使用 commons-beans BeanUtils 将 JavaBean 转换为具有嵌套名称的键/值映射

Question

我开始使用 BeanUtils 将 Properties 文件转换为 JavaBean。 使用 BeanUtils.populate，我可以很好地做到这一点。但是我可以正确地实现从 JavaBean 到 Map 的复古转换（只存储简单的值）。

根据 BeanUtils 文档中的 Employee Class 查看此示例。

import org.apache.commons.beanutils.BeanUtils;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

public class Employee {

    private Map<String, Address> addressMap = new HashMap<String, Address>();
    private List<Employee> subordinateList = new ArrayList<Employee>();

    private String firstName;
    private String lastName;

    public Address getAddress(String type) {
        if (!addressMap.containsKey(type)) {
            addressMap.put(type, new Address());
        }

        return addressMap.get(type);
    }

    public void setAddress(String type, Address address) {
        addressMap.put(type, address);
    }

    public Employee getSubordinate(int index) {
        if (subordinateList.size() <= index) {
            subordinateList.add(new Employee());
        }

        return subordinateList.get(index);
    }

    public void setSubordinate(int index, Employee subordinate) {
        subordinateList.add(index, subordinate);
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public class Address {
        private String city;
        private String street;
        private int number;

        public String getCity() {
            return city;
        }

        public void setCity(String city) {
            this.city = city;
        }

        public String getStreet() {
            return street;
        }

        public void setStreet(String street) {
            this.street = street;
        }

        public int getNumber() {
            return number;
        }

        public void setNumber(int number) {
            this.number = number;
        }
    }

    public static void main(String[] args) throws Exception {
        Map<String, Object> map = new TreeMap<String, Object>();

        map.put("firstName", "MyfirstName");
        map.put("lastName", "MylastName");
        map.put("address(pro).city", "MyProCity");
        map.put("address(pro).street", "MyProStreet");
        map.put("address(pro).number", 22);

        map.put("subordinate[1].firstName", "Sub1FirstName");
        map.put("subordinate[1].lastName", "Sub1LastName");

        map.put("address(perso).city", "MyPersoCity");
        map.put("address(perso).street", "MyPersoStreet");
        map.put("address(perso).number", 2);

        map.put("subordinate[0].firstName", "Sub0FirstName");
        map.put("subordinate[0].lastName", "Sub0LastName");


        Employee employee = new Employee();
        BeanUtils.populate(employee, map);

        System.out.println(employee.getFirstName());
        System.out.println(employee.getLastName());

        System.out.println(employee.getAddress("pro").city);
        System.out.println(employee.getAddress("pro").street);
        System.out.println(employee.getAddress("pro").number);

        System.out.println(employee.getAddress("perso").city);
        System.out.println(employee.getAddress("perso").street);
        System.out.println(employee.getAddress("perso").number);

        System.out.println(employee.getSubordinate(0).firstName);
        System.out.println(employee.getSubordinate(0).lastName);

        System.out.println(employee.getSubordinate(1).firstName);
        System.out.println(employee.getSubordinate(1).lastName);

        Map<String, Object> map2 = BeanUtils.describe(employee);

        System.out.println("----------------");

        System.out.println(map2);


    }

}

结果：

MyfirstName
MylastName
MyProCity
MyProStreet
22
MyPersoCity
MyPersoStreet
2
Sub0FirstName
Sub0LastName
Sub1FirstName
Sub1LastName
----------------
{lastName=MylastName, class=class Employee, firstName=MyfirstName}

我缺少什么以便 map2 使用 BeanUtils.describe 方法实际存储诸如“address(pro).city”或“subordinate[1].firstName”之类的键？

Answer 1

我终于找到了解决这个问题的方法。首先，我需要根据我当前的 bean 实例检索每个嵌套的 propertyName，并且是递归的。所以我写了一个简单的方法来做到这一点：

import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.beanutils.PropertyUtils;
import org.apache.commons.lang.StringUtils;

import java.beans.PropertyDescriptor;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

public class MyPropertyUtils {

    public List<String> listNestedPropertyName(Object objectSource) throws Exception {
        List<String> nodeNameList = new ArrayList<String>();

        if (Serializable.class.isAssignableFrom(objectSource.getClass())) {
            nodeNameList.add(objectSource.toString());
            return nodeNameList;
        }

        PropertyDescriptor[] propertyDescriptors = PropertyUtils.getPropertyDescriptors(objectSource.getClass());

        for (PropertyDescriptor propertyDescriptor : propertyDescriptors) {

            Method method = propertyDescriptor.getReadMethod();
            if (propertyDescriptor.getReadMethod() == null) {
                continue;
            }

            if (method.getGenericParameterTypes().length > 0) {
                continue;
            }

            String name = propertyDescriptor.getName();

            Object value = method.invoke(objectSource);

            if (value == null) {
                continue;
            }

            if (Map.class.isAssignableFrom(value.getClass())) { // Mapped name
                Map map = ((Map) value);
                name = StringUtils.substringBeforeLast(name, "Map");

                for (Object key : map.keySet()) {
                    String mappedName = name + "(" + key.toString() + ")";
                    List<String> nestedNames = listNestedPropertyName(map.get(key));

                    for (String nestedName : nestedNames) {
                        nodeNameList.add(mappedName + "." + nestedName);
                    }
                }

            } else if (List.class.isAssignableFrom(value.getClass())) { // Indexed name
                List list = ((List) value);
                name = StringUtils.substringBeforeLast(name, "List");

                for (int i = 0; i < list.size(); i++) {
                    String indexedName = name + "[" + i + "]";
                    List<String> nestedNames = listNestedPropertyName(list.get(i));

                    for (String nestedName : nestedNames) {
                        nodeNameList.add(indexedName + "." + nestedName);
                    }
                }
            } else if (Serializable.class.isAssignableFrom(value.getClass())) { // Simple Value
                nodeNameList.add(name);
            } else { // Nested Value
                List<String> nestedNames = listNestedPropertyName(value);

                for (String nestedName : nestedNames) {
                    nodeNameList.add(name + "." + nestedName);
                }
            }
        }

        return nodeNameList;
    }
}

然后我迭代其他这些名称以检索属性值，然后将它们设置在 Map 中。

Map<String, Object> map = new HashMap<String, Object>();

MyPropertyUtils myPropertyUtils = new MyPropertyUtils();
List<String> names = myPropertyUtils.listNestedPropertyName(employee);
for (String name : names) {
    map.put(name, PropertyUtils.getNestedProperty(employee, name));
}

这很适合我的用例。我只是在我的源对象中添加了一个访问器，用于使用常规名称（propertyName + "Map" 或 "List"）访问 Map 或 List。

也许这会让某人感兴趣。无论如何，如果有更明显的事情要做，请告诉我。