我正在使用JPA 2.1，Hibernate 4.3.6.Final和MySQL 5.5。我读过JPA 2.1支持调用本机数据库函数，但是我无法弄清楚如何调用MySQL的“GROUP_CONCAT”。我有以下代码......
final CriteriaBuilder builder = m_entityManager.getCriteriaBuilder();
final CriteriaQuery criteria = StringUtils.equals(orderByCol, "organization") ? builder.createQuery(Tuple.class) : builder.createQuery(User.class);
final Root<User> user = criteria.from(User.class);
…
final SetJoin<User, Organization> orgsJoin = orderByRoot.join(User_.organizations, JoinType.LEFT);
final Expression groupConcatExpr = builder.function("GROUP_CONCAT", String.class, orgsJoin.get(Organization_.name));
criteria.select(builder.tuple(user, groupConcatExpr))
.groupBy(user);
…
orderByExpr = orgsJoin.get(Organization_.name);
criteria.orderBy(orderByAscending == null || orderByAscending == true ? builder.asc(orderByExpr) : builder.desc(orderByExpr));
但我得到以下例外......
java.lang.IllegalStateException: No data type for node: org.hibernate.hql.internal.ast.tree.MethodNode
\-[METHOD_CALL] MethodNode: 'function (GROUP_CONCAT)'
+-[METHOD_NAME] IdentNode: 'GROUP_CONCAT' {originalText=GROUP_CONCAT}
\-[EXPR_LIST] SqlNode: 'exprList'
\-[DOT] DotNode: 'organizati2_.NAME' {propertyName=name,dereferenceType=PRIMITIVE,getPropertyPath=name,path=generatedAlias1.name,tableAlias=organizati2_,className=org.mainco.subco.organization.domain.Organization,classAlias=generatedAlias1}
+-[ALIAS_REF] IdentNode: 'organizati2_.id' {alias=generatedAlias1, className=org.mainco.subco.organization.domain.Organization, tableAlias=organizati2_}
\-[IDENT] IdentNode: 'name' {originalText=name}
at org.hibernate.hql.internal.ast.tree.SelectClause.initializeExplicitSelectClause(SelectClause.java:174)
at org.hibernate.hql.internal.ast.HqlSqlWalker.useSelectClause(HqlSqlWalker.java:924)
at org.hibernate.hql.internal.ast.HqlSqlWalker.processQuery(HqlSqlWalker.java:692)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:665)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:301)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:249)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:278)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:206)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:158)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:126)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:88)
at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:167)
at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:301)
at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:236)
at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1800)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:568)
at org.hibernate.jpa.criteria.CriteriaQueryImpl$1.buildCompiledQuery(CriteriaQueryImpl.java:336)
at org.hibernate.jpa.criteria.compile.CriteriaCompiler.compile(CriteriaCompiler.java:147)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:736)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:240)
at com.sun.proxy.$Proxy68.createQuery(Unknown Source)
at org.mainco.subco.user.repo.UserDaoImpl.findUsers(UserDaoImpl.java:120)
at org.mainco.subco.user.repo.UserDao2IT.testFindOrderByOrganizationAsc(UserDao2IT.java:624)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
答案 0 :(得分：-3)
对于JPA中的用户GROUP_CONCAT，以下是步骤：
1。）创建一个“GroupConcatFunction”类，如下所示：
import java.util.List;
import org.hibernate.QueryException;
import org.hibernate.dialect.function.SQLFunction;
import org.hibernate.engine.spi.Mapping;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.type.StandardBasicTypes;
import org.hibernate.type.Type;
public class GroupConcatFunction implements SQLFunction {
@Override
public boolean hasArguments() {
return true;
}
@Override
public boolean hasParenthesesIfNoArguments() {
return true;
}
@Override
public Type getReturnType(Type firstArgumentType, Mapping mapping)
throws QueryException {
return StandardBasicTypes.STRING;
}
@SuppressWarnings("rawtypes")
@Override
public String render(Type firstArgumentType, List arguments,
SessionFactoryImplementor factory) throws QueryException {
if (arguments.size() != 1) {
throw new QueryException("group_concat should have only one argument");
}
return "group_concat(" + arguments.get(0) + ")";
}
}
2。）我们将创建一个自定义方言，其中包含用方言注册我们的group_concat函数的代码：
import org.hibernate.dialect.MySQL5Dialect;
public class CustomMySql5Dialect extends MySQL5Dialect {
public CustomMySql5Dialect() {
super();
registerFunction("group_concat", new GroupConcatFunction());
}
}
3。）用自定义方言替换persistence.xml中的方言定义：
<property name="hibernate.dialect" value="<<pkg name>>.CustomMySql5Dialect" />
现在，您可以在条件查询中使用它。