我正在使用hibernate来映射mysql数据库中的数据。
这是我的查询：
long id = (Long) session.createQuery("Select category.id from Project as p where p.id =:projectId").setLong("projectId", projectId).uniqueResult();
activities = session.createQuery("Select name from Activity as a where a.parent.id =:activityId").setLong("activityId", id).list();
它工作正常。如何将这两个查询合并为一个查询？
附加物
活动类：
@Entity
public class Activity implements BaseEntry, Comparable<Activity> {
private static final long serialVersionUID = 4937176332500551910L;
@Id
@GeneratedValue
private long id;
@Column(name = "short", unique = true, nullable = false)
private String key;
private String name;
@ManyToOne(fetch = FetchType.LAZY)
private Activity parent;
@OneToMany(targetEntity = Activity.class, mappedBy = "parent", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
@JsonIgnore
private Collection<Activity> children;
@OneToMany(targetEntity = Project.class, mappedBy = "category", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
@JsonIgnore
private Collection<Project> projects;
项目类：
@Entity
public class Project implements BaseEntry, Comparable<Project> {
private static final long serialVersionUID = 1911160043392595450L;
@Id
@GeneratedValue
private long id;
@Column(name = "short", unique = true, nullable = false)
private String key;
@Column(nullable = false)
private String name;
@ManyToOne(optional = false, fetch = FetchType.EAGER)
private Activity category;
我用了：
activities = session.createQuery("Select a.name from Activity as a where a.parent.id = (Select p.category.id from Project as p where p.id =:projectId)")
.setLong("projectId", projectId).list();
并得到一个错误：
Apache Tomcat/7.0.23 - 错误报告
HTTP 状态 500 -
类型异常报告
信息
描述服务器遇到一个内部错误 () 阻止它完成这个请求。
例外
org.codehaus.jackson.map.JsonMappingException：无法初始化代理 - 没有会话（通过引用链：java.util.ArrayList[0]->se.softwerk.timelog.model.Activity["parent"]->se. softwerk.timelog.model.Activity_$$_javassist_3["id"])
org.codehaus.jackson.map.JsonMappingException.wrapWithPath(JsonMappingException.java:218)
org.codehaus.jackson.map.JsonMappingException.wrapWithPath(JsonMappingException.java:183)
org.codehaus.jackson.map.ser.std.SerializerBase.wrapAndThrow(SerializerBase.java:140)
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:158)
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:122)
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:71)
org.codehaus.jackson.map.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:86)
org.codehaus.jackson.map.ser.StdSerializerProvider._serializeValue(StdSerializerProvider.java:610)
org.codehaus.jackson.map.ser.StdSerializerProvider.serializeValue(StdSerializerProvider.java:256)
org.codehaus.jackson.map.ObjectMapper.writeValue(ObjectMapper.java:1604)
org.codehaus.jackson.jaxrs.JacksonJsonProvider.writeTo(JacksonJsonProvider.java:558)
com.sun.jersey.json.impl.provider.entity.JacksonProviderProxy.writeTo(JacksonProviderProxy.java:160)
com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:306)
com.sun.jersey.server.impl.application.WebApplicationImpl。处理请求（WebApplicationImpl.java:1437）
com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:708)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
根本原因
org.hibernate.LazyInitializationException：无法初始化代理 - 没有会话
org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:149)
org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:195)
org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185)
se.softwerk.timelog.model.Activity $$_javassist_3.getId(Activity_$$_javassist_3.java)
sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）
sun.reflect.NativeMethodAccessorImpl.invoke（未知来源）
sun.reflect.DelegatingMethodAccessorImpl.invoke（未知来源）
java.lang.reflect.Method.invoke（未知来源）
org.codehaus.jackson.map.ser.BeanPropertyWriter.get(BeanPropertyWriter.java:483)
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:418)
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:122)
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:71)
org.codehaus.jackson.map.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:86)
org.codehaus.jackson.map.ser.StdSerializerProvider._serializeValue(StdSerializerProvider.java:610)
org.codehaus.jackson.map.ser.StdSerializerProvider.serializeValue(StdSerializerProvider.java:256)
org.codehaus.jackson.map.ObjectMapper.writeValue(ObjectMapper.java:1604)
org.codehaus.jackson.jaxrs.JacksonJsonProvider.writeTo(JacksonJsonProvider.java:558)
com.sun.jersey.json.impl.provider.entity.JacksonProviderProxy.writeTo(JacksonProviderProxy.java:160)
com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:306)
com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1437)
com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:708)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
note提供了根本原因的完整堆栈跟踪