hibernate inner join Path expected for join!

[9876-]

先贴代码：
POJO

public class ForumPost {
	private int pid;
	private int fid;
	private int backCount;
	private String ptitle;
	private int user_id;
	private String user_name;
	private Date subject_time;
	
	public ForumPost(int pid, int fid, String ptitle, int backCount,
			int user_id, String user_name,Date subject_time) {
		this.pid=pid;
		this.fid=fid;
		this.ptitle=ptitle;
		this.backCount=backCount;
		this.user_id=user_id;
		this.user_name=user_name;
		this.subject_time=subject_time;
	}	

	public int getPid() {
		return pid;
	}

	public void setPid(int pid) {
		this.pid = pid;
	}

	public int getFid() {
		return fid;
	}

	public void setFid(int fid) {
		this.fid = fid;
	}

	public int getBackCount() {
		return backCount;
	}

	public void setBackCount(int backCount) {
		this.backCount = backCount;
	}

	public String getPtitle() {
		return ptitle;
	}

	public void setPtitle(String ptitle) {
		this.ptitle = ptitle;
	}

	public int getUser_id() {
		return user_id;
	}

	public void setUser_id(int user_id) {
		this.user_id = user_id;
	}

	public Date getSubject_time() {
		return subject_time;
	}

	public void setSubject_time(Date subject_time) {
		this.subject_time = subject_time;
	}
	
	public String getUser_name() {
		return user_name;
	}

	public void setUser_name(String user_name) {
		this.user_name = user_name;
	}
}

@Entity
@Table(name="forum_post_subject")
public class ForumPostSubject {
	@ManyToOne(fetch=FetchType.LAZY)
	@JoinColumn(name="user_id")
	public User getUser() {
		return user;
	}
	public void setUser(User user) {
		this.user = user;
	}
	@Id
	public int getPid() {
		return pid;
	}
	public void setPid(int pid) {
		this.pid = pid;
	}
	public int getFid() {
		return fid;
	}
	public void setFid(int fid) {
		this.fid = fid;
	}
	public String getPtitle() {
		return ptitle;
	}
	public void setPtitle(String ptitle) {
		this.ptitle = ptitle;
	}
	public Date getSubject_time() {
		return subject_time;
	}
	public void setSubject_time(Date subject_time) {
		this.subject_time = subject_time;
	}
	@Column(name="back_count")
	public int getBackCount() {
		return backCount;
	}
	public void setBackCount(int backCount) {
		this.backCount = backCount;
	}
	private int pid;
	private int fid;
	private String ptitle;
	private Date subject_time;
	private int backCount;
	private User user;
	
}

@Entity
@Table(name="t_user")
public class User {
	
	private int user_id;
	private String user_name;
	private String password;
	private String mail;
	private Date create_time;
	private Set<ForumPostSubject> fps;
	@Id
	public int getUser_id() {
		return user_id;
	}
	public void setUser_id(int user_id) {
		this.user_id = user_id;
	}
	@OneToMany(fetch = FetchType.LAZY,mappedBy="user")
	public Set<ForumPostSubject> getFps() {
		return fps;
	}
	public void setFps(Set<ForumPostSubject> pfs) {
		this.fps = pfs;
	}
	
	public String getUser_name() {
		return user_name;
	}
	public void setUser_name(String user_name) {
		this.user_name = user_name;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public String getMail() {
		return mail;
	}
	public void setMail(String mail) {
		this.mail = mail;
	}
	public Date getCreate_time() {
		return create_time;
	}
	public void setCreate_time(Date create_time) {
		this.create_time = create_time;
	}
}

Dao：

@Repository
public class ForumPostSubjectDao implements IForumPostSubjectDao {
	@Resource
	SessionFactory mySessionFactory;

	@Override
	public List<ForumPost> getPostSubjects(int section_id) {
		Session session = mySessionFactory.getCurrentSession();
		session.beginTransaction();
		String hql = "select new com.unei.Model.ForumPost(f.pid,f.fid,f.ptitle,f.backCount,u.user_id,u.user_name,f.subject_time) from ForumPostSubject f inner join User u where f.fid="
				+ section_id;
		System.out.println(hql);
		Query query = session.createQuery(hql);
		List<ForumPost> subjects = query.list();
		session.getTransaction().commit();
		return subjects;
	}

