java-如何在JPA中为电子邮件返回多个列？

Question

I wrote a program where I let my program endlessly pick up records from my emailqueue table so that it can process the records and send the email to outsiders.First the code is like below:

 MySqlConnect con=new MySqlConnect();
    public PreparedStatement preparedStatement = null;

    public Connection con1 = con.connect();



    //pick up queue and send email
    public void email() throws Exception {


        try{

            while(true) {
                String sql = "SELECT id,user,subject,recipient,content FROM emailqueue WHERE status='Pending' ";
                PreparedStatement statement = con1.prepareStatement(sql);
                ResultSet rs = statement.executeQuery();



                while (rs.next()) {

                    String subject = rs.getString("subject");

                    String recipient = rs.getString("recipient");

                    String content = rs.getString("content");

                    String id = rs.getString("id");
                    String username = rs.getString("user");

                    String emailStatus = "DONE";
                    String errormsg=sendEmail(recipient, subject, content, id,username);
                    if (!errormsg.equals("")) {
                        emailStatus = "FAILED";

                    }
                    TerminalLogger.printMsg("Status  : " + emailStatus);

                }
                statement.close();
                rs.close();

            }

As you can see,I used JDBC driver to get the value of each column in the table and passed them to sendEmail where it does it's work to send email.Sure,so far everything works flawlessly.

Now,I want to achieve the same goal by using JPA because I want to learn more about it and i'm new to it.So I added a database mapping to my email table,like below:

Emailqueue.java

@Entity
@Table(name = "emailqueue")

public class Emailqueue {
    private long ulnodeid;
    private String user;
    private String subject;
    private String recipient;
    private String content;
    private String status;

    @Id
    @Column(name = "ID")
    public long getUlnodeid() {
        return ulnodeid;
    }

    public void setUlnodeid(long ulnodeid) {
        this.ulnodeid = ulnodeid;
    }

    @Basic
    @Column(name = "USER")
    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    @Basic
    @Column(name = "SUBJECT")
    public String getSubject() {
        return subject;
    }

    public void setSubject(String subject) {
        this.subject = subject;
    }

    @Basic
    @Column(name = "RECIPIENT")
    public String getRecipient() {
        return recipient;
    }

    public void setRecipient(String recipient) {
        this.recipient = recipient;
    }

    @Basic
    @Column(name = "CONTENT")
    public String  getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    @Basic
    @Column(name = "STATUS")
    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }







    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Emailqueue that = (Emailqueue) o;
        return ulnodeid == that.ulnodeid &&
                user == that.user &&
                Objects.equals(subject, that.subject) &&
                Objects.equals(recipient, that.recipient) &&
                Objects.equals(content, that.content) &&
                Objects.equals(status, that.status);
    }

    @Override
    public int hashCode() {
        return Objects.hash(ulnodeid, user,subject,recipient,content,status);
    }
}

I wrote a method to retrieve records from the table using Entity Manager,below:

public Emailqueue getrecords() {
        try {

            String sql = "select object(o) from Emailqueue as o where " +
                    "status='" + "Pending" + "'";

            List resList = em.createQuery(sql).getResultList();
            if (resList == null) {
                throw new Exception("Error with selection query.");
            }

            if (resList.size() > 0) {
                return (Emailqueue) resList.get(0);
            }

           // msg = "Setting <" + name + "> not found.";

            return null;
        } catch (Exception e) {

            msg = CoreUtil.wrapMsg(CoreUtil.FUNC_ERROR,
                    this.getClass().getName(), "get(" + "Pending" + ")", e.getMessage());


            return null;
        }
    }

I mainly need recipient,subject,content,id and username records so i could pass it to the method. How would I retrieve values for each row where the status is pending in this case using JPA?

Edit:

Using a for loop:

public void email() throws Exception {


        try{

            while(true) {

                String sql = "select p.id,p.user,p.subject,p.recipient,p.content from Emailqueue p where " +
                        "status='Pending'";
                List<Emailqueue> emailList = em.createQuery(sql).getResultList();
                for (Emailqueue obj : emailList) {
                    String emailStatus = "DONE";
                    String errormsg=sendEmail(obj.getRecipient(), obj.getSubject(), obj.getContent(),obj.getUlnodeid(),obj.getUser());
                    if (!errormsg.equals("")) {
                        emailStatus = "FAILED";
                    }
                    TerminalLogger.printMsg("Status  : " + emailStatus);
                }

            }

Answer 1

Try replacing the query call with:

List<Emailqueue> res = em.createQuery("SELECT e from Emailqueue e WHERE e.status='Pending'",
                                          Emailqueue.class).getResultList();

This will return a list of matching instances as Java objects (entities), which you can easily work with by calling getters/setters, for example (using the sendEmail method from your question):

for (Emailqueue eq : res) {
   sendStatus = sendEmail(eq.getRecipient(), eq.getSubject(), eq.getContent(), eq.getId(), eq.getUsername());
}

Or, better yet, change the signature of sendEmail to sendEmail(Emailqueue eq) and call the getters in the method.