我正在使用 GlassFish 4.0 服务器和基于 JPA 的服务器端类，我想通过 JAX-RS 提供这些类。到目前为止，这对于简单实体来说效果很好。但是，例如，如果我有一个 @OneToMany 关系并且有一个链接实体，则服务器会返回 500 内部服务器错误。在这种情况下，服务器日志中不会记录任何内容。为了找到错误，我创建了一个小的自定义 JSP 页面来获取有关所发生情况的更多信息。代码就是这样：
Status: <%= pageContext.getErrorData().getStatusCode() %>
Throwable: <%= pageContext.getErrorData().getThrowable() %>
不幸的是，输出只是“状态：500 Throwable：null”
我自己的服务器端代码似乎运行正常（做了一些调试输出），但是出现了一些错误。在此示例中，除非存在链接的 IssueComment 实体，否则可以毫无问题地检索 User 和 Issue 类：
用户等级：
package my.application.model;
import static javax.persistence.FetchType.LAZY;
import java.io.Serializable;
import java.util.List;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.xml.bind.annotation.XmlRootElement;
/**
* The persistent class for the User database table.
*
*/
@XmlRootElement
@Entity(name="User")
@Table(name="User")
public class User implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="id")
private int id;
@Column(name="failedLogin")
private short failedLogin;
@Column(name="firstname")
private String firstname;
@Column(name="lastname")
private String lastname;
@Column(name="middlename")
private String middlename;
@Column(name="password")
private String password;
@Column(name="username")
private String username;
//bi-directional many-to-one association to IssueComment
@OneToMany(mappedBy="user", fetch = LAZY)
private List<IssueComment> issueComments;
//bi-directional many-to-one association to SignalComment
@OneToMany(mappedBy="user", fetch = LAZY)
private List<SignalComment> signalComments;
//bi-directional many-to-one association to SignalMeasure
@OneToMany(mappedBy="user", fetch = LAZY)
private List<SignalMeasure> signalMeasures;
public User() {
}
public int getId() {
return this.id;
}
// more getters and setters auto-generated by Eclipse
}
用户等级：
package my.application.model;
import java.io.Serializable;
import java.util.Date;
import java.util.List;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.xml.bind.annotation.XmlRootElement;
@NamedQuery(
name = "getSingleIssue",
query = "SELECT i FROM Issue i WHERE i.id = :id"
)
/**
* The persistent class for the Issue database table.
*
*/
@XmlRootElement
@Entity(name="Issue")
@Table(name="Issue")
public class Issue implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id")
private int id;
@Column(name="concernedModule")
private String concernedModule;
@Column(name="createdate")
@Temporal(TemporalType.TIMESTAMP)
private Date createdate;
@Column(name="duedate")
@Temporal(TemporalType.TIMESTAMP)
private Date duedate;
@Column(name="priority")
private int priority;
@Column(name="reminderdate")
@Temporal(TemporalType.TIMESTAMP)
private Date reminderdate;
@Column(name="responsibleUserId")
private int responsibleUserId;
@Column(name="sendingModule")
private String sendingModule;
@Column(name="severity")
private int severity;
@Column(name="status")
private int status;
@Column(name="title")
private String title;
// bidirectional many-to-one association to IssueComment
@OneToMany(mappedBy = "issue")
private List<IssueComment> issueComments;
public Issue() {
}
public int getId() {
return this.id;
}
// more getters and setters....
}
问题评论：
package my.application.model;
import java.io.Serializable;
import javax.persistence.*;
import java.util.Date;
/**
* The persistent class for the IssueComment database table.
*
*/
@Entity(name="IssueComment")
@Table(name="IssueComment")
public class IssueComment implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue
@Column(name="id")
private int id;
@Lob
@Column(name="comment")
private String comment;
@Temporal(TemporalType.TIMESTAMP)
@Column(name="time")
private Date time;
//bi-directional many-to-one association to Issue
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name="issueId")
private Issue issue;
//bi-directional many-to-one association to User
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name="userId")
private User user;
public IssueComment() {
}
public int getId() {
return this.id;
}
public void setId(int id) {
this.id = id;
}
// getters/setters....
}
网络服务如下：
package my.application.server.webservice;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.ext.Provider;
import org.glassfish.jersey.server.ResourceConfig;
import my.application.data.UserStorage;
import my.application.logger.Logger;
import my.application.model.Signal;
import my.application.model.SignalComment;
import my.application.model.User;
@Provider
@Path("User")
public class UserService extends ResourceConfig {
private UserStorage storage = new UserStorage();
public UserService() {
this.packages("my.application.model");
}
@Produces(MediaType.APPLICATION_XML)
@Path("load")
@GET
public User getUser(@QueryParam("id") int id) {
try {
Logger.getInstance().log("fetching id: " + id);
User u = storage.getUser(id);
Logger.getInstance().log("number of signal comments: " + u.getSignalComments().size());
SignalComment sc = u.getSignalComments().get(0);
Logger.getInstance().log("Signal 0 comment: " + sc.getComment());
Signal s = sc.getSignal();
Logger.getInstance().log("Signal subject: " + s.getSubject());
return u;
} catch (Exception e) {
e.printStackTrace();
}
// this code is not being reached (so no errors in this method):
Logger.getInstance().log("---EXCEPTION HAS BEEN THROWN---");
return null;
}
}
我放弃了客户端源代码，因为它是服务器端的，可以用普通浏览器复制，所以恕我直言，这里不需要客户端代码。