}

数据库表结构：

CREATE TABLE `t_user` (
	`user_id` INT(11) NOT NULL AUTO_INCREMENT,
	`create_time` DATETIME NULL DEFAULT NULL,
	`mail` VARCHAR(255) NULL DEFAULT NULL,
	`password` VARCHAR(255) NULL DEFAULT NULL,
	`user_name` VARCHAR(255) NULL DEFAULT NULL,
	PRIMARY KEY (`user_id`)
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB
AUTO_INCREMENT=4;

CREATE TABLE `forum_post_subject` (
	`pid` INT(10) NOT NULL AUTO_INCREMENT COMMENT '帖子id',
	`fid` INT(10) NOT NULL COMMENT '帖子板块id',
	`ptitle` VARCHAR(100) NOT NULL COMMENT '帖子主题',
	`back_count` INT(11) NOT NULL COMMENT '回帖数量',
	`user_id` INT(10) NOT NULL COMMENT '发帖用户id',
	`subject_time` DATETIME NOT NULL COMMENT '发帖时间',
	PRIMARY KEY (`pid`)
)
COMMENT='论坛帖子数据表'
COLLATE='utf8_general_ci'
ENGINE=InnoDB
AUTO_INCREMENT=3;

错误信息：
2013-07-29 16:43:45,582 ERROR org.hibernate.hql.internal.ast.ErrorCounter.reportError:54 - Path expected for join!
2013-07-29 16:43:45,583 ERROR org.hibernate.hql.internal.ast.ErrorCounter.reportError:50 - Path expected for join!
Path expected for join!
at org.hibernate.hql.internal.ast.HqlSqlWalker.createFromJoinElement(HqlSqlWalker.java:369)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.joinElement(HqlSqlBaseWalker.java:3645)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3431)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3309)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:706)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:562)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:299)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:247)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:248)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:183)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:105)
..............
2013-07-29 16:43:45,591 ERROR org.hibernate.hql.internal.ast.ErrorCounter.reportError:54 - Invalid path: 'u.user_id'
2013-07-29 16:43:45,591 ERROR org.hibernate.hql.internal.ast.ErrorCounter.reportError:50 - Invalid path: 'u.user_id'
Invalid path: 'u.user_id'
at org.hibernate.hql.internal.ast.util.LiteralProcessor.lookupConstant(LiteralProcessor.java:119)
at org.hibernate.hql.internal.ast.tree.DotNode.resolve(DotNode.java:219)
at org.hibernate.hql.internal.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:118)
at org.hibernate.hql.internal.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:114)
at org.hibernate.hql.internal.ast.tree.DotNode.resolveSelectExpression(DotNode.java:660)
...........
2013-07-29 16:43:45,593 ERROR org.hibernate.hql.internal.ast.ErrorCounter.reportError:54 - Unable to locate appropriate constructor on class [com.unei.Model.ForumPost]
[cause=org.hibernate.PropertyNotFoundException: no appropriate constructor in class: com.unei.Model.ForumPost]
2013-07-29 16:43:45,594 ERROR org.hibernate.hql.internal.ast.ErrorCounter.reportError:50 - Unable to locate appropriate constructor on class [com.unei.Model.ForumPost]
[cause=org.hibernate.PropertyNotFoundException: no appropriate constructor in class: com.unei.Model.ForumPost]
Unable to locate appropriate constructor on class [com.unei.Model.ForumPost]
[cause=org.hibernate.PropertyNotFoundException: no appropriate constructor in class: com.unei.Model.ForumPost]
at org.hibernate.hql.internal.ast.tree.ConstructorNode.resolveConstructor(ConstructorNode.java:187)
at org.hibernate.hql.internal.ast.tree.ConstructorNode.prepare(ConstructorNode.java:152)
at org.hibernate.hql.internal.ast.HqlSqlWalker.processConstructor(HqlSqlWalker.java:1019)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectExpr(HqlSqlBaseWalker.java:2279)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectExprList(HqlSqlBaseWalker.java:2145)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectClause(HqlSqlBaseWalker.java:1451)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:571)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:299)
............

初学ssh，大家帮忙看看问题出在哪里，谢谢

[9876-]

自己解决了 String hql = "select new com.unei.Model.ForumPost(f.pid,f.fid,f.ptitle,f.backCount,u.user_id,u.user_name,f.subject_time) from ForumPostSubject f inner join f.user u where f.fid=" + section_id; hibernate sql语法不对。