HQL 语句中的 length() 不起作用
length() in HQL statement not working
所以我在 HQL 语句方面遇到了一些问题。语句 node where node.dflag=? and length(node.path)=? and node.rootEntityId=? 应该是基于 this reference - section 14.10. Expressions.
的有效 HQL 语句
StringBuilder hql = new StringBuilder(100);
hql.append("from ").append(SystemComponentRef.class.getName()).append(" node where node.dflag=? and length(node.path)=? and node.rootEntityId=?");
List<?> list = db.find(SystemComponentRef.class, hql.toString(), 0, 8, SystemEntity.SYS_ROOT_ENTITY_ID);
但是，当我尝试 运行 我的网络服务器上的代码时（使用 tomcat），我得到这个错误：
[localhost-startStop-1] ERROR backend.HibernateEntityDao - Executing hql statement from backend.SystemComponentRef node where node.dflag=? and length(node.path)=? and node.rootEntityId=? has incurred an error
org.springframework.orm.hibernate3.HibernateQueryException: could not resolve property: path of: backend.SystemComponentRef [from backend.SystemComponentRef node where node.dflag=? and length(node.path)=? and node.rootEntityId=?]; nested exception is org.hibernate.QueryException: could not resolve property: path of: backend.SystemComponentRef [from backend.SystemComponentRef node where node.dflag=? and length(node.path)=? and node.rootEntityId=?]
at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:656)
at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412)
at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:412)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:339)
at backend.HibernateEntityDao.find(HibernateEntityDao.java:107)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:198)
at com.sun.proxy.$Proxy57.find(Unknown Source)
at backend.EntitySupporterDealImpl.find(EntitySupporterDealImpl.java:82)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:198)
at com.sun.proxy.$Proxy63.find(Unknown Source)
at backend.SystemComponentDealImpl.getSecurityRootNode(SystemComponentDealImpl.java:214)
at backend.SystemInitTaskImpl.createRootDef(SystemInitTaskImpl.java:209)
at backend.SystemInitTaskImpl.runInitTask(SystemInitTaskImpl.java:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:344)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:295)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:130)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:396)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1507)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:521)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
at org.springframework.beans.factory.support.AbstractBeanFactory.getObject(AbstractBeanFactory.java:293)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:290)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:191)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:636)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:938)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:410)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:306)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4727)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5189)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:752)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:728)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:734)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:596)
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1805)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
这些是我的 gradle 依赖项：
compile group: 'org.springframework', name: 'spring-core', version: '3.2.16.RELEASE'
compile group: 'org.springframework', name: 'spring-web', version: '3.2.16.RELEASE'
compile group: 'org.hibernate', name: 'hibernate-core', version: '3.6.10.Final'
compile group: 'org.hibernate', name: 'hibernate-validator', version: '5.4.1.Final'
compile group: 'org.hibernate.hql', name: 'hibernate-hql-parser', version: '1.1.0.Final'
当我删除 length() 部分时，它工作正常。
hql.append("from ").append(SystemComponentRef.class.getName()).append(" d where d.dflag=? and d.rootEntityId=?");
List<?> list = db.find(SystemComponentRef.class, hql.toString(), 0, SystemEntity.SYS_ROOT_ENTITY_ID);
//this code works fine
我不能在我的 HQL 语句中使用 length()，我错过了什么？
如果您需要更多信息，请告诉我。
编辑：
TRoot.java 包含 dflag 和 rootEntityId
@Entity
@Table(name = "sysreference")
public class SystemComponentRef extends TRoot{
private String name;
protected String path;
protected String parentId;
protected Integer treeRecycleFlag;
protected Integer treeDeleteFlag;
@Column(name = "name")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Column(name = "parent_id")
public String getParentId() {
return parentId;
}
public void setParentId(String parentId) {
this.parentId = parentId;
}
@Column(name = "path")
public String getPath() {
return path;
}
public void setPath(String path) {
this.path = path;
}
@Column(name = "recycle_flag")
public Integer getTreeRecycleFlag() {
return treeRecycleFlag == null ? 0 : treeRecycleFlag;
}
public void setTreeRecycleFlag(Integer treeRecycleFlag) {
this.treeRecycleFlag = treeRecycleFlag;
}
@Column(name = "delete_flag")
public Integer getTreeDeleteFlag() {
return treeDeleteFlag == null ? 0 : treeDeleteFlag;
}
public void setTreeDeleteFlag(Integer treeDeleteFlag) {
this.treeDeleteFlag = treeDeleteFlag;
}
}
这与使用 length() 和 HQL 无关。
这是一个封装问题，因为在您的 SystemComponentRef bean 中，您将 path 声明为 protected，因此无法从 length(node.path) 中的 HQL 查询访问它，因为在Hibernate中，HQL 是一种面向对象的查询语言，类似于SQL，但不是对表和列进行操作， HQL 使用持久性 对象 及其属性。
这就是你得到异常的原因：
could not resolve property: path of: backend.SystemComponentRef [from backend.SystemComponentRef node where node.dflag=? and length(node.path)=?
也就是说属性 path 无法解析，也就是找不到（无法访问）
解法：
您需要将修饰符更改为 private 并使用 accessors 以便它遵守封装规则并且可以在您的 class 包之外访问，并且您需要记住Protected fields in base class are bad.
