xpages - 用java为xpages构建一个缓存查找系统

Question

我们有许多在多个应用程序中使用的查找数据库，我试图找出通过 Java 函数或 OSGi 插件库中的 bean 使这些查找数据库可用的最佳和最有效的方法。

我想要实现的是创建一个函数的某种方式，我可以传入一个查找键和一个字段名称，该函数将返回正确的值和可能的对象类型(以处理数据时间值)。它还需要在应用程序级别缓存该值大约一个小时，因为这些查找文档根本不会改变。

通常，我希望将它们用于显示目的，这样我只需将 key 存储在我的笔记文档中，然后使用类似以下内容的内容在屏幕上显示我需要的内容

<xp:text escape="true" id="computedField1">
    <xp:this.value><![CDATA[#{javascript:com.mycompany.lookup.GetDoc("docID","fieldName")}]]></xp:this.value>
</xp:text>

Answer 1

您现在可以使用作用域 bean 很好地做到这一点，但需要注意的是 bean 是特定于 NSF 的。尽管我相信 XSP Starter kit 包含了一个关于如何做服务器作用域 bean 的例子(这实际上是一个单例，意味着整个 JVM 只有一个类的实例)。

首先创建一个名为 CachedData 的简单可序列化 POJO，它有两个成员字段，第一个是保存日期时间值的字段，该值指示您上次从磁盘读取数据的时间，第二个是某种列表对象，如向量，这就是你的值(value)观。

然后创建另一个名为 ServerMap 的 POJO，它有一个 map >>> 作为成员，以及一个名为 doCachedLookup() 或类似的函数。该函数的参数几乎可以与@DbLookup、服务器、数据库、 View 、键等相同。然后在doCachedLookup 中，检查您的ServerMap 是否存在指定的服务器作为键。如果它不存在，则创建一个新映射并将其插入到 ServerMap 中，键是服务器名称。如果确实存在，则在该映射中查找数据库名称，然后在下一个映射中查找 View ，最后在最后一个映射中查找值。拿到CachedData对象后，可以查看日期时间字段是否过期，如果没有，返回vector，如果是，丢弃，然后重新查找，重新缓存数据，然后返回向量。

这是代码示例，我在获取列与获取字段名称的重载方法中有点懒惰，并且我使用了一些不推荐使用的 Java 日期方法，但它会给你一个很好的基础。所有代码都经过测试:

缓存数据类:

package com.ZetaOne.example;

import java.io.Serializable;
import java.util.Date;
import java.util.Vector;

public class CachedData implements Serializable {

    private static final long serialVersionUID = 1L;
    private Date updateTime;
    private Vector<Object> values;

    public Date getUpdateTime() {
        return this.updateTime;
    }

    public void setUpdateTime(Date UpdateTime) {
        updateTime = UpdateTime;
    }

    public Vector<Object> getValues() {
        return this.values;
    }

    public void setValues(Vector<Object> values) {
        this.values = values;
    }
}

CachedLookup 类作为单例实现，以便它可以在服务器范围内使用:

package com.ZetaOne.example;

import java.io.Serializable;
import java.util.Date;
import java.util.Vector;
import com.ZetaOne.example.CachedData;
import java.util.HashMap;
import java.util.Collections;
import java.util.Map;

import lotus.domino.Session;
import lotus.domino.Database;
import lotus.domino.View;
import lotus.domino.NotesException;
import lotus.domino.ViewEntryCollection;
import lotus.domino.ViewEntry;
import lotus.domino.Document;

import javax.faces.context.FacesContext;

public class CachedLookup implements Serializable {

    private static CachedLookup _instance;

    private static final long serialVersionUID = 1L;
    private Map<String, HashMap<String, HashMap<String, HashMap<Object, HashMap<Object, CachedData>>>>> cachedLookup;

    public static CachedLookup getCurrentInstance() {
        if (_instance == null) {
            _instance = new CachedLookup();
        }
        return _instance;
    }       

    private CachedLookup() {
        HashMap<String, HashMap<String, HashMap<String, HashMap<Object, HashMap<Object, CachedData>>>>> cachedLookupMap =
            new HashMap<String, HashMap<String, HashMap<String, HashMap<Object, HashMap<Object, CachedData>>>>>();
        this.cachedLookup = Collections.synchronizedMap(cachedLookupMap);
    }

    @SuppressWarnings("deprecation")
    public Vector<Object> doCachedLookup(String serverName, String filePath, String viewName, Object keyValues, int columnNumber, boolean exactMatch) {

        if (cachedLookup.containsKey(serverName)) {
            if (cachedLookup.get(serverName).containsKey(filePath)) {
                if (cachedLookup.get(serverName).get(filePath).containsKey(viewName)) {
                    if (cachedLookup.get(serverName).get(filePath).get(viewName).containsKey(keyValues)) {
                        if (cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).containsKey(columnNumber)) {
                            CachedData cache = cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).get(columnNumber);
                            if (cache.getUpdateTime().compareTo(new Date()) > 0) {
                                System.out.println("Cache Hit");
                                return cache.getValues();
                            }
                        }
                    }
                }
            }
        }

        System.out.println("Cache Miss");
        // if we drop to here, cache is either expired or not present, do the lookup.

