package com.ljn.base;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.commons.io.IOUtils;
import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;
/**
《代码大全》-表驱动法-消息打印
问题描述：
Suppose you’re writing a routine to print messages that are stored in a file. The file
usually has about 500 messages, and each file has about 20 kinds of messages. The
messages originally come from a buoy and give water temperature, the buoy’s location, and so on.
Each of the messages has several fields, and each message starts with a header that has
an ID to let you know which of the 20 or sokinds of messages you’re dealing with.
书上对于这个问题的解法，我看得不是很明白，动手写了一下，就有了以下代码，基本达到目的：
*/
public class TableDriven2 {
private static final Map<String, Message> messageMap;
/**
* 正如书上所说，“消息表”可以硬编码到程序中；也可以定义在配置文件里，程序初始化时读取
* 定义在配置文件的优点是，消息格式变动时，不需要改动java代码；缺点是要解析配置文件
* 这里简单起见，只定义三种消息，且硬编码到程序中
*/
static {
messageMap = new HashMap<String, Message>();
Message temperature = new Message("001", "Temperature Message");
temperature.addField(new FloatField("Average Temperature"));
temperature.addField(new IntegerField("Number of Samples"));
temperature.addField(new StringField("Location"));
temperature.addField(new DayField("Time of Measurement"));
messageMap.put(temperature.getId(), temperature);
Message drift = new Message("002", "Drift Message");
drift.addField(new FloatField("Change in Latitude"));
drift.addField(new FloatField("Change in Longtitude"));
drift.addField(new DayField("Time of Measurement"));
messageMap.put("002", drift);
Message location = new Message("003", "Location Message");
location.addField(new FloatField("Latitude"));
location.addField(new FloatField("Longtitude"));
location.addField(new IntegerField("Depth"));
location.addField(new DayField("Time of Measurement"));
messageMap.put(location.getId(), location);
}
//示例代码。实际开发中，还应该考虑很多细节，例如每行前后的空格要去掉，要检查每行的数据是否合法，等等
public static void main(String[] args){
FileInputStream fs = null;
try {
fs = new FileInputStream("C:/Users/lijinnan/Desktop/message.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(fs));
String line = null;
boolean messageBegin = true;
Message message = null;
int fieldIndex = 0;
while ((line = br.readLine()) != null) {
if (messageBegin) {
String messageId = line;
message = messageMap.get(messageId);
System.out.println("#" + message.getName() + "#");
messageBegin = false;
continue;
}
if (message != null && message.getFields() != null) {
if (fieldIndex < message.getFields().size()) {
Field curField = message.getFields().get(fieldIndex++);
curField.readAndPrint(line);
}
if (fieldIndex == message.getFields().size()) {
messageBegin = true;
fieldIndex = 0;
System.out.println();
}
}
}
} catch (Exception e) {
//ignore for test
} finally {
IOUtils.closeQuietly(fs);
}
}
}
/*
定义消息字段的类型
只定义四种：FloatField IntegerField StringField DayField
当然这四种类型也可以定义为enum
*/
abstract class Field {
private String label;
public abstract void readAndPrint(String value);
public Field(String label) {
this.label = label;
}
public String getLabel() {
return label;
}
public void setLabel(String label) {
this.label = label;
}
}
class FloatField extends Field {
public FloatField(String label) {
super(label);
}
/**
* 假设浮点数输出的格式是保留两位小数点
*/
@Override
public void readAndPrint(String value) {
float val = Float.parseFloat(value);
String formattedValue = String.format("%.2f", val);
System.out.println(getLabel() + ":" + formattedValue);
}
}
class IntegerField extends Field {
public IntegerField(String label) {
super(label);
}
/**
* 假设整数的输出格式为原样输出
*/
@Override
public void readAndPrint(String value) {
System.out.println(getLabel() + ":" + value);
}
}
class StringField extends Field {
public StringField(String label) {
super(label);
}
/**
* 假设字符串的输出格式为原样输出
*/
@Override
public void readAndPrint(String value) {
System.out.println(getLabel() + ":" + value);
}
}
class DayField extends Field {
public DayField(String label) {
super(label);
}
/**
* 假设时间的输入格式是dd/MM/yyyy HH:mm:ss
* 输出格式是yyyy-MM-dd
* 时间的处理用到了joda-time
*/
@Override
public void readAndPrint(String value) {
DateTimeFormatter formatter = DateTimeFormat.forPattern("dd/MM/yyyy HH:mm:ss");
DateTime dt = formatter.parseDateTime(value);
System.out.println(getLabel() + ":" + dt.toString("yyyy-MM-dd"));
}
}
class Message {
private String id; //消息ID
private String name; //消息名
private List<Field> fields; //消息字段
public Message(String id, String name) {
this.id = id;
this.name = name;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Field> getFields() {
return Collections.unmodifiableList(fields);
}
public void addField(Field field) {
if (fields == null) {
fields = new ArrayList<Field>();
}
fields.add(field);
}
}
/*
测试数据，message.txt的内容：
001
1.111
11
East 111
01/01/2011 11:11:11
001
1.010
10
West 001
11/11/2011 11:11:11
002
2.0
2.1
02/02/2012 22:22:22
003
3.0
3.123
3000
03/03/2013 23:33:33
002
22.0
22.1
22/02/2012 22:22:22
003
30.0
30.123
3000
13/03/2013 23:33:33
程序输出：
#Temperature Message#
Average Temperature:1.11
Number of Samples:11
Location:East 111
Time of Measurement:2011-01-01
#Temperature Message#
Average Temperature:1.01
Number of Samples:10
Location:West 001
Time of Measurement:2011-11-11
#Drift Message#
Change in Latitude:2.00
Change in Longtitude:2.10
Time of Measurement:2012-02-02
#Location Message#
Latitude:3.00
Longtitude:3.12
Depth:3000
Time of Measurement:2013-03-03
#Drift Message#
Change in Latitude:22.00
Change in Longtitude:22.10
Time of Measurement:2012-02-22
#Location Message#
Latitude:30.00
Longtitude:30.12
Depth:3000
Time of Measurement:2013-03-13
*/