我建议您查看 Controlling Access to Members of a Class Java Tutorial 了解更多详情。
所以我在 HQL 语句方面遇到了一些问题。语句 node where node.dflag=? and length(node.path)=? and node.rootEntityId=? 应该是基于 this reference - section 14.10. Expressions.
StringBuilder hql = new StringBuilder(100);
hql.append("from ").append(SystemComponentRef.class.getName()).append(" node where node.dflag=? and length(node.path)=? and node.rootEntityId=?");
List<?> list = db.find(SystemComponentRef.class, hql.toString(), 0, 8, SystemEntity.SYS_ROOT_ENTITY_ID);
但是，当我尝试 运行 我的网络服务器上的代码时（使用 tomcat），我得到这个错误：
[localhost-startStop-1] ERROR backend.HibernateEntityDao - Executing hql statement from backend.SystemComponentRef node where node.dflag=? and length(node.path)=? and node.rootEntityId=? has incurred an error
org.springframework.orm.hibernate3.HibernateQueryException: could not resolve property: path of: backend.SystemComponentRef [from backend.SystemComponentRef node where node.dflag=? and length(node.path)=? and node.rootEntityId=?]; nested exception is org.hibernate.QueryException: could not resolve property: path of: backend.SystemComponentRef [from backend.SystemComponentRef node where node.dflag=? and length(node.path)=? and node.rootEntityId=?]
at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:656)
at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412)
at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:412)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:339)
at backend.HibernateEntityDao.find(HibernateEntityDao.java:107)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:198)
at com.sun.proxy.$Proxy57.find(Unknown Source)
at backend.EntitySupporterDealImpl.find(EntitySupporterDealImpl.java:82)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:198)
at com.sun.proxy.$Proxy63.find(Unknown Source)
at backend.SystemComponentDealImpl.getSecurityRootNode(SystemComponentDealImpl.java:214)
at backend.SystemInitTaskImpl.createRootDef(SystemInitTaskImpl.java:209)
at backend.SystemInitTaskImpl.runInitTask(SystemInitTaskImpl.java:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:344)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:295)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:130)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:396)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1507)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:521)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
at org.springframework.beans.factory.support.AbstractBeanFactory.getObject(AbstractBeanFactory.java:293)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:290)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:191)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:636)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:938)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:410)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:306)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4727)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5189)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:752)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:728)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:734)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:596)
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1805)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
这些是我的 gradle 依赖项：
compile group: 'org.springframework', name: 'spring-core', version: '3.2.16.RELEASE'
compile group: 'org.springframework', name: 'spring-web', version: '3.2.16.RELEASE'
compile group: 'org.hibernate', name: 'hibernate-core', version: '3.6.10.Final'
compile group: 'org.hibernate', name: 'hibernate-validator', version: '5.4.1.Final'
compile group: 'org.hibernate.hql', name: 'hibernate-hql-parser', version: '1.1.0.Final'
当我删除 length() 部分时，它工作正常。
hql.append("from ").append(SystemComponentRef.class.getName()).append(" d where d.dflag=? and d.rootEntityId=?");
List<?> list = db.find(SystemComponentRef.class, hql.toString(), 0, SystemEntity.SYS_ROOT_ENTITY_ID);
//this code works fine
我不能在我的 HQL 语句中使用 length()，我错过了什么？
如果您需要更多信息，请告诉我。
编辑：
TRoot.java 包含 dflag 和 rootEntityId
@Entity
@Table(name = "sysreference")
public class SystemComponentRef extends TRoot{
private String name;
protected String path;
protected String parentId;
protected Integer treeRecycleFlag;
protected Integer treeDeleteFlag;
@Column(name = "name")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Column(name = "parent_id")
public String getParentId() {
return parentId;
}
public void setParentId(String parentId) {
this.parentId = parentId;
}
@Column(name = "path")
public String getPath() {
return path;
}
public void setPath(String path) {
this.path = path;
}
@Column(name = "recycle_flag")
public Integer getTreeRecycleFlag() {
return treeRecycleFlag == null ? 0 : treeRecycleFlag;
}
public void setTreeRecycleFlag(Integer treeRecycleFlag) {
this.treeRecycleFlag = treeRecycleFlag;
}
@Column(name = "delete_flag")
public Integer getTreeDeleteFlag() {
return treeDeleteFlag == null ? 0 : treeDeleteFlag;
}
public void setTreeDeleteFlag(Integer treeDeleteFlag) {
this.treeDeleteFlag = treeDeleteFlag;
}
}
这与使用 length() 和 HQL 无关。
这是一个封装问题，因为在您的 SystemComponentRef bean 中，您将 path 声明为 protected，因此无法从 length(node.path) 中的 HQL 查询访问它，因为在Hibernate中，HQL 是一种面向对象的查询语言，类似于SQL，但不是对表和列进行操作， HQL 使用持久性 对象 及其属性。
这就是你得到异常的原因：
could not resolve property: path of: backend.SystemComponentRef [from backend.SystemComponentRef node where node.dflag=? and length(node.path)=?
也就是说属性 path 无法解析，也就是找不到（无法访问）
解法：
您需要将修饰符更改为 private 并使用 accessors 以便它遵守封装规则并且可以在您的 class 包之外访问，并且您需要记住Protected fields in base class are bad.
我建议您查看 Controlling Access to Members of a Class Java Tutorial 了解更多详情。