(
        Collectors.toList());

Answer 5

检查Field是否为私有

您可以使用Modifier.isPrivate 过滤字段:

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
// ...
Field field = null;
// retrieve the field in some way
// ...
Modifier.isPrivate(field.getModifiers())

在单个Field对象上,true如果该字段是返回private

收集班级的所有领域

要收集所有字段使用:

1)如果只需要类的字段而没有从类层次结构中获取的字段,则可以使用:

Field[] fields = SomeClass.class.getDeclaredFields();

2)如果您不想重新发明轮子并获得类层次结构的所有字段,您可以依赖Apache Commons Lang版本3.2+,它提供FieldUtils.getAllFieldsList:

import java.lang.reflect.Field;
import java.util.AbstractCollection;
import java.util.AbstractList;
import java.util.AbstractSequentialList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

import org.apache.commons.lang3.reflect.FieldUtils;
import org.junit.Assert;
import org.junit.Test;

public class FieldUtilsTest {

    @Test
    public void testGetAllFieldsList() {

        // Get all fields in this class and all of its parents
        final List<Field> allFields = FieldUtils.getAllFieldsList(LinkedList.class);

        // Get the fields form each individual class in the type's hierarchy
        final List<Field> allFieldsClass = Arrays.asList(LinkedList.class.getFields());
        final List<Field> allFieldsParent = Arrays.asList(AbstractSequentialList.class.getFields());
        final List<Field> allFieldsParentsParent = Arrays.asList(AbstractList.class.getFields());
        final List<Field> allFieldsParentsParentsParent = Arrays.asList(AbstractCollection.class.getFields());

        // Test that `getAllFieldsList` did truly get all of the fields of the the class and all its parents 
        Assert.assertTrue(allFields.containsAll(allFieldsClass));
        Assert.assertTrue(allFields.containsAll(allFieldsParent));
        Assert.assertTrue(allFields.containsAll(allFieldsParentsParent));
        Assert.assertTrue(allFields.containsAll(allFieldsParentsParentsParent));
    }
}

Answer 6

你的意思是喜欢

Field[] fields = SomeClass.class.getDeclaredFields();