我有以下方法：
public ArrayList<Weapon> getDbWeapons()
{
ArrayList<Weapon> dbWeapons = new ArrayList<>();
EntityTransaction entr=em.getTransaction();
entr.begin();
TypedQuery<Weapon> query = em.createQuery("SELECT i FROM Weapon i", Weapon.class);
dbWeapons = new ArrayList<Weapon>(query.getResultList());
em.getTransaction().commit();
return dbWeapons;
}
public ArrayList<Armor> getDbArmors()
{
ArrayList<Armor> dbArmors = new ArrayList<>();
EntityTransaction entr=em.getTransaction();
entr.begin();
TypedQuery<Armor> query = em.createQuery("SELECT i FROM Armor i", Armor.class);
dbArmors = new ArrayList<Armor>(query.getResultList());
em.getTransaction().commit();
return dbArmors;
}
public ArrayList<Potion> getDbPotions()
{
ArrayList<Potion> dbPotions = new ArrayList<>();
EntityTransaction entr=em.getTransaction();
entr.begin();
TypedQuery<Potion> query = em.createQuery("SELECT i FROM Potion i", Potion.class);
dbPotions = new ArrayList<Potion>(query.getResultList());
em.getTransaction().commit();
return dbPotions;
我的问题是 - 我如何首先将方法调用到另一个方法（在同一个类中），将它们的内容合并到一个ArrayList，然后返回它？
谢谢你的回答！
那里的类项目（新方法的接口）：
package com.dke.ps.Items;
/**
* General class for an item containing common information sutch as id, name,
* description, path to an icon, price and type of an item.
* @author valecvit
* @author koresmi1
*/
public abstract class Item
{
/**
* Unique id of an item.
*/
public int itemid;
/**
* Name of an item.
*/
public String name;
/**
* Description of an item.
*/
public String description;
/**
* Relative path to item image.
*/
public String icon;
/**
* Type of an item.
*/
public int type;
/**
* Price of an item.
*/
public int price;
}
我的Table.Weapon类：
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package com.dke.ps.Tables;
import java.io.Serializable;
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.JoinColumn;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToOne;
import javax.persistence.Table;
import javax.xml.bind.annotation.XmlRootElement;
/**
*
* @author michal
*/
@Entity
@Table(name = "weapon")
@XmlRootElement
@NamedQueries({
@NamedQuery(name = "Weapon.findAll", query = "SELECT w FROM Weapon w")
, @NamedQuery(name = "Weapon.findByItemid", query = "SELECT w FROM Weapon w WHERE w.itemid = :itemid")
, @NamedQuery(name = "Weapon.findByName", query = "SELECT w FROM Weapon w WHERE w.name = :name")
, @NamedQuery(name = "Weapon.findByDescription", query = "SELECT w FROM Weapon w WHERE w.description = :description")
, @NamedQuery(name = "Weapon.findByIcon", query = "SELECT w FROM Weapon w WHERE w.icon = :icon")
, @NamedQuery(name = "Weapon.findByType", query = "SELECT w FROM Weapon w WHERE w.type = :type")
, @NamedQuery(name = "Weapon.findByPower", query = "SELECT w FROM Weapon w WHERE w.power = :power")
, @NamedQuery(name = "Weapon.findByPrice", query = "SELECT w FROM Weapon w WHERE w.price = :price")})
public class Weapon implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Basic(optional = false)
@Column(name = "itemid")
private Integer itemid;
@Column(name = "name")
private String name;
@Column(name = "description")
private String description;
@Column(name = "icon")
private String icon;
@Column(name = "type")
private Integer type;
@Column(name = "power")
private Integer power;
@Column(name = "price")
private Integer price;
@JoinColumn(name = "itemid", referencedColumnName = "id", insertable = false, updatable = false)
@OneToOne(optional = false)
private ItemsId itemsId;
public Weapon() {
}
public Weapon(Integer itemid) {
this.itemid = itemid;
}
public Integer getItemid() {
return itemid;
}
public void setItemid(Integer itemid) {
this.itemid = itemid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getIcon() {
return icon;
}
public void setIcon(String icon) {
this.icon = icon;
}
public Integer getType() {
return type;
}
public void setType(Integer type) {
this.type = type;
}
public Integer getPower() {
return power;
}
public void setPower(Integer power) {
this.power = power;
}
public Integer getPrice() {
return price;
}
public void setPrice(Integer price) {
this.price = price;
}
public ItemsId getItemsId() {
return itemsId;
}
public void setItemsId(ItemsId itemsId) {
this.itemsId = itemsId;
}
@Override
public int hashCode() {
int hash = 0;
hash += (itemid != null ? itemid.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 Weapon)) {
return false;
}
Weapon other = (Weapon) object;
if ((this.itemid == null && other.itemid != null) || (this.itemid != null && !this.itemid.equals(other.itemid))) {
return false;
}
return true;
}
@Override
public String toString() {
return "com.dke.ps.Tables.Weapon[ itemid=" + itemid + " ]";
}
}
这是com.dke.ps.Items包中的第二类武器
package com.dke.ps.Items;
/**
* Class for a weapon.
* @author valecvit
* @author koresmi1
*/
public class Weapon extends Item
{
/**
* Attack power of the weapon.
*/
public int power;
/**
* Initializes new weapon.
* @param id unique item id
* @param name name of item
* @param description description of item
* @param icon path to item image
* @param price price of item
* @param type type of item
* @param power power of item
*/
public Weapon(int id, String name, String description, String icon, int price, int type, int power)
{
this.itemid = id;
this.name = name;
this.description = description;
this.icon = icon;
this.price = price;
this.type = type;
this.power = power;
}
}
答案 0 :(得分：0)
只需创建List<Item> getAllItems()方法并将所有项目添加到单个列表中，例如Weapon查询：
public List<Item> getAllItems() {
List<Item> items = new ArrayList<Item>();
// Database-related code
items.addAll(new ArrayList<Weapon>(query.getResultList()));
// Same for 2 remaining Item subclasses
return items;
}
可能没有必要在getResultList()中包含ArrayList，请在getResultList()的文档中查看。
此外，您可以在一次交易中完成所有3个数据库查询。
答案 1 :(得分：0)
您可以创建一个调用现有方法的方法：
public List<Item> getAllItems()
{
List<Item> items = new ArrayList<>();
items.addAll(this.getDbWeapons());
items.addAll(this.getDbArmors());
items.addAll(this.getDbPotions());
return items;
}