java se 6项目是否支持eclipselink jpa2的criteria api?如果没有,那是我的问题。 我是否需要在 persistence.xml 中为条件 api 指定任何特殊内容?
这是我的条件查询:
final EntityType<Meaning> Meaning_ = em.getMetamodel().entity(Meaning.class);
final CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Integer> cq = cb.createQuery(Integer.class);
final Root<Meaning> meng = cq.from(Meaning.class);
cq.where(meng.get(Meaning_.lastPublishedDate)); //this attributes are not recognized/found
cq.select(meng.get(Meaning_.objId)); // " "
TypedQuery<Integer> q = em.createQuery(cq);
return q.getResultList();
这是我的意义实体:
@Entity
public class Meaning implements Serializable{
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int objId;
public int getObjId() {
return objId;
}
@Temporal(javax.persistence.TemporalType.DATE)
private Date lastPublishedDate = null;//never
public Date getLastPublishedDate(){
return lastPublishedDate;
}
}
最佳答案
关于您的代码
我没有检查条件查询本身的正确性,但正如 Chris 提到的,您将静态元模型类与 EntityType
混合在一起那不会暴露您要查找的内容。假设您的元模型类已生成,删除第一行并导入生成的 Meaning_
:
// final EntityType<Meaning> Meaning_ = em.getMetamodel().entity(Meaning.class);
final CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Integer> cq = cb.createQuery(Integer.class);
final Root<Meaning> meng = cq.from(Meaning.class);
cq.where(meng.get(Meaning_.lastPublishedDate)); // add the appropriate import
cq.select(meng.get(Meaning_.objId));
TypedQuery<Integer> q = em.createQuery(cq);
return q.getResultList();
关于静态(规范)元模型类的生成
这是我用来通过 EclipseLink 生成规范元模型类的 Maven 设置:
<project>
...
<repositories>
<!-- Repository for EclipseLink artifacts -->
<repository>
<id>EclipseLink Repo</id>
<url>http://www.eclipse.org/downloads/download.php?r=1&nf=1&file=/rt/eclipselink/maven.repo/</url>
</repository>
...
</repositories>
...
<pluginRepositories>
<!-- For the annotation processor plugin -->
<pluginRepository>
<id>maven-annotation-plugin</id>
<url>http://maven-annotation-plugin.googlecode.com/svn/trunk/mavenrepo</url>
</pluginRepository>
</pluginRepositories>
...
<dependencies>
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>eclipselink</artifactId>
<version>2.1.0</version>
</dependency>
<!-- optional - only needed if you are using JPA outside of a Java EE container-->
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>javax.persistence</artifactId>
<version>2.0.2</version>
</dependency>
<dependencies>
...
<build>
<plugins>
<plugin>
<groupId>org.bsc.maven</groupId>
<artifactId>maven-processor-plugin</artifactId>
<version>1.3.1</version>
<executions>
<execution>
<id>process</id>
<goals>
<goal>process</goal>
</goals>
<phase>generate-sources</phase>
<configuration>
<!-- Without this, the annotation processor complains about persistence.xml not being present and fail -->
<compilerArguments>-Aeclipselink.persistencexml=src/main/resources/META-INF/persistence.xml</compilerArguments>
<!-- For an unknown reason, the annotation processor is not discovered, have to list it explicitly -->
<processors>
<processor>org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor</processor>
</processors>
<!-- source output directory -->
<outputDirectory>${project.build.directory}/generated-sources/meta-model</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<inherited>true</inherited>
<configuration>
<source>1.6</source>
<target>1.6</target>
<compilerArgument>-proc:none</compilerArgument>
</configuration>
</plugin>
...
</plugins>
</build>
</project>
一些评论:
- EclipseLink 注释处理器由主要工件提供,无需添加额外的依赖项。
- 由于未知原因,未发现注释处理器,我必须将其明确列为
<processor>
. - 没有
-Aeclipselink.persistencexml
,注释处理器提示persistence.xml
不在场和失败。 - 我更喜欢在
target
下生成源代码(我想要一个clean
来清理它)。
有了这个配置,静态元模型类就可以正确地生成和编译了。
关于java - 为什么编译器不识别元模型属性?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3458742/