也许我没有看到它，但是指定组有什么问题？
查询数据库困难（当前为空）：
public void persist(Msg message) {
LOG.info("\t" + message);
LOG.info("isOpen?" + em.isOpen());
em.getTransaction().begin();
int id = message.getId();
TypedQuery<Notes> q = em.createQuery("SELECT n "
+ "FROM Notes n WHERE n.messageId = :messageId "
+ "AND n.group = :group", Notes.class);
q.setParameter("messageId", message.getId()).setParameter("group", message.getGroup());
List<Notes> results = q.getResultList();
em.getTransaction().commit();
for (Notes o : results) {
LOG.info("object is \n\n" + o);
}
}
堆栈跟踪：
run:
May 10, 2012 7:17:17 AM net.bounceme.dur.usenet.controller.PropertiesReader getProps
INFO: NNTP.loadMessages...
[EL Info]: 2012-05-10 07:17:27.343--ServerSession(29959998)--EclipseLink, version: Eclipse Persistence Services - 2.3.0.v20110604-r9504
[EL Severe]: 2012-05-10 07:17:29.315--ServerSession(29959998)--Local Exception Stack:
Exception [EclipseLink-8025] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.JPQLException
Exception in thread "AWT-EventQueue-0" java.lang.ExceptionInInitializerError
Exception Description: Syntax error parsing the query [Notes.getByIdAndGroup: SELECT DISTINCT n FROM Notes n WHERE n.messageId = :messageId AND n.group=group], line 1, column 74: unexpected token [group].
Internal Exception: NoViableAltException(34@[792:1: comparisonExpressionRightOperand returns [Object node] : (n= arithmeticExpression | n= nonArithmeticScalarExpression | n= anyOrAllExpression );])
at net.bounceme.dur.usenet.swing.Frame.panelWithTable1PropertyChange(Frame.java:121)
at net.bounceme.dur.usenet.swing.Frame.access$100(Frame.java:12)
at net.bounceme.dur.usenet.swing.Frame$2.propertyChange(Frame.java:51)
数据库：
thufir@dur:~$
thufir@dur:~$ mysql -u java -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 141
Server version: 5.1.58-1ubuntu1 (Ubuntu)
Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL v2 license
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
mysql> describe nntp.notes;
+------------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+------------+------+-----+---------+-------+
| ID | bigint(20) | NO | PRI | NULL | |
| GROUP_ID | int(11) | NO | | NULL | |
| STAMP | date | NO | | NULL | |
| NOTE | text | YES | | NULL | |
| MESSAGE_ID | int(11) | NO | | NULL | |
| GROUP | text | NO | | NULL | |
+------------+------------+------+-----+---------+-------+
6 rows in set (0.03 sec)
mysql> quit;
Bye
thufir@dur:~$
这个类应该是Note还是Notes？同样，表格应该是 Note 还是 Notes？也许没关系。
实体：
package net.bounceme.dur.usenet.controller;
import java.io.Serializable;
import java.util.Date;
import javax.persistence.*;
import javax.xml.bind.annotation.XmlRootElement;
@Entity
@Table(name = "notes", catalog = "nntp", schema = "")
@XmlRootElement
@NamedQueries({
@NamedQuery(name = "Notes.findAll", query = "SELECT n FROM Notes n"),
@NamedQuery(name = "Notes.findById", query = "SELECT n FROM Notes n WHERE n.id = :id"),
@NamedQuery(name = "Notes.findByGroupId", query = "SELECT n FROM Notes n WHERE n.groupId = :groupId"),
@NamedQuery(name = "Notes.findByStamp", query = "SELECT n FROM Notes n WHERE n.stamp = :stamp"),
@NamedQuery(name = "Notes.findByMessageId", query = "SELECT n FROM Notes n WHERE n.messageId = :messageId"),
@NamedQuery(name = "Notes.getByIdAndGroup", query = "SELECT DISTINCT n FROM Notes n WHERE n.messageId = :messageId AND n.group=group"),
})
public class Notes implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Basic(optional = false)
@Column(name = "ID", nullable = false)
private Long id;
@Basic(optional = false)
@Column(name = "GROUP_ID", nullable = false)
private int groupId;
@Basic(optional = false)
@Column(name = "STAMP", nullable = false)
@Temporal(TemporalType.DATE)
private Date stamp;
@Lob
@Column(name = "NOTE", length = 65535)
private String note;
@Basic(optional = false)
@Column(name = "MESSAGE_ID", nullable = false)
private int messageId;
@Basic(optional = false)
@Lob
@Column(name = "GROUP", nullable = false, length = 65535)
private String group;
public Notes() {
}
public Notes(Long id) {
this.id = id;
}
public Notes(Long id, int groupId, Date stamp, int messageId, String group) {
this.id = id;
this.groupId = groupId;
this.stamp = stamp;
this.messageId = messageId;
this.group = group;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public int getGroupId() {
return groupId;
}
public void setGroupId(int groupId) {
this.groupId = groupId;
}
public Date getStamp() {
return stamp;
}
public void setStamp(Date stamp) {
this.stamp = stamp;
}
public String getNote() {
return note;
}
public void setNote(String note) {
this.note = note;
}
public int getMessageId() {
return messageId;
}
public void setMessageId(int messageId) {
this.messageId = messageId;
}
public String getGroup() {
return group;
}
public void setGroup(String group) {
this.group = group;
}
@Override
public int hashCode() {
int hash = 0;
hash += (id != null ? id.hashCode() : 0);
return hash;
}
@Override
public boolean equals(Object object) {
// TODO: Warning - this method won't work in the case the id fields are not set
if (!(object instanceof Notes)) {
return false;
}
Notes other = (Notes) object;
if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
return false;
}
return true;
}
@Override
public String toString() {
return "net.bounceme.dur.usenet.controller.Notes[ id=" + id + " ]";
}
}
现在我只使用一张表，但似乎无法获得有效的查询。