我正在使用 Jesey 在 java (JAX-RS) 中实现 Restful Web 服务。我在 Tomcat v7.0 上运行它，我使用 Hibernate 将数据映射到数据库 (MySQL)。我有一个查询来获取可交付成果的列表:
deliverables = (List<Deliverable>) session.createQuery("Select deliverable from
Task as t where t.project.id= :id And t.user.username = :name")
.setLong("id", projectId).setString("name", username).list();
它给了我一百个可交付成果，但我想在任务表中列出前三名。我很感激任何帮助。如何修改查询？
请注意，这三个可交付成果不应重复。
与 @FGreg 的答案有冲突。当我使用这些查询时，一切正常:
deliverables = (List<Deliverable>) session.createQuery(
"from Deliverable as d where d.project.id= :id").setLong("id", projectId).list();
long task_id;
for(Deliverable d: deliverables) {
task_id = (long) session.createQuery("Select Max(id) from Task as t where
t.deliverable.id = :id and t.user.username = :name")
.setLong("id", d.getId()).setString("name", username).uniqueResult();
d.setTask_id(task_id);
}
sortDeliverable(deliverables); // sort by Task_id
我认为在@FGreg提供的查询中，不考虑max(id)，例如一个可交付成果使用task_id = 31, 643两次。它可能会考虑Task_id = 31，这是错误的。有什么办法可以解决吗？
我尝试了@FGreg 查询，但没有不同。然后除了重复问题之外一切正常。
我尝试过这个:
deliverables = (List<Deliverable>) session.createQuery("from Deliverable as d inner join
Task as t where t.id = (select max(t1.id) from Task as t1 where t1.deliverable.id = d.id)
and d.project.id= :id and t.user.username = :name order by t.id desc")
.setMaxResults(3)
.setLong("id", projectId)
.setString("name", username)
.list();
我在堆栈跟踪中遇到了新错误:
Jul 13, 2012 5:03:10 PM org.hibernate.hql.internal.ast.ErrorCounter reportError
ERROR: Path expected for join!
Jul 13, 2012 5:03:10 PM org.hibernate.hql.internal.ast.ErrorCounter reportError
ERROR: Path expected for join!
Path expected for join!
at org.hibernate.hql.internal.ast.HqlSqlWalker.createFromJoinElement(HqlSqlWalker.java:371)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.joinElement(HqlSqlBaseWalker.java:3477)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3263)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3141)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:694)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:550)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:287)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:235)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:248)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:183)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:101)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:119)
at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:214)
at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:192)
at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1537)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:350)
at $Proxy65.createQuery(Unknown Source)
at se.softwerk.timelog.controller.DeliverableManager.deliverableList2(DeliverableManager.java:185)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$ResponseOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:205)
at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:288)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1469)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1400)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:708)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:928)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:539)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:298)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Jul 13, 2012 5:03:10 PM org.hibernate.hql.internal.ast.ErrorCounter reportError
ERROR: Invalid path: 't.id'
Jul 13, 2012 5:03:10 PM org.hibernate.hql.internal.ast.ErrorCounter reportError
ERROR: Invalid path: 't.id'
Invalid path: 't.id'
at org.hibernate.hql.internal.ast.util.LiteralProcessor.lookupConstant(LiteralProcessor.java:131)
at org.hibernate.hql.internal.ast.tree.DotNode.resolve(DotNode.java:219)
at org.hibernate.hql.internal.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:118)
at org.hibernate.hql.internal.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:114)
at org.hibernate.hql.internal.ast.HqlSqlWalker.resolve(HqlSqlWalker.java:883)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.expr(HqlSqlBaseWalker.java:1246)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.exprOrSubquery(HqlSqlBaseWalker.java:4252)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.comparisonExpr(HqlSqlBaseWalker.java:3730)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.logicalExpr(HqlSqlBaseWalker.java:1923)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.logicalExpr(HqlSqlBaseWalker.java:1848)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.logicalExpr(HqlSqlBaseWalker.java:1848)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.whereClause(HqlSqlBaseWalker.java:782)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:583)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:287)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:235)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:248)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:183)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:101)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:119)
at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:214)
at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:192)
at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1537)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:350)
at $Proxy65.createQuery(Unknown Source)
at se.softwerk.timelog.controller.DeliverableManager.deliverableList2(DeliverableManager.java:185)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
模型类:
@Entity
public class Task {
@Id
@GeneratedValue
private long id;
@ManyToOne(optional = false)
private User user;
@ManyToOne(optional = false)
private Project project;
@ManyToOne(optional = false)
private Deliverable deliverable;
}
可交付成果:
@Entity
public class Deliverable {
@Id
@GeneratedValue
private long id;
@Column(name = "short", nullable = false)
private String key;
@Column(nullable = false)
private String name;
@OneToMany(targetEntity = Task.class, mappedBy = "deliverable", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
@JsonIgnore
private Collection<Task> tasks;
@ManyToOne(optional = false, fetch = FetchType.EAGER)
@JoinColumn(name = "project")
private Project project;
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "parent")
private Deliverable parent;
@OneToMany(targetEntity = Deliverable.class, mappedBy = "parent", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
@JsonIgnore
private Collection<Deliverable> children;
}
最佳答案
我认为您正在要求按 ID 排序的 Task 中的前 3 个可交付成果。你可以尝试这样的事情:
编辑: 好的，我会再尝试一下。这应该会为您提供按 Task.id 排序的前 3 个 Deliverable，仅获取与 max(Task.id) 关联的 Deliverable )
deliverables =
(List<Deliverable>) session.createQuery(
"from Deliverable as d, Task as t
where t.deliverable.id = d.id and
t.id = (select max(t1.id) from Task t1 where t1.deliverable.id = d.id)
and d.project.id= :id
and t.user.username = :name
order by t.id desc")
.setMaxResults(3)
.setLong("id", projectId)
.setString("name", username)
.list();
关于mysql - 使用 MySQL 进行 SQL 查询，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11441313/