從 Postman 發送 GET 請求以測驗我的端點時遇到問題。相同的 NamedQueries 之前僅使用一個 Schema 與 Derby 一起作業，因此無需區分。我現在已更改為在本地 Docker 實體中運行的 DB2，并且正在使用 Maven 運行 Open-Liberty Framework 來創建端點。我收到以下錯誤。我是否需要使用物體映射創建一個 orm.xml 檔案，或者做其他事情來解決這個問題？如果可能，我更愿意在沒有更多 xml 檔案的情況下執行此操作。
郵差：
錯誤 500：java.lang.NullPointerException：無法呼叫 >"javax.persistence.EntityManager.createNamedQuery(String, java.lang.Class)" 因為“this.em”為空
馬文：
[INFO] [ERROR ] CWWJP0015E: org.eclipse.persistence.jpa.PersistenceProvider 持久性提供程式嘗試為 jpa-unit 持久性單元創建容器物體管理器工廠時發生錯誤。發生以下錯誤：例外 [EclipseLink-28019] (Eclipse Persistence Services - 2.7.9.v20210604-2c549e2208): org.eclipse.persistence.exceptions.EntityManagerSetupException
[INFO] 例外描述：PersistenceUnit [jpa-unit] 部署失敗。關閉此 PersistenceUnit 的所有工廠。
[INFO] 內部例外：例外 [EclipseLink-0] (Eclipse Persistence Services - 2.7.9.v20210604-2c549e2208): org.eclipse.persistence.exceptions.JPQLException
[INFO] 例外描述：編譯問題 [SELECT u FROM Sankofa.Users你]。
[INFO] [14, 29] 'Sankofa.Users u' 不能是 FROM 子句的第一個宣告。
用戶道
package dao;
import java.util.List;
import java.util.concurrent.TimeoutException;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.hyperledger.fabric.gateway.ContractException;
import javax.enterprise.context.RequestScoped;
import models.*;
@RequestScoped
public class UserDao {
//DB2 Methods
@PersistenceContext(name = "jpa-unit")
private EntityManager em;
public void createUser(Users user){
em.persist(user);
}
public Users readUser(int userID){
return em.find(Users.class, userID);
}
//NEED TO DO set return limit to 20
public List<Users> readAllUsers(){
return em.createNamedQuery("Users.findAll", Users.class).getResultList();
}
public void updateUser(Users user){
em.merge(user);
}
public void deleteUser(Users userID){
em.remove(userID);
}
public List<Users> findUser(String email){
return em.createNamedQuery("Users.findUser", Users.class)
.setParameter("email", email)
.getResultList();
}
public void createHistory(History hist){
em.persist(hist);
}
//wait this doesnt do anything?
public Users readHistory(int userID){
return em.find(Users.class, userID);
}
public List<History> readAllHistory(){
return em.createNamedQuery("History.findAll", History.class).getResultList();
}
}
用戶
package models;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;
import javax.json.Json;
import javax.json.JsonArrayBuilder;
import javax.json.JsonObject;
import javax.json.JsonObjectBuilder;
import javax.persistence.*;
import java.time.LocalDate;
@Entity
@Table(name = "Users")
@NamedQueries({
@NamedQuery(name = "Users.findAll", query = "SELECT u FROM Users u"),
@NamedQuery(name = "Users.findUser", query = "SELECT usr FROM Users usr WHERE usr.email = :email")
})
public class Users {
private static JsonObjectBuilder builder = Json.createObjectBuilder();
@GeneratedValue(strategy = GenerationType.AUTO)
@Id
@Column(name = "userId")
private int id;
@Column(name = "firstName")
private String firstName;
@Column(name = "lastName")
private String lastName;
@Column(name = "gender")
private String gender;
@Column(name = "address")
private String address;
@Column(name = "email")
private String email;
@Column(name = "password")
private String password;
@Column(name = "dateOfBirth")
private LocalDate dateOfBirth;
持久化檔案
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.2"
xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd">
<persistence-unit name="jpa-unit" transaction-type="JTA">
<mapping-file>orm.xml</mapping-file>
<properties>
<!-- Connection Specific -->
<property name="hibernate.dialect" value="org.hibernate.dialect.DB2Dialect"/>
<property name="javax.persistence.schema-generation.database.action" value="create" />
<property name="javax.persistence.schema-generation.create-database-schemas" value="true" />
<property name="javax.persistence.schema-generation.scripts.action" value="create" />
<property name="javax.persistence.schema-generation.scripts.create-target" value="create.ddl"/>
</properties>
</persistence-unit>
</persistence>
服務器.xml
<server description="Obdoblock REST Server">
<featureManager>
<feature>jaxrs-2.1</feature>
<feature>openapi-3.1</feature>
<feature>jpa-2.2</feature>
<feature>cdi-2.0</feature>
</featureManager>
<httpEndpoint
httpPort="${default.http.port}"
httpsPort="${default.https.port}"
id="defaultHttpEndpoint"
host="*"
/>
<webApplication
location="hyperledger-api.war"
contextRoot="${app.context.root}"
/>
<!-- DB2 Library Configuration -->
<library id="DB2JCCLib">
<file name="${shared.resource.dir}/jcc-11.5.6.0" />
</library>
<dataSource id="DefaultDataSource" jndiName="jdbc/db2">
<jdbcDriver libraryRef="jdbcLib"/>
<properties.db2.jcc
databaseName="testdb"
serverName="localhost"
portNumber="50000"
user="****" password="****"
/>
</dataSource>
</server>
版本：
- Docker：20.10.8，構建 3967b7d
- DB2：ibm/db2 docker 映像版本 11.5.6
- Maven：3.8.3
- Java：JDK 14.0.2
如果需要更多詳細資訊，我很樂意提供。謝謝，迪倫
uj5u.com熱心網友回復：
如何使用@NamedQuery 指定來自不同 DB2 模式的表
AFAIK，您不能在查詢級別配置架構值。在 Entity 下定義的所有命名查詢預計將針對相同的模式執行。
可以通過 orm.xml 映射檔案在持久性單元級別設定資料庫模式：
orm.xml
<entity-mappings ... > <persistence-unit-metadata> <persistence-unit-defaults> <schema>Sankofa</schema> </persistence-unit-defaults> </persistence-unit-metadata> . . . </entity-mappings>持久化檔案
<persistence ... > <persistence-unit name="foo"> <mapping-file>orm.xml</mapping-file> </persistence-unit> </persistence>對于 EclipseLink，可以配置一個 SessionCustomizer 類
public class FooSessionCustomizer implements org.eclipse.persistence.config.SessionCustomizer { @Override public void customize(Session session) throws Exception { session.getLogin().setTableQualifier("Sankofa"); } }持久化檔案
<persistence ... > <persistence-unit name="foo"> <properties> <property name="eclipselink.session.customizer" value="foo.customizer.FooSessionCustomizer" /> </properties> </persistence-unit> </persistence>@Table 注釋有一個“schema”元素來配置物體級別的架構
@Table(name = "Users", schema = "Sankofa")
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