我有一个POJO,以及一个(目前尚未构建的)类,该类将返回POJO的列表。我希望自动生成访问POJO作为Map所需的代码。这是个好主意吗?是否可以自动完成,并且我需要为想要以此方式处理的每个POJO手动执行此操作?
谢谢, Andy
谢谢, Andy
你可以使用Commons BeanUtils的BeanMap
来实现这个功能。
Map map = new BeanMap(someBean);
更新:由于Android中存在某些库依赖问题,所以这不是一种选项,因此这里提供一个基本示例,介绍如何使用反射API进行操作:
public static Map<String, Object> mapProperties(Object bean) throws Exception {
Map<String, Object> properties = new HashMap<>();
for (Method method : bean.getClass().getDeclaredMethods()) {
if (Modifier.isPublic(method.getModifiers())
&& method.getParameterTypes().length == 0
&& method.getReturnType() != void.class
&& method.getName().matches("^(get|is).+")
) {
String name = method.getName().replaceAll("^(get|is)", "");
name = Character.toLowerCase(name.charAt(0)) + (name.length() > 1 ? name.substring(1) : "");
Object value = method.invoke(bean);
properties.put(name, value);
}
}
return properties;
}
如果能够使用java.beans
API,那么你只需要执行以下操作:public static Map<String, Object> mapProperties(Object bean) throws Exception {
Map<String, Object> properties = new HashMap<>();
for (PropertyDescriptor property : Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors()) {
String name = property.getName();
Object value = property.getReadMethod().invoke(bean);
properties.put(name, value);
}
return properties;
}
import java.beans.*; // Or, import com.googlecode.openbeans.*
import java.util.*;
public class BeanMap extends AbstractMap<String, Object> {
private static final Object[] NO_ARGS = new Object[] {};
private HashMap<String, PropertyDescriptor> properties;
private Object bean;
public BeanMap(Object bean) throws IntrospectionException {
this.bean = bean;
properties = new HashMap<String, PropertyDescriptor>();
BeanInfo info = Introspector.getBeanInfo(bean.getClass());
for(PropertyDescriptor property : info.getPropertyDescriptors()) {
properties.put(property.getName(), property);
}
}
@Override public Object get(Object key) {
PropertyDescriptor property = properties.get(key);
if(property == null)
return null;
try {
return property.getReadMethod().invoke(bean, NO_ARGS);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
@Override public Object put(String key, Object value) {
PropertyDescriptor property = properties.get(key);
try {
return property.getWriteMethod().invoke(bean, new Object[] {value});
} catch (Exception e) {
throw new RuntimeException(e);
}
}
@Override public Set<Map.Entry<String, Object>> entrySet() {
HashSet<Map.Entry<String, Object>> result = new HashSet<Map.Entry<String, Object>>(properties.size() * 2);
for(PropertyDescriptor property : properties.values()) {
String key = property.getName();
Object value;
try {
value = property.getReadMethod().invoke(bean, NO_ARGS);
} catch (Exception e) {
throw new RuntimeException(e);
}
result.add(new PropertyEntry(key, value));
}
return Collections.unmodifiableSet(result);
}
@Override public int size() { return properties.size(); }
@Override public boolean containsKey(Object key) {
return properties.containsKey(key);
}
class PropertyEntry extends AbstractMap.SimpleEntry<String, Object> {
PropertyEntry(String key, Object value) {
super(key, value);
}
@Override public Object setValue(Object value) {
super.setValue(value);
return BeanMap.this.put(getKey(), value);
}
}
}