如何使用Criteria进行分组求和、排序、模糊查询

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Criteria进行分组求和、排序、模糊查询

工程框架使用的是spring data,但是spring data 提供的 JpaRepository 以及覆写JpaSpecificationExecutor接口并不能满足我的要求，我要进行模糊查询，并根据bookId对数量进行分组聚合，并获取数量最高的top n，由于模糊查询并不是必填条件，所以直接使用@Query注解感觉也不是很合适，于是采用Criteria来实现。

1.Entity如下

package com.example.springdatatest.repository.entity; import lombok.Data; import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table; @Table@Data@Entitypublic class TestEntity {     @Id    String testId;     @Column    public String regionCode;     @Column    public long count;     @Column    public String bookId;      @Column    public String libraryCode;}

2.repository如下

package com.example.springdatatest.repository; import com.example.springdatatest.repository.entity.TestEntity;import org.springframework.data.jpa.repository.JpaRepository;import org.springframework.data.jpa.repository.JpaSpecificationExecutor; public interface TestRepository extends JpaRepository,JpaSpecificationExecutor {}

3.service如下

package com.example.springdatatest.service; import com.example.springdatatest.repository.TestRepository;import com.example.springdatatest.repository.entity.TestEntity;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service; import javax.persistence.EntityManager;import javax.persistence.PersistenceContext;import javax.persistence.Tuple;import javax.persistence.criteria.*;import java.util.ArrayList;import java.util.List; @Servicepublic class TestService {     @Autowired    TestRepository testRepository;     @Autowired    @PersistenceContext    private EntityManager entityManager;      public void test(){        CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();        CriteriaQuery criteriaQuery = criteriaBuilder.createQuery(Tuple.class  );         Root root = criteriaQuery.from(TestEntity.class);         List predicateList = new ArrayList<>();        predicateList.add(criteriaBuilder.equal( root.get("libraryCode" ), "1" ));        predicateList.add(criteriaBuilder.like(root.get("regionCode"),"%"+"6101"+"%"));        Predicate[] p = new Predicate[predicateList.size()];        predicateList.toArray(p);         Path bookId = root.get("bookId");        Path bookCount = root.get("count");         criteriaQuery.where(p)                .multiselect(bookId,criteriaBuilder.sum(bookCount))                .groupBy(bookId)                .orderBy(criteriaBuilder.desc(criteriaBuilder.sum(bookCount)));         List list = entityManager.createQuery(criteriaQuery).setFirstResult(1)                .setMaxResults(1)                .getResultList();     }}

4.顺便提及一个不经意间的小错误

也是由于粗心，没有写这一句 predicateList.toArray(p); ，导致一直报空指针异常。

java.lang.NullPointerException
at org.hibernate.query.criteria.internal.predicate.CompoundPredicate.render(CompoundPredicate.java:166)
at org.hibernate.query.criteria.internal.predicate.CompoundPredicate.render(CompoundPredicate.java:115)
at org.hibernate.query.criteria.internal.predicate.CompoundPredicate.render(CompoundPredicate.java:105)
at org.hibernate.query.criteria.internal.QueryStructure.render(QueryStructure.java:248)
at org.hibernate.query.criteria.internal.CriteriaQueryImpl.interpret(CriteriaQueryImpl.java:292)
at org.hibernate.query.criteria.internal.compile.CriteriaCompiler.compile(CriteriaCompiler.java:149)
at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:3707)
at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:208)
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.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:350)
at com.sun.proxy.$Proxy81.createQuery(Unknown Source)
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.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:309)
at com.sun.proxy.$Proxy81.createQuery(Unknown Source)
at com.example.springdatatest.service.TestService.test(TestService.java:50)
at com.example.springdatatest.SpringdatatestApplicationTests.contextLoads(SpringdatatestApplicationTests.java:19)
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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:74)
at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:84)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

这只是实现的一个小demo，具体入参并没有体现，在此做一个记录。

Criteria进行模糊查询实现站内搜索功能

今天给网站新加入了一个站内搜索的功能，思想是：使用Criteria进行模糊查询。

Dao层的方法如下

//搜索方法public List findSearch(String scon) {        Session s =  getHibernateTemplate().getSessionFactory().openSession();        Criteria criteria =s.createCriteria(Question.class);        criteria.add(Expression.or(Expression.like("qdesc","%"+scon+"%"),Expression.like("qname","%"+scon+"%")));        return criteria.list();    }

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