        try {
            Session session = (Session)resolveVariable("session");
            Database db = session.getDatabase(serverName, filePath);
            View view = db.getView(viewName);
            ViewEntryCollection vc = view.getAllEntriesByKey(keyValues, exactMatch);
            ViewEntry ve, vn;
            ve = vc.getFirstEntry();
            Vector<Object> results = new Vector<Object>();
            while (ve != null) {
                results.add(ve.getColumnValues().elementAt(columnNumber));

                vn = vc.getNextEntry();
                ve.recycle();
                ve = vn;
            }

            vc.recycle();

            if (!cachedLookup.containsKey(serverName)) {
                cachedLookup.put(serverName, new HashMap<String, HashMap<String, HashMap<Object, HashMap<Object, CachedData>>>>());
            }

            if (!cachedLookup.get(serverName).containsKey(filePath)) {
                cachedLookup.get(serverName).put(filePath, new HashMap<String, HashMap<Object, HashMap<Object, CachedData>>>());
            }

            if (!cachedLookup.get(serverName).get(filePath).containsKey(viewName)) {
                cachedLookup.get(serverName).get(filePath).put(viewName, new HashMap<Object, HashMap<Object, CachedData>>());
            }

            if (!cachedLookup.get(serverName).get(filePath).get(viewName).containsKey(keyValues)) {
                cachedLookup.get(serverName).get(filePath).get(viewName).put(keyValues, new HashMap<Object, CachedData>());
            }

            CachedData cache;
            if (cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).containsKey(columnNumber)) {
                cache = cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).get(columnNumber);  
            } else {
                cache = new CachedData();
            }

            Date dt = new Date();
            dt.setHours(dt.getHours() + 1);
            cache.setUpdateTime(dt);
            cache.setValues(results);           

            cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).put(columnNumber, cache);

            view.recycle();
            db.recycle();

            return results;

        } catch (NotesException e) {
            // debug here, im lazy
            return null;
        }
    }

    public Vector<Object> doCachedLookup(String serverName, String filePath, String viewName, Object keyValues, String fieldName, boolean exactMatch) {

        if (cachedLookup.containsKey(serverName)) {
            if (cachedLookup.get(serverName).containsKey(filePath)) {
                if (cachedLookup.get(serverName).get(filePath).containsKey(viewName)) {
                    if (cachedLookup.get(serverName).get(filePath).get(viewName).containsKey(keyValues)) {
                        if (cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).containsKey(fieldName)) {
                            CachedData cache = cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).get(fieldName);
                            if (cache.getUpdateTime().compareTo(new Date()) > 0) {
                                System.out.println("Cache Hit");                                
                                return cache.getValues();
                            }
                        }
                    }
                }
            }
        }

        System.out.println("Cache Miss");           
        // if we drop to here, cache is either expired or not present, do the lookup.

        try {
            Session session = (Session)resolveVariable("session");
            Database db = session.getDatabase(serverName, filePath);
            View view = db.getView(viewName);
            ViewEntryCollection vc = view.getAllEntriesByKey(keyValues, exactMatch);
            ViewEntry ve, vn;
            ve = vc.getFirstEntry();
            Vector<Object> results = new Vector<Object>();
            while (ve != null) {
                Document doc = ve.getDocument();
                results.add(doc.getItemValue(fieldName));
                doc.recycle();

                vn = vc.getNextEntry();
                ve.recycle();
                ve = vn;
            }

            vc.recycle();

            if (!cachedLookup.containsKey(serverName)) {
                cachedLookup.put(serverName, new HashMap<String, HashMap<String, HashMap<Object, HashMap<Object, CachedData>>>>());
            }

            if (!cachedLookup.get(serverName).containsKey(filePath)) {
                cachedLookup.get(serverName).put(filePath, new HashMap<String, HashMap<Object, HashMap<Object, CachedData>>>());
            }

            if (!cachedLookup.get(serverName).get(filePath).containsKey(viewName)) {
                cachedLookup.get(serverName).get(filePath).put(viewName, new HashMap<Object, HashMap<Object, CachedData>>());
            }

            if (!cachedLookup.get(serverName).get(filePath).get(viewName).containsKey(keyValues)) {
                cachedLookup.get(serverName).get(filePath).get(viewName).put(keyValues, new HashMap<Object, CachedData>());
            }

            CachedData cache;
            if (cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).containsKey(fieldName)) {
                cache = cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).get(fieldName); 
            } else {
                cache = new CachedData();
            }

            Date dt = new Date();
            dt.setHours(dt.getHours() + 1);
            cache.setUpdateTime(dt);
            cache.setValues(results);           

            cachedLookup.get(serverName).get(filePath).get(viewName).get(keyValues).put(fieldName, cache);

            view.recycle();
            db.recycle();

            return results;

        } catch (NotesException e) {
            // debug here, im lazy
            return null;
        }
    }   

    private static Object resolveVariable(String variable) {
        return FacesContext.getCurrentInstance().getApplication()
                .getVariableResolver().resolveVariable(
                        FacesContext.getCurrentInstance(), variable);
    }   

}

关于如何在 XPage 中使用的示例:

<xp:text id="text1">
    <xp:this.value><![CDATA[#{javascript:
        com.ZetaOne.example.CachedLookup.getCurrentInstance().doCachedLookup(
            database.getServer(),
            database.getFilePath(),
            "lookup",
            "Test Category",
            "Value",
            true
        )
    }]]></xp:this.value>
</xp:text>