最近在项目中操作MongoDB数据库查找数据时,出现查找返回的结果是Java实体类entity,之前的解决办法是利用new Gson().toJson(datalist)
,转为String字符串,但是,转化的结果为:[{SNAME=1111, BODY_ID=genitals, id=5e80dddc57cd4c667c0047ad, BODY_NAME=222, SID=hip01}]
且为String类型,这样就取不到list中想要的数据了。
在Java程序中创建的是JavaBean,mongodb返回的结果为javabean形式,可以采用Bean转Map将结果转化为一个map集合。
public class BeanMapUtil {
/**
* 将对象装换为map
*
* @param bean
* @return
*/
public static <T> Map<String, Object> beanToMap(T bean) {
Map<String, Object> map = new HashMap<>();
if (bean != null) {
BeanMap beanMap = BeanMap.create(bean);
for (Object key : beanMap.keySet()) {
map.put(String.valueOf(key), beanMap.get(key));
}
}
return map;
}
/**
* 将map装换为javabean对象
*
* @param map
* @param bean
* @return
*/
public static <T> T mapToBean(Map<String, Object> map, T bean) {
BeanMap beanMap = BeanMap.create(bean);
beanMap.putAll(map);
return bean;
}
/**
* 将List<T>转换为List<Map<String, Object>>
*
* @param objList
* @return
*/
public static <T> List<Map<String, Object>> beansToMaps(List<T> objList) {
List<Map<String, Object>> list = Collections.emptyList();
if (objList != null && objList.size() > 0) {
list = new ArrayList<>(objList.size());
Map<String, Object> map;
T bean;
for (int i = 0, size = objList.size(); i < size; i++) {
bean = objList.get(i);
map = beanToMap(bean);
list.add(map);
}
}
return list;
}
/**
* 将List<Map<String,Object>>转换为List<T>
*
* @param maps
* @param clazz
* @return
* @throws InstantiationException
* @throws IllegalAccessException
*/
public static <T> List<T> mapsToBeans(List<Map<String, Object>> maps, Class<T> clazz) {
List<T> list = Collections.emptyList();
if (maps != null && maps.size() > 0) {
list = new ArrayList<>(maps.size());
Map<String, Object> map;
T bean;
try {
for (int i = 0, size = maps.size(); i < size; i++) {
map = maps.get(i);
bean = mapToBean(map, clazz.getDeclaredConstructor().newInstance());
list.add(bean);
}
} catch (IllegalAccessException ex) {
ex.printStackTrace();
} catch (NoSuchMethodException ex) {
ex.printStackTrace();
} catch (InvocationTargetException ex) {
ex.printStackTrace();
} catch (InstantiationException ex) {
ex.printStackTrace();
}
}
return list;
}
输出的结果为list< Map<String,Object> >
形式,就可以按照常规的List去取到map集合中的元素了。