解决Hibernate原生SQL映射问题

在问答里和论坛中，经常看到有人问，怎样将使用本地SQL查询出来的结果映射为值对象的问题，这里就Hibernate中提供的方法做个结论。前提，这里没有使用属性的延迟加载技术。

假设有个值对像，如下：

package test;   

public class Person {   
    private Long id;   
    private String name;   
    private Long age;   
    private Long phone;   
    private String address;   

    public Person(Long id, String name, Long age, Long phone, String address) {   
        this.id = id;   
        this.name = name;   
        this.age = age;   
        this.phone = phone;   
        this.address = address;   
    }   

    public Long getId() {   
        return id;   
    }   

    public void setId(Long id) {   
        this.id = id;   
    }   

    public String getName() {   
        return name;   
    }   

    public void setName(String name) {   
        this.name = name;   
    }   

    public Long getAge() {   
        return age;   
    }   

    public void setAge(Long age) {   
        this.age = age;   
    }   

    public Long getPhone() {   
        return phone;   
    }   

    public void setPhone(Long phone) {   
        this.phone = phone;   
    }   

    public String getAddress() {   
        return address;   
    }   

    public void setAddress(String address) {   
        this.address = address;   
    }   
}  

package test;

public class Person {
    private Long id;
    private String name;
    private Long age;
    private Long phone;
    private String address;

    public Person(Long id, String name, Long age, Long phone, String address) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.phone = phone;
        this.address = address;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Long getAge() {
        return age;
    }

    public void setAge(Long age) {
        this.age = age;
    }

    public Long getPhone() {
        return phone;
    }

    public void setPhone(Long phone) {
        this.phone = phone;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}  

如果查询全部五列记录的话，那么只要

List list = getHibernateTemplate().loadAll(Person.class);  

List list = getHibernateTemplate().loadAll(Person.class);  

如果只需要查询id,name,age三列记录呢？那么就要新增构造方法了，

public Person(Long id, String name, Long age) {   
    this.id = id;   
    this.name = name;   
    this.age = age;   
}  

	public Person(Long id, String name, Long age) {
		this.id = id;
		this.name = name;
		this.age = age;
	}    

然后呢，就可以通过HQL来进行查询。

List list = getHibernateTemplate().find("select new test.Person(id,name,age) from Person");  

List list = getHibernateTemplate().find("select new test.Person(id,name,age) from Person");    

这个方法通常可以满足需要了，只是如果，只需要查询id,name,phone三列记录的话，还新增构造方法？不行了，会出现构造方法冲突了。有个办法：

List list = getSession().createQuery("select id,name,phone from person").addScalar("id",Hibernate.Long).addScalar("name").addScalar("phone",Hibernate.Long).addEntity(Person.class);  

List list = getSession().createQuery("select id,name,phone from person").addScalar("id",Hibernate.Long).addScalar("name").addScalar("phone",Hibernate.Long).addEntity(Person.class);  

但是，这个只适用于存在Person实体的，如果Hibernate中没有进行Person映射的呢，系统中只存在一个JavaBean。

List list = getSession().createSQLQuery("select id \"id\",name \"name\",phone \"phone\" from person")   
                    .addScalar("id",Hibernate.Long).addScalar("name").addScalar("phone",Hibernate.Long)   
                    .setResultTransformer(Transformers.aliasToBean(Person.class)));  

List list = getSession().createSQLQuery("select id \"id\",name \"name\",phone \"phone\" from person")
					.addScalar("id",Hibernate.Long).addScalar("name").addScalar("phone",Hibernate.Long)
					.setResultTransformer(Transformers.aliasToBean(Person.class)));    

那么Hibernate就会自动将查出来的三列内容组装到VO对象中去，只是代码量有点大，而且名称都需要重新定义为小写的，在Oracle中查出来的列都默认为大写的（不知道其它数据库怎么样）

这个办法就不依赖于构造方法了，只需要定义私有变量，设置getter/setter方法就行了。

不过如果更猛点的，根本就没有JavaBean对象可以填充怎么办，Hibernate可以将查出来的列组装到集合类中去。如Map。

 
List list = getSession().createSQLQuery("select * from person")   
                    .setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP);  

List list = getSession().createSQLQuery("select * from person")
                    .setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP); 

除了这个Transformers还可以将列转化为List。

List list = getSession().createSQLQuery("select * from person")   
                    .setResultTransformer(Transformers.T0_LIST);  

List list = getSession().createSQLQuery("select * from person")
                    .setResultTransformer(Transformers.T0_LIST);

到此，还可以通过继承Transformers将结果映射为其它对象，不累述了，基本功能够用了。