从 MongoDB 检索值时将 DBObject 转换为 Java 对象
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Converting DBObject to Java Object while retrieve values from MongoDB
提问by It's me
From my Java application, I have stored the values in mongoDB in ArrayList(set of Java objects). How can I retrieve the data from DBObject
在我的 Java 应用程序中，我已将 mongoDB 中的值存储在 ArrayList（Java 对象集）中。如何从 DBObject 检索数据
I am storing the data in mongoDB like this:
我将数据存储在 mongoDB 中，如下所示：
{ "students" : [{"firstName" : "Jesse", "lastName" : "Varnell", "age" : "15", "gender" : "M" }, { "firstName" : "John", "lastName" : "Doe", "age" : "13", "gender" : "F"}] }
I am having the Java Object for the Student like:
我有学生的 Java 对象，例如：
public class Student {
public String firstName;
public String lastName;
public String age;
public String gender; // M, F
}
I am retrieving the data from mongoDB like:
我正在从 mongoDB 中检索数据，例如：
BasicDBObject query = new BasicDBObject();
query.put("user", username);
DBCursor cursor = theCollection.find(query);
while (cursor.hasNext()) {
DBObject theObj = cursor.next();
//How to get the DBObject value to ArrayList of Java Object?
}
采纳答案by Parvin Gasimzade
You can do it as follows :
你可以这样做：
List<Student> students = new ArrayList<Student>();
BasicDBObject query = new BasicDBObject();
query.put("user", username);
DBCursor cursor = theCollection.find(query);
while (cursor.hasNext()) {
DBObject theObj = cursor.next();
//How to get the DBObject value to ArrayList of Java Object?
BasicDBList studentsList = (BasicDBList) theObj.get("students");
for (int i = 0; i < studentsList.size(); i++) {
BasicDBObject studentObj = (BasicDBObject) studentsList.get(i);
String firstName = studentObj.getString("firstName");
String lastName = studentObj.getString("lastName");
String age = studentObj.getString("age");
String gender = studentObj.getString("gender");
Student student = new Student();
student.setFirstName(firstName);
student.setLastName(lastName);
student.setAge(age);
student.setGender(gender);
students.add(student);
}
}
回答by Mzzl
You generally use an ORM tool for that (though it wouldn't be meaningful to call it ORM in the case of a non relational database).
您通常为此使用 ORM 工具（尽管在非关系数据库的情况下将其称为 ORM 没有意义）。
There are several such tools. I like spring-data, which hides a lot of boiler plate code for you and gives you a simple, clean syntax. Something like this:
有几种这样的工具。我喜欢 spring-data，它为你隐藏了很多样板代码，并为你提供了一个简单、干净的语法。像这样的东西：
@Repository
public class UserRepositoryImpl implements UserRepository {
private MongoTemplate mongoTemplate;
@Autowired
public UserRepositoryImpl(MongoTemplate mongoTemplate) {
this.mongoTemplate = mongoTemplate;
}
@Override
public User findsUserByUsernameAndPassword(String userName, String encodedPassword) {
return mongoTemplate.findOne(query(where("userName").is(userName).and("encodedPassword").is(encodedPassword)), User.class);
}
}
With the Userclass defined as:
随着User类定义为：
@Document(collection = "users")
public class User {
private String userName;
private String encodedPassword;
// snip getters and setters
}
