今天在改写hibernate项目时，发现一个严重的问题，假如我想加二级缓存，那么就必须使用addentity（）方法来指定具体的实体类，
但是我一加具体的实体类时，查询语句就会多出多个无关联的查询语句，这个问题搞了我一下午，现在把这个问题贴出来
BaseDaoImpl.java
SQLQuery query = getSession().createSQLQuery(hql).addEntity(t.getClass()); query.setCacheable(true);
SubjectBizImpl.java
String sql="select s.id,ed.editionName,s.editionId,s.semester,s.subjectName,s.chapterCount,s.seq from subject s right join edition ed on s.editionId=ed.id"; Map<String,Object> param=new HashMap<String,Object>(); List subject=null; if(subjectPage!=null){ sql+=" where "; if(subjectPage.getEditionName()!=null && !"".equals(subjectPage.getEditionName().trim())){ sql+=" ed.editionName like '%"+subjectPage.getEditionName()+"%' and "; } if(subjectPage.getSemester()!=null && !"".equals(subjectPage.getSemester().trim())){ sql+=" s.semester like '%"+subjectPage.getSemester().trim()+"%' and "; } sql+=" 1=1"; } if(page==null || rows==null){ subject = baseDao.searchByPro(sql, null, null,param,new Subject()); }else{ //分页 int startPage=(page-1)*rows; sql+=" limit "+startPage+","+rows; subject= baseDao.searchByPro(sql, startPage, rows,param,new Subject()); } 当时这个代码运行下来，它总是有多个无关联的查询语句，后面我用了各种办法，发现只要你有这个 addEntity(t.getClass())方法，那么就会出现这个问题，后面我又仔细的看了一下subject这个映射类
@Entity @Table(name = "Subject") @Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE) public class Subject implements Serializable { /** * */ private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Integer id; @Column(length = 100, nullable = false) private String subjectName;// 课程名 @Column(nullable = false) private Integer chapterCount;// 所含章节数 @Column(length = 50, nullable = false) private String semester;// 课程所属学期 @Column private Integer seq; public Integer getSeq() { return seq; } public void setSeq(Integer seq) { this.seq = seq; } @ManyToOne @JoinColumn(name = "editionId", nullable = false) private Edition edition; @OneToMany(mappedBy = "subject") private Set<Chapter> chapters = new HashSet<Chapter>(); @OneToMany(mappedBy = "subject") private Set<PointInfo> pointInfos = new HashSet<PointInfo>(); @OneToMany(mappedBy="subject") private Set<PointPaper> pointPapers= new HashSet<PointPaper>(); public Set<PointPaper> getPointPapers() { return pointPapers; } public void setPointPapers(Set<PointPaper> pointPapers) { this.pointPapers = pointPapers; } public Set<PointInfo> getPointInfos() { return pointInfos; } public void setPointInfos(Set<PointInfo> pointInfos) { this.pointInfos = pointInfos; } public Set<Chapter> getChapters() { return chapters; } public void setChapters(Set<Chapter> chapters) { this.chapters = chapters; } public Edition getEdition() { return edition; } public void setEdition(Edition edition) { this.edition = edition; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getSubjectName() { return subjectName; } public void setSubjectName(String subjectName) { this.subjectName = subjectName; } public Integer getChapterCount() { return chapterCount; } public void setChapterCount(Integer chapterCount) { this.chapterCount = chapterCount; } public String getSemester() { return semester; } public void setSemester(String semester) { this.semester = semester; } 后面我通过问别人，最中解决了这个问题，在映射实体类里@ManyToOne这个注解，它有个默认的属性 FetchType fetch() default EAGER; 这个属性默认为懒加载为全部抓取，所以，那个查询语句总是会出现多个无关的语句最后在@ManyToOne这个注解里修改一下这个属性的值
@ManyToOne(fetch=FetchType.LAZY)将它改为延迟抓取LAZY，就这样，这个问题圆满解决了最后再说一点，使用这个属性一定要注意一下，它有可能会让你抓不到数据的，可以自己去了解一下懒加载
还有一个问题，假如你想要使用二级缓存机制，就一定要用到addentity()方法的，不然会报错的
