将 MongoDB 驱动程序 POJO 与 Java 一起使用

Question

EDIT: I can use the POJO example with the suggested post to output a list of users in the console, but no Object id as shown below. Is that the problem causing output not showing to the JSP page?

User [email=didi@abc.com, fullName=Didi Dee, password=asdfwle]
User [email=lucy@abc.com, fullName=Lucy Liu, password=lalla]

What I expect the result like below, that show user details under each heading on the browser,

Here is the new method to list user in DAO class

@Override
public List<User> listAll() {
    List<User> userList = new ArrayList<User>();    
    database.getCollection("User", User.class).find().into(userList);
        for (User u : userList) {
        System.out.println(u.toString());
    }

    return userList;
}

My service class

public List<User> listUser() {
    List<User> userList = userDAO.listAll();            
    return userList;
}

The Controller

UserService userService = new UserService(request, response);

List<User> userList = userService.listUser();

request.setAttribute("userList", userList); // for jsp to get Attribute

String list_user_page = "user_list.jsp";
RequestDispatcher rd = request.getRequestDispatcher(list_user_page);
rd.forward(request, response);

The JSP to show the output.

<c:forEach items="${userList}" var="user" begin="1">
    <tr>            
        <td>${user.userId}</td>
        <td>${user.email}</td>
        <td>${user.fullName}</td>


        <td><a href="edit_user?id=${user.userId}">Edit</a> &nbsp; <a
            href="javascript:void(0);" class="deleteLink" id="${user.userId}">Delete</a>
        </td>
    </tr>
</c:forEach>

Answer 1

Assuming the following:

You've included

CodecRegistry pojoCodecRegistry = fromRegistries(MongoClientSettings.getDefaultCodecRegistry(),
                                  fromProviders(PojoCodecProvider.builder().automatic(true).build()));

Your database contains records in the following format:

> db.User.find().pretty()
{
    "_id" : ObjectId("5f7f92c4d91d2c38583dbfba"),
    "fullname" : "Stu Dent",
    "email" : "student@uni.versity",
    "password" : "passWord"
}
{
    "_id" : ObjectId("5f7f9497d91d2c38583dbfbb"),
    "fullname" : "A. N. Other",
    "email" : "another@uni.versity",
    "password" : "strongerPassWord_1"
}

User is defined as a bean like this:

public class User
{
    private String fullname;
    private String email;
    private String password;
    
    public User()
    {
        // Default bean constructor
    }

    public String getFullname()
    {
        return fullname;
    }

    public void setFullname(String fullname)
    {
        this.fullname = fullname;
    }

    public String getEmail()
    {
        return email;
    }

    public void setEmail(String email)
    {
        this.email = email;
    }

    public String getPassword()
    {
        return password;
    }

    public void setPassword(String password)
    {
        this.password = password;
    }

    @Override
    public String toString()
    {
        return "User [fullname=" + fullname + ", email=" + email + ", password=" + password + "]";
    }
}

The following code will read the contents of the database into the userList List:

List<User> userList = new ArrayList<User>();
db.getCollection("User", User.class).find().into(userList);

To output the list:

for (User u : userList)
{
    System.out.println(u.toString());
}

Result:

User [fullname=Stu Dent, email=student@uni.versity, password=passWord]
User [fullname=A. N. Other, email=another@uni.versity, password=strongerPassWord_1]

If you insist on looping through the individual records, then I would suggest:

FindIterable<Document> userTbl = db.getCollection("User").find();

for (Document doc: userTbl)
{
    User user = new User();
    user.setFullname(doc.getString("fullname"));
    user.setEmail(doc.getString("email"));
    user.setPassword(doc.getString("password"));
    
    System.out.println("User = " + user.toString());
}

Which produces:

User = User [fullname=Stu Dent, email=student@uni.versity, password=passWord]
User = User [fullname=A. N. Other, email=another@uni.versity, password=strongerPassWord_1]

Answer 2

The reason I can't show the user list because I forgot put the database connection to my controller that different from people used to do with JPA annotation and add a JPA layer on it.

response.setContentType("text/html");
MongoDB.getMongoDB();

Especially thanks Spuggiehawk for the suggested answer to write less code during a hard time debuggin.