应用程序开箱即用的对象持久性计划

样例源代码

清单 1 展示了 StockData 程序的源代码：

清单 1. StockData

public class StockData{ private static Log log; public static void main(String[] args) { tProperty(\"nfiguration\", \"file:operties\"); log = tLog(ass); try { String symbol = args[0]; String csvFile = args[1]; String query = args[2]; // open store, uses HSQLDB driver and memory only database Store store = new Store(\"bcDriver\",\"jdbc:hsqldb:mem:stockdata\"); // read csv and generate beans List historicalData = adLines(new File(csvFile), \"UTF-8\"); // remove first line (header) move(0); // store beans to database for (Object _data : historicalData) { String[] data = ((String) _data).split(\",\"); StockBean bean = new StockBean(symbol, data[0], rseDouble(data[4]), rseDouble(data[5])); //save stock bean to database ve(bean); } // find beans that match query List results=nd(query); // print beans that matched intln(\"Total results: \"+ze()); for (Object object : results) { StockBean bean=(StockBean)object; intln(String()); } } catch (Exception e) { ror(tMessage(), e); t .println(\"Usage: java ockData \" + \"symbol name historical prices file query\"); } }}

StockData 应用程序使用 Apache Commons IO 包将 CSV 文件读入 List。然后，for 循环解析文本行并创建 StockBean 对象，该对象被存入数据库中。CSV 文件的格式如下：

Date,Open,High,Low,Close,Volume,Adj. Close*

29-Dec-06,97.00,97.88,96.83,97.15,,97.15

两度请辞 行政院长 与远走金门 28-Dec-06,97.11,97.40,96.87,96.97,,96.97

27-Dec-06,96.30,97.23,96.27,97.20,,97.20

可下载演示包 中提供了一个样例 CSV 文件。

将所有对象存入数据库后，会执行一个简单的 find 查询（在命令行中指定）并返回一份相匹配结果的 List。结果打印到 t。请注意，Simple Persistence for Java 实现 LazyList，对象可在 LazyList 中随需检索。这确保了内存中最终不会出现成千上万的对象。

StockBean 对象

清单 2 展示了 StockBean Java 对象的源代码，该代码用于存储 StockData 中的信息。StockBean 有四个字段：symbol name、date、price 和 volume。

清单 2. StockBean 对象

public class StockBean{ private String symbolName = \"\"; private String date = null; private double price = 0.0; private double volume = 0.0; public StockBean() { // no-argument constructor required by Simple Persistence } public String toString() { StringBuffer sb=new StringBuffer(); pend(symbolName); pend(\',\'); pend(date); pend(\',\'); pend(price); pend(\',\'); pend(volume); return String(); } public StockBean(String symbolName, String date, double price, double volume) { mbolName = symbolName; te = date; ice = price; lume = volume; } public String getDate() { return date; } public void setDate(String date) { te = date; } public double getPrice() { return price; } public void setPrice(double price) { ice = price; } public String getSymbolName() { return symbolName; } public void setSymbolName(String symbolName) { mbolName = symbolName; } public double getVolume() { return volume; } public void setVolume(double volume) { lume = volume; }}

查看本文来源