hibernate级联查询中fetch取值的差异简观

做的是多对一的级联查询，
其中用到的实体类有

public class Students implements java.io.Serializable {

	// Fields

	private int id;
	private String name;
	private Integer age;

	// Constructors

	/** default constructor */
	public Students() {
	}

	/** minimal constructor */
	public Students(String name) {
		this.name = name;
	}

	/** full constructor */
	public Students(String name, Integer age) {
		this.name = name;
		this.age = age;
	}

	// Property accessors


	public String getName() {
		return this.name;
	}


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

	public Integer getAge() {
		return this.age;
	}

	public void setAge(Integer age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return "id="+id+";name="+name+";age="+age;
	}

	public int getId() {
		return id;
	}

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

public class BookList {
	private int id;
	private Long booklist_index;
	private Students students;
	
	
	public BookList() {
		super();
		// TODO Auto-generated constructor stub
	}
	public BookList( Long booklistIndex, Students students) {
		super();
		booklist_index = booklistIndex;
		this.students = students;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}


	public Long getBooklist_index() {
		return booklist_index;
	}
	public void setBooklist_index(Long booklistIndex) {
		booklist_index = booklistIndex;
	}
	public Students getStudents() {
		return students;
	}
	public void setStudents(Students students) {
		this.students = students;
	}
	@Override
	public String toString() {
		return "id="+id+"\t bookList_index="+booklist_index+"\t students="+students;
	}
}

配置文件中，需要在多的一端配置many-to-one代替proterty元素。
eg：

 <many-to-one name="students" cascade="save-update" fetch="select"  class="org.tiger.model.Students">
       	<column name="students_id"></column>
       </many-to-one>

在实验之中，设置fetch="select"可以join的另一个值：
1.当使用hql的query接口查询的时候，每次都是发出多条语句去查询，首先是查询多的一方的一个list，然后将这个list遍历代入外键去发出另一个sql语句去查一的那方。
而如果是使用Criteria接口去查询的时候，则如果设置为join是通过一个left outer join的外连接一条语句查询出来的。



以上是：hibernate级联查询中fetch取值的差异简观实验。具体的待将来深入研究的时候发掘。