Question

我正在开发一个Java Web应用程序，我使用netbeans 8作为IDE，glassfissh作为服务器我试图从我需要使用的数据库中的Users表中获取数据JPA作为数据模型层用于此目的，

编辑虽然Entity是由MySQL数据库中的一个表中的netbeans生成的，但是有一些行，resultList从执行查询返回的Derby不返回{{1数据库，它是空的

在下面我提供了我的实体Java bean代码，它由netbeans IDE

自动生成

import java.io.Serializable;
import java.util.Date;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import javax.xml.bind.annotation.XmlRootElement;

/**
 *
 * @author Home
 */
@Entity
@Table(name = "users")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Users.findAll", query = "SELECT u FROM Users u"),
    @NamedQuery(name = "Users.findById", query = "SELECT u FROM Users u WHERE u.id = :id"),
    @NamedQuery(name = "Users.findByName", query = "SELECT u FROM Users u WHERE u.name = :name"),
    @NamedQuery(name = "Users.findByEmail", query = "SELECT u FROM Users u WHERE u.email = :email"),
    @NamedQuery(name = "Users.findByPassword", query = "SELECT u FROM Users u WHERE u.password = :password"),
    @NamedQuery(name = "Users.findByRememberToken", query = "SELECT u FROM Users u WHERE u.rememberToken = :rememberToken"),
    @NamedQuery(name = "Users.findByCreatedAt", query = "SELECT u FROM Users u WHERE u.createdAt = :createdAt"),
    @NamedQuery(name = "Users.findByUpdatedAt", query = "SELECT u FROM Users u WHERE u.updatedAt = :updatedAt")})
public class Users implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id")
    private Integer id;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 255)
    @Column(name = "name")
    private String name;
    // @Pattern(regexp="[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?", message="Invalid email")//if the field contains email address consider using this annotation to enforce field validation
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 255)
    @Column(name = "email")
    private String email;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 255)
    @Column(name = "password")
    private String password;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 255)
    @Column(name = "remember_token")
    private String rememberToken;
    @Basic(optional = false)
    @NotNull
    @Column(name = "created_at")
    @Temporal(TemporalType.TIMESTAMP)
    private Date createdAt;
    @Basic(optional = false)
    @NotNull
    @Column(name = "updated_At")
    @Temporal(TemporalType.TIMESTAMP)
    private Date updatedAt;
public Users() {
}

public Users(Integer id) {
    this.id = id;
}

public Users(Integer id, String name, String email, String password, String rememberToken, Date createdAt, Date updatedAt) {
    this.id = id;
    this.name = name;
    this.email = email;
    this.password = password;
    this.rememberToken = rememberToken;
    this.createdAt = createdAt;
    this.updatedAt = updatedAt;
}

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getEmail() {
    return email;
}

public void setEmail(String email) {
    this.email = email;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}

public String getRememberToken() {
    return rememberToken;
}

public void setRememberToken(String rememberToken) {
    this.rememberToken = rememberToken;
}

public Date getCreatedAt() {
    return createdAt;
}

public void setCreatedAt(Date createdAt) {
    this.createdAt = createdAt;
}

public Date getUpdatedAt() {
    return updatedAt;
}

public void setUpdatedAt(Date updatedAt) {
    this.updatedAt = updatedAt;
}

@Override
public int hashCode() {
    int hash = 0;
    hash += (id != null ? id.hashCode() : 0);
    return hash;
}

@Override
public boolean equals(Object object) {
    // TODO: Warning - this method won't work in the case the id fields are not set
    if (!(object instanceof Users)) {
        return false;
    }
    Users other = (Users) object;
    if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
        return false;
    }
    return true;
}

@Override
public String toString() {
    return "some string";
}

}

这是我的Servlet代码，我尝试获取数据库的Users

@PersistenceUnit
EntityManagerFactory emf;
emf.createEntityManager().createNamedQuery("Users.findAll").getResultList().size()

但是ResultList没有从数据库中获取任何数据这是来自服务器的日志，显示iit已连接到Derby

Config:   Connected: jdbc:derby://localhost:1527/sun-appserv-samples;;create=true
User: APP
Database: Apache Derby  Version: 10.10.1.3 - (1557168)
Driver: Apache Derby Network Client JDBC Driver  Version: 10.10.2.0 - (1582446)

编辑基于配置的whil我认为它应该连接到MySQL这是我的glassfish-resources.xml文件

<?xml version="1.0" encoding="UTF-8"?>


 <!DOCTYPE resources PUBLIC "-//GlassFish.org//DTD GlassFish Application Server 3.1 Resource Definitions//EN" "http://glassfish.org/dtds/glassfish-resources_1_5.dtd">
<resources>
    <jdbc-connection-pool allow-non-component-callers="false" associate-with-thread="false" 
                          connection-creation-retry-attempts="0" connection-creation-retry-interval-in-seconds="10"
                          connection-leak-reclaim="false" connection-leak-timeout-in-seconds="0" connection-validation-method="auto-commit" 
                          datasource-classname="com.mysql.jdbc.jdbc2.optional.MysqlDataSource" fail-all-connections="false" 
                          idle-timeout-in-seconds="300" is-connection-validation-required="false" is-isolation-level-guaranteed="true" 
                          lazy-connection-association="false" lazy-connection-enlistment="false" match-connections="false"
                          max-connection-usage-count="0" max-pool-size="32" max-wait-time-in-millis="60000" name="mysql_mysql_rootPool" 
                          non-transactional-connections="false" pool-resize-quantity="2" res-type="javax.sql.ConnectionPoolDataSource" 
                          statement-timeout-in-seconds="-1" steady-pool-size="8" validate-atmost-once-period-in-seconds="0"
                          wrap-jdbc-objects="false">
        <property name="serverName" value="localhost"/>
        <property name="portNumber" value="3306"/>
        <property name="databaseName" value="mydatabase"/>
        <property name="User" value="root"/>
        <property name="Password" value=""/>
        <property name="URL" value="jdbc:mysql://localhost:3306/mydatabase"/>
        <property name="driverClass" value="com.mysql.jdbc.Driver"/>
    </jdbc-connection-pool>
    <jdbc-resource enabled="true" jndi-name="realestateConnection" object-type="user" pool-name="mysql_mysql_rootPool"/>
</resources>

这是我的persistence.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" 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_1.xsd">
  <persistence-unit name="architectsPU" transaction-type="JTA">
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties>
      <property name="javax.persistence.schema-generation.database.action" value="create"/>
      <property name="eclipselink.logging.level" value="FINE"/>
    </properties>
  </persistence-unit>
</persistence>

编辑请帮助我如何解决这个问题，以及如何更改配置以便在部署文件时连接到正确的数据库，该文件告诉服务器要连接的数据源是否与`persistence.xml相同？如果不在哪里？

Answer 1

由于对问题的评论明确说明，您的JPA提供程序正在使用Apache Derby而不是您想要的数据库（mySQL）。这是因为您的 persistence.xml 并不打算指定要使用的数据源。您需要指定jtaDataSource（也可能是nonJtaDataSource）指向您的JTA MySQL DataSource，以便JPA提供程序获得使用您的DataSource所需的信息。

数据库不为空时，JPA实体返回null

1 个答案: