有序的方式讀寫Properties檔案 —— 對java.util.Properties的改寫

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目的

前幾天，要做一個JSP讀寫Properties的模組，意在讓使用者能在web介面編輯系統配置。我很自然的用了java的Porperties工具類，讀出寫入不知多方便，但是使用者說修改一個儲存之後下次來就找不到自己的東西了（順序亂了）。於是需要做一個有序的Properties檔案讀寫類。果斷上stackoverflow，找了兩個例子（連結不記得了），兩種方式，抄下來。

方式一，LinkedProperties

package com.example.common;import java.io.IOException;import java.io.Writer;import java.util.ArrayList;import java.util.Collections;import java.util.Enumeration;import java.util.LinkedHashMap;import java.util.List;import java.util.Map;import java.util.Properties;import java.util.Set;public class LinkedProperties extends Properties {    private static final long serialVersionUID = 1L;    private Map<Object, Object> linkMap = new LinkedHashMap<Object,Object>();    @Override    public synchronized Enumeration keys() {        List<Object> keys = new ArrayList<Object>();        for (Map.Entry<Object, Object> entry : linkMap.entrySet()) {            keys.add(entry.getKey());        }        return Collections.enumeration(keys);    }    @Override    public synchronized Object put(Object key, Object value){        super.put(key, value);        return linkMap.put(key, value);    }    @Override    public synchronized boolean contains(Object value){        return linkMap.containsValue(value);    }    @Override    public boolean containsValue(Object value){        return linkMap.containsValue(value);    }    @Override    public synchronized Enumeration<Object> elements(){        throw new UnsupportedOperationException(          "Enumerations are so old-school, don‘t use them, "        + "use keySet() or entrySet() instead");    }    @Override    public Set<Map.Entry<Object, Object>> entrySet(){        return linkMap.entrySet();    }    @Override    public synchronized void clear(){        super.clear();        linkMap.clear();    }    @Override    public synchronized boolean containsKey(Object key){        return linkMap.containsKey(key);    }    public void store(Writer writer, String comments)            throws IOException    {        super.putAll(linkMap);        super.store(writer, comments);    }}

方式二，SequencedProperties

package com.example.common;import java.util.ArrayList;import java.util.Collections;import java.util.Enumeration;import java.util.List;import java.util.Map;import java.util.Properties;@SuppressWarnings({"rawtypes", "unchecked"})public class SequencedProperties extends Properties {    private static final long serialVersionUID = 1L;    private List keyList = new ArrayList();    @Override    public synchronized Enumeration keys() {        return Collections.enumeration(keyList);    }    @Override    public synchronized Object put(Object key, Object value) {        if (!containsKey(key)) {            keyList.add(key);        }        return super.put(key, value);    }    @Override    public synchronized Object remove(Object key) {        keyList.remove(key);        return super.remove(key);    }    @Override    public synchronized void putAll(Map values) {        for (Object key : values.keySet()) {            if (! containsKey(key)) {                keyList.add(key);            }        }        super.putAll(values);    }}

有序的方式讀寫Properties檔案 —— 對java.util.Properties的改寫