'Bean没有一个没有参数错误的公共构造函数'，尽管显然有一个错误？

Question

我有一个EmailService EJB，它有一个非常简单的'send_email'方法。尽管显然有一个不带参数的公共构造函数，但我仍然接受了标题中的错误。以下是确切的错误和类代码。这很混乱。

错误：

[ERROR ] CNTR5007E: The websphere.jaxrs.service.EmailService bean class for the WebApiConsole#WebApiConsole.war#EmailService bean does not have a public constructor that does not take parameters.

在这里看到错误的详细信息（不多见）：http://pic.dhe.ibm.com/infocenter/wxdinfo/v6r1/index.jsp?topic=%2Fcom.ibm.websphere.messages.doc%2Fcom.ibm.ejs.container.container.html

代码：

package websphere.jaxrs.service; 

import javax.ejb.EJB; 
import javax.ejb.LocalBean; 
import javax.ejb.Stateless; 

import org.apache.commons.mail.Email; 
import org.apache.commons.mail.EmailException; 
import org.apache.commons.mail.SimpleEmail; 

import websphere.jaxrs.helpers.ContextFinder; 

    /** 
    * This class provides an interface for emailing messages. It uses server environment variables to configure SMTP server and port and authentication. 
    * 
    * @author me 
    * 
    */ 
    @Stateless 
    @LocalBean 
    public class EmailService { 

     @EJB ContextFinder ctf; 

     private static final String EMAIL_PASSWORD_JNDI_NAME = "EMAIL_PASSWORD"; 
     private static final String EMAIL_USERNAME_JNDI_NAME = "EMAIL_USERNAME"; 
     private static final String SMTP_SERVER_JNDI_NAME = "SMTP_SERVER"; 
     private static final String SMTP_PORT_JNDI_NAME = "SMTP_PORT"; 

     private String username; 
     private String password; 
     private String server; 
     private Integer port; 


     public EmailService() { 
      username = (String) ctf.lookup(EMAIL_USERNAME_JNDI_NAME); 
      password = (String) ctf.lookup(EMAIL_PASSWORD_JNDI_NAME); 
      server = (String) ctf.lookup(SMTP_SERVER_JNDI_NAME); 
      port = (Integer) ctf.lookup(SMTP_PORT_JNDI_NAME); 
     } 

     /** 
     * Sends an email to a specific user. 
     * 
     * @param sendTo 
     * @param subject 
     * @param message 
     */ 
     public void sendMail(String sendTo, String subject, String message) { 

      try { 
       Email email = new SimpleEmail(); 
       email.setHostName(server); 
       email.setSmtpPort(port); 
       email.setAuthentication(username, password); 
       email.setSSLOnConnect(true); 
       email.setFrom(username); 
       email.setSubject(subject); 
       email.setMsg(message); 
       email.addTo(sendTo); 
       email.send(); 
      } catch (EmailException e) { 
       System.err.println("Failed to email"); 
       e.printStackTrace(); 
      } 

     } 

    } 

我倾向于认为这是一个错误。我可能是错的，但是在上面的类中，一切都非常独立（没有其他配置，我知道它是必需的），并且我不断收到此错误。我尝试重建项目。

[编辑]我做了一些实验，非常具体，删除sendMail（）导致它没有错误。

Answer 1

为什么不从构造函数中移除初始化到@PostConstruct方法中？

@Stateless 
public class EmailService { 
    @EJB ContextFinder ctf; 

    private static final String EMAIL_PASSWORD_JNDI_NAME = "EMAIL_PASSWORD"; 
    private static final String EMAIL_USERNAME_JNDI_NAME = "EMAIL_USERNAME"; 
    private static final String SMTP_SERVER_JNDI_NAME = "SMTP_SERVER"; 
    private static final String SMTP_PORT_JNDI_NAME = "SMTP_PORT"; 

    private String username; 
    private String password; 
    private String server; 
    private Integer port; 

    @PostConstruct 
    public void init() { 
     username = (String) ctf.lookup(EMAIL_USERNAME_JNDI_NAME); 
     password = (String) ctf.lookup(EMAIL_PASSWORD_JNDI_NAME); 
     server = (String) ctf.lookup(SMTP_SERVER_JNDI_NAME); 
     port = (Integer) ctf.lookup(SMTP_PORT_JNDI_NAME); 
    } 

    public void sendMail(String sendTo, String subject, String message) { 
     // send mail 
    } 

} 

Answer 2

注射尚未发生。

简而言之：

1. 容器调用构造
2. 那么注入的领域获得注入
3. 那么postconstruct事情发生

因此提取查询，所建议的，成postconstruct方法

Answer 3

我宁愿注释你的结构或@Inject代替：

@Stateless 
@LocalBean 
public class EmailService { 

    .... 
    @Deprecated 
    public EmailService(){}  

    @Inject 
    public EmailService(ContextFinder ctf) { 
     username = (String) ctf.lookup(EMAIL_USERNAME_JNDI_NAME); 
     password = (String) ctf.lookup(EMAIL_PASSWORD_JNDI_NAME); 
     server = (String) ctf.lookup(SMTP_SERVER_JNDI_NAME); 
     port = (Integer) ctf.lookup(SMTP_PORT_JNDI_NAME); 
    } 

... 
} 

>>使用@PostConstruct是不是你有完全一样的。 init()方法在JUnit测试中不会在容器外工作。

您仍然需要提供默认的非参数化构造函数（The EJB 3.1 spec, section 4.9.2 Bean Classes的一部分）。