java - Hibernate 使用 @LazyToOne(LazyToOneOption.NO_PROXY) 进行延迟加载

Question

我有一个在 JBoss AS 7.2 上运行 Hibernate 4.2.21 的应用程序

我们目前有一些 @OneToOne 关系，由于 known limitations of lazy loading ，总是会在反面急切地获取。

为了启用反向关系的延迟加载，我正在尝试启用构建时字节码检测。

这是我到目前为止所做的...

1) 使用 maven-antrun-plugin 激活检测(我尝试了 hibernate-enhance-maven-plugin，但无法让它工作，但这是另一个问题)，我现在在构建日志中得到以下 Maven 输出:

[INFO] --- maven-antrun-plugin:1.7:run (Instrument domain classes) @ MyApp-entities ---
[INFO] Executing tasks

instrument:
[instrument] starting instrumentation
[INFO] Executed tasks

2)接下来我将所有@OneToOne关系注释如下......

    @OneToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "client", optional=false)
    @LazyToOne(LazyToOneOption.NO_PROXY)
    public ClientPrefs getClientPrefs() {
        return clientPrefs;
    }

    public void setClientPrefs(ClientPrefs clientPrefs) {
        this.clientPrefs = clientPrefs;
    }

3) 然后我添加 implement FieldHandled到 @Entity 类以及私有(private)字段、getter 和 setter:

private FieldHandler fieldHandler;

成功...我现在在部署日志中得到以下输出:

15:54:09,720 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 56) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.Session
15:54:09,730 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 57) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.Session
15:54:09,969 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 56) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.Client
15:54:09,970 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 57) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.Client
15:54:09,999 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 56) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.Country
15:54:10,003 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 57) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.Country
15:54:10,054 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 56) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.Pool
15:54:10,054 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 57) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.Pool
15:54:10,569 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 56) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.User
15:54:10,624 INFO  [org.hibernate.tuple.entity.EntityMetamodel] (ServerService Thread Pool -- 57) HHH000157: Lazy property fetching available for: uk.co.myapp.entities.User

关系现在不再急切加载...但它们也不会延迟加载，它们只是默默地返回 null。

我尝试删除 FieldHandled接口(interface)和FieldHandler来自实体的字段，因为我不确定这是否有必要，此后我不再得到 'HHH000157: Lazy property fetching available for:'启动时显示消息，默认情况下会返回到急切加载。

我在这里遗漏了什么吗？ hibernate 文档并未明确说明如何实际设置

编辑:根据评论添加 Ant 任务配置:

<build>
        <plugins>
               <plugin>
                    <artifactId>maven-antrun-plugin</artifactId>
                    <version>1.7</version>
                    <executions>
                        <execution>
                            <phase>process-classes</phase>
                            <id>Instrument domain classes</id>
                            <configuration>
                                <target name="instrument">
                                    <taskdef name="instrument"
                                        classname="org.hibernate.tool.instrument.javassist.InstrumentTask">
                                        <classpath>
                                            <path refid="maven.dependency.classpath" />
                                            <path refid="maven.plugin.classpath" />
                                        </classpath>
                                    </taskdef>
                                    <instrument verbose="true">
                                        <fileset dir="${project.build.outputDirectory}">
                                            <include name="MyApp-entities/co/uk/myapp/entities/*.class" />
                                        </fileset>
                                    </instrument>
                                </target>
                            </configuration>
                            <goals>
                                <goal>run</goal>
                            </goals>
                        </execution>
                    </executions>
                    <dependencies>
                        <dependency>
                            <groupId>org.hibernate</groupId>
                            <artifactId>hibernate-core</artifactId>
                            <version>4.2.21.Final</version>
                        </dependency>

                        <dependency>
                            <groupId>org.javassist</groupId>
                            <artifactId>javassist</artifactId>
                            <version>3.18.1-GA</version>
                        </dependency>
                    </dependencies>
                </plugin>
           </plugins>
    </build>

Answer 1

@LazyToOne(LazyToOneOption.NO_PROXY)需要<property name="hibernate.ejb.use_class_enhancer" value="true"/>在你的 persistance.xml 中

懒惰，在请求引用时返回加载的真实对象(此选项强制执行字节码增强，如果类未增强，则回退到 PROXY)应避免此选项，除非您无法承担使用代理的费用

NO_PROXY option