HibernateUnable to locate appropriate constructor on class原因分析

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通常我们喜欢将hql查询结果封装到POJO对象
syntax:
select new POJO(id,name) from POJO ;

这种封装需要POJO类提供对应构造器,POJO(id,name)构造方法。

但使用中经常会抛这样的异常:Unable to locate appropriate constructor on class。

出现这个异常需要检查以下几种情况:
1)参数构造器的参数类型是否正确
2)参数构造器的顺序和hql中的顺序是否一致
3)参数构造器的参数个数是否和hql中的个数一致
4)参数构造器的参数类型是否TimeStamp

其中第4种情况较为复杂

这里提供参数构造器的参数类型是TimeStamp的解决方法:
super.getHibernateTemplate().find("select new Student(id,name,date) from Student");

 1 实体类:
 2 public class Student {
 3 private Long id;
 4 private String name;
 5 private String address;
 6 private Timestamp date;
 7 public Long getId() {
 8    return id;
 9 }
10 public void setId(Long id) {
11    this.id = id;
12 }
13 public String getName() {
14    return name;
15 }
16 public void setName(String name) {
17    this.name = name;
18 }
19 public String getAddress() {
20    return address;
21 }
22 public void setAddress(String address) {
23    this.address = address;
24 }
25 public Timestamp getDate() {
26    return date;
27 }
28 public void setDate(Timestamp date) {
29    this.date = date;
30 }
31 public Student() {
32    super();
33 }
34 //注意些处的构造方法
35 public Student(Long id, String name, Object date) {
36 this.id=id;
37    this.name = name;
38    this.date = stringToTimestamp(date.toString());
39 }
40 
41 public static Timestamp stringToTimestamp(String dateStr){
42  
43    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
44    Calendar cal = Calendar.getInstance();
45    try {
46     Date date = sdf.parse(dateStr);
47     date.getTime();
48     cal.setTime(date);
49     return new Timestamp(cal.getTimeInMillis());
50    } catch (ParseException e) {
51     e.printStackTrace();
52    }
53  
54    cal.setTime(new Date());
55    return new Timestamp(cal.getTimeInMillis());
56 }
57 }

出处:http://blog.sina.com.cn/s/blog_4ad7c2540102uzkc.html








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