Hibernate报错：On release of batch it still contained JDBC statements

错误现象：Project和User使用注解多对一单向关联(@ManyToOne)

    // Project 类
    @ManyToOne
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

先new一个Project对象，并从数据库中取出User对象放入Project对象

此时使用session.save(project)报错：On release of batch it still contained JDBC statements

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错误分析：由于user对象是从数据库中取出，还缓存在session中，此时save(project)就报错

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解决办法：配置Cascade注解就可以了

    @ManyToOne
    @Cascade(value = CascadeType.SAVE_UPDATE) // 增加该注解即可
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

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解决办法二：用session.merge() 方法代替session.save() 即可