failed to lazily initialize a collection of role: , could not initialize proxy - no Session

hibernate 报错信息如下:

严重: Servlet.service() for servlet [spring2] in context with path [/convention] threw exception [Request processing failed; nested exception is org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.girltest.entity.Test2Boy.conventions, could not initialize proxy - no Session] with root cause
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.girltest.entity.Test2Boy.conventions, could not initialize proxy - no Session

有问题的代码:

public Test2Boy getConventions(int id){
        Convention c=new Convention();
        c.setStatus(Constant2.NEWS_STATUS_ON);
        Test2Boy test2Boy=(Test2Boy)super.getCurrentSession().createCriteria(clz)
                .add(Restrictions.idEq(id))

                .createAlias(Constant.property_conventions, "convention32")

                .add(Restrictions.eq("convention32.status", Constant2.NEWS_STATUS_ON))

                .uniqueResult();

        return test2Boy;
    }

说明:conventions 是Test2Boy的成员变量
报错的原因我也知道,因为

改为fetch = FetchType.EAGER 就好了.
但是我不想这样改.
因为查询Test2Boy列表时,不需要把conventions也查询出来.
所以我特意设置fetch方式为lazy.

但是在Test2Boy 的详情页面需要把conventions 查询出来.

Test2Boy的实体类如下:

package com.girltest.entity;

import java.util.List;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;

/***
 * 
 * @author huangweii
 * 2015年12月27日
 */
@Entity
@Table(name = "t_test_to_boy")
public class Test2Boy {
    private int id;
    /***
     * 测试
     */
    private String testcase;
    /***
     * 别名
     */
    private String alias;
    /***
     * 别名
     */
    private String alias2;
    /***
     * 最佳惯例
     */
    private Convention best;
    /***
     * 所有惯例
     */
    private List<Convention> conventions;
    /***
     * 更新时间
     */
    protected String updateTime;
    /***
     * 热度 <br>
     * 值越大,表示越受关注
     */
    protected int stars;
    /***
     * 1:有效;2:被删除
     */
    private int status;
    @Column(name="update_time")
    public String getUpdateTime() {
        return updateTime;
    }
    public void setUpdateTime(String updateTime) {
        this.updateTime = updateTime;
    }
    public int getStars() {
        return stars;
    }
    public void setStars(int stars) {
        this.stars = stars;
    }
    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getTestcase() {
        return testcase;
    }
    public void setTestcase(String testcase) {
        this.testcase = testcase;
    }
    public String getAlias() {
        return alias;
    }
    public void setAlias(String alias) {
        this.alias = alias;
    }
    public String getAlias2() {
        return alias2;
    }
    public void setAlias2(String alias2) {
        this.alias2 = alias2;
    }
    @ManyToOne( fetch = FetchType.LAZY)
    @JoinColumn(name = "best_convention_id")
    public Convention getBest() {
        return best;
    }
    public void setBest(Convention best) {
        this.best = best;
    }
    @ManyToMany( fetch = FetchType.LAZY)
    @JoinTable(name="t_mid_test_convention",
        joinColumns={@JoinColumn(name="test_id")},
        inverseJoinColumns={@JoinColumn(name="convention_id")}
        )
    @Fetch(FetchMode.SUBSELECT)
    public List<Convention> getConventions() {
        return conventions;
    }
    public void setConventions(List<Convention> conventions) {
        this.conventions = conventions;
    }
    public int getStatus() {
        return status;
    }
    public void setStatus(int status) {
        this.status = status;
    }

}

怎么办呢?

解决方法:使用参数CriteriaSpecification.LEFT_JOIN

public Test2Boy getConventions(int id){
        Convention c=new Convention();
        c.setStatus(Constant2.NEWS_STATUS_ON);
        Test2Boy test2Boy=(Test2Boy)super.getCurrentSession().createCriteria(clz)
                .add(Restrictions.idEq(id))

                .createAlias(Constant.property_conventions, "convention32",CriteriaSpecification.LEFT_JOIN)

                .add(Restrictions.eq("convention32.status", Constant2.NEWS_STATUS_ON))

                .uniqueResult();

        return test2Boy;
    }