Spring Data JPA-无需@Transactional即可获取延迟加载的集合 [英] Spring Data JPA - Lazy Loaded collection fetched without @Transactional

问题描述

我的期望是，在事务范围内访问该集合时，应该获取一个延迟加载的集合.例如，如果我想获取一个集合，则可以调用foo.getBars.size().缺少活动的事务会导致异常，并显示错误消息，例如

My expectation is that a lazy loaded collection should be fetched when the collection is accessed within a transactional scope. For example, if I want to fetch a collection I can call foo.getBars.size(). The absence of an active transaction should result in an exception with an error message like

无法延迟初始化条形图的集合:....无法 初始化代理-没有会话

failed to lazily initialize a collection of bars: .... could not initialize proxy - no Session

但是，我注意到我的最新应用程序中的行为有所不同.我正在使用带有"data-jpa"启动器的Spring Boot 1.5.1.我过去曾经使用过Spring Boot，但是data-jpa入门版对我来说是新的.

However, I noticed that the behavior is different in my latest application. I'm using Spring Boot 1.5.1 with the "data-jpa" starter. I have used Spring Boot in the past, but the data-jpa starter is new for me.

请考虑以下情况.我有一个懒惰的ManyManMany集合.

Consider the following case. I have a lazy loaded ManyToMany collection.

@SuppressWarnings("serial")
@Entity
@Table(name = "foo")
public class Foo implements java.io.Serializable {
    ....
    private Set<Bar> bars = new HashSet<Bar>(0);
    ....

    @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinTable(name = "foo_bar_map",
        joinColumns = {@JoinColumn(name = "foo_id", nullable = false, updatable = false)},
        inverseJoinColumns = {@JoinColumn(name = "bar_id", nullable = false, updatable = false)})
    public Set<Bar> getBars() {
        return this.bars;
    }

    public void setBar(Set<Bar> bars) {
        this.bars = bars;
    }

我的服务方法未标记为事务性"，但我正在访问延迟加载的集合

My service method is NOT marked as Transactional but I am accessing a lazy loaded collection

@Service
public class FooServiceImpl implements FooService {

    @Autowired
    private FooRepository fooRepo;


    @Override
    public FooDTO findById(int fooId) {
        Foo foo = fooRepo.findOne(fooId);
        // The FooDTO constructor will access foo.getBars()  
        return new FooDTO(foo);
    }

对于FooDTO构造函数的上下文

And for context on the FooDTO constructor

public FooDTO(Foo foo) {
    ...
    for (Bar bar : foo.getBars()) {
        this.bars.add(bar);
    }
}

与我的期望和过去的经验相反，此代码成功执行并获取集合.此外，如果我在服务方法中抛出一个断点，则可以单步执行代码，并在日志中看到SQL语句，这些语句在调用fooRepo之后获取了这些条.调用fooRepo之后，我希望该交易会结束.

Contrary to my expectation and past experience, this code executes successfully and fetches the collection. Further, if I throw a breakpoint in my service method, I can step through the code and see the SQL statements in my logs that fetch the bars after my call to the fooRepo. After my call to fooRepo, I expect the transaction to be closed.

这是怎么回事?

推荐答案

Spring Boot默认情况下使用OpenEntityManagerInView拦截器.您可以通过将属性spring.jpa.open-in-view设置为false来关闭它.

Spring Boot uses an OpenEntityManagerInView interceptor by default. You can turn it off by setting the property spring.jpa.open-in-view to false.

请参见文档作为此(和其他)JPA属性的参考.

See the documentation for the reference about this (and other) JPA properties.

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