所以我要做的是创建一个 CriteriaQuery 并为地图的键添加一个位置，但我得到一个 NullPointerException。
SQL中的类似以下内容（只是为了更好地解释我的意思）：
select test.* from test join test_translation on test_translation.id=test.id where test_translation.key='pt'
我成功地进行了 HQL 查询并使用了 index()，但我需要比这更动态的东西。这是有效的：
TypedQuery q = em.createQuery("from Test t join t.translations tt where index(tt)=?1",Test.class).setParameter(1, "pt");
我所有的代码来复制我的问题，这是一个很长的帖子，但它是完整的例子。我可能遗漏的任何信息都可以询问。
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>JpaTests</groupId>
<artifactId>JpaTests</artifactId>
<version>1.0</version>
<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.1.3.Final</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.9</version>
</dependency>
</dependencies>
</project>
持久性.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence">
<persistence-unit name="test" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.connection.username" value="root"/>
<property name="hibernate.connection.password" value="root"/>
<property name="hibernate.connection.url" value="jdbc:mysql://localhost/test"/>
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
<property name="hibernate.connection.autocommit" value="false"/>
<property name="hibernate.current_session_context_class" value="thread"/>
<property name="hibernate.show_sql" value="true"/>
<property name="hibernate.use_sql_comments" value="true"/>
<property name="hibernate.hbm2ddl.auto" value="create-drop"/>
</properties>
</persistence-unit>
</persistence>
测试.java
import javax.persistence.*;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
@Entity
public class Test implements Serializable {
@Embeddable
public static class TestTranslation {
private String text;
public TestTranslation() {
}
public TestTranslation(String text) {
this.text = text;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
}
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private long id;
@ElementCollection(fetch = FetchType.EAGER)
private Map<String, TestTranslation> translations = new HashMap<String, TestTranslation>();
@ElementCollection
private Map<String,String> map1=new HashMap<String, String>();
public Test() {
}
public Test(Map<String, TestTranslation> translationMap) {
this.translations=translationMap;
}
public Test(Map<String, TestTranslation> tr, Map<String, String> map1) {
this.translations=tr;
this.map1=map1;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public Map<String, TestTranslation> getTranslations() {
return translations;
}
public void setTranslations(Map<String, TestTranslation> translations) {
this.translations = translations;
}
public Map<String, String> getMap1() {
return map1;
}
public void setMap1(Map<String, String> map1) {
this.map1 = map1;
}
}
主.java
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.MapJoin;
import javax.persistence.criteria.Root;
import java.util.HashMap;
import java.util.Map;
public class Main {
public static void main(String[] args) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("test");
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
Map<String, Test.TestTranslation> tr = new HashMap<String, Test.TestTranslation>();
tr.put("pt", new Test.TestTranslation("teste"));
tr.put("en", new Test.TestTranslation("test"));
Map<String, String> map1 = new HashMap<String, String>();
map1.put("pt", "teste");
map1.put("en", "test");
Test test = new Test(tr,map1);
em.persist(test);
em.getTransaction().commit();
//got data time to make the query
em = emf.createEntityManager();
em.getTransaction().begin();
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Test> cq = cb.createQuery(Test.class);
Root<Test> root = cq.from(Test.class);
//tried a simpler map but it also fails with NullPointerException
MapJoin<Test, String, String> joinTranslations = root.joinMap("translations");
//MapJoin<Test, String, String> join = root.joinMap("map1");
cq = cq.where(cb.equal(joinTranslations.key(), "pt"));
//cq = cq.where(cb.equal(join.key(), "pt"));
TypedQuery<Test> q = em.createQuery(cq);
for (Test itm : q.getResultList()) {
System.out.println(itm.getId());
for (Map.Entry<String, Test.TestTranslation> entry : itm.getTranslations().entrySet()) {
System.out.println(entry.getKey() + ":" + entry.getValue().getText());
}
}
em.getTransaction().commit();
}
}