通过java读取classpath下的properties配置文件内容，如下“代码段一”；此时，命令行通过
java -classpath ./testClasspath.jar:./test.properties com.devin.TestClasspath指定外部的classpath，代码依然能读取test.properties的配置内容, test.properties可以放到任意位置，只要在-classpath指定该路径就可以
Springboot jar包运行模式：
假设此时springboot的工程依赖上面提到的testClasspath.jar包，需要把springboot打成jar包，通过java -jar springboot.jar的方式启动服务；但springboot不支持设置-classpath，所以无法为testClasspath.jar指定外部test.properties文件的路径
问题是：springboot是否有什么方式可以设置外部目录成为classpath，让其依赖的其它jar包能读取到classpath下的配置文件？
之所以有这个问题，是因为有些配置文件不是springboot项目维护的（比如YARN的core-site.xml）,只能通过指定classpath的方式为hadoop的jar包读取文件的目录
代码段一：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;
import java.util.Set;
public class TestClasspath{
private static String keyValueSeparators = "=: \t\r\n\f";
private static String strictKeyValueSeparators = "=:";
private static String specialSaveChars = "=: \t\r\n\f#!";
private static String whiteSpaceChars = " \t\r\n\f";
public static void main(String[] args){
try
{
InputStream is = TestClasspath.class.getClassLoader().getResourceAsStream("test.properties");
Properties testProperties = new Properties();
load(testProperties, is, "utf-8");
Set<Entry<Object, Object>> propertiesSet = testProperties.entrySet();
for (Map.Entry<Object, Object> entry : propertiesSet)
{
String sparkConfKey = entry.getKey().toString();
String sparkConfValue = entry.getValue().toString();
System.out.println(sparkConfKey + " = " + sparkConfValue);
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
public static void load(Properties properties, InputStream inStream, String encoding)
throws IOException
{
InputStreamReader reader = new InputStreamReader(inStream, encoding);
load(properties, reader);
}
public static void load(Properties properties, Reader reader) throws IOException
{
BufferedReader in = new BufferedReader(reader);
while (true)
{
// Get next line
String line = in.readLine();
if (line == null)
{
return;
}
if (line.length() > 0)
{
// Find start of key
int len = line.length();
int keyStart;
for (keyStart = 0; keyStart < len; keyStart++)
{
if (whiteSpaceChars.indexOf(line.charAt(keyStart)) == -1)
{
break;
}
}
// Blank lines are ignored
if (keyStart == len)
{
continue;
}
// Continue lines that end in slashes if they are not comments
char firstChar = line.charAt(keyStart);
if ((firstChar != '#') && (firstChar != '!'))
{
while (continueLine(line))
{
String nextLine = in.readLine();
if (nextLine == null)
{
nextLine = "";
}
String loppedLine = line.substring(0, len - 1);
// Advance beyond whitespace on new line
int startIndex;
for (startIndex = 0; startIndex < nextLine.length(); startIndex++)
{
if (whiteSpaceChars.indexOf(nextLine.charAt(startIndex)) == -1)
{
break;
}
}
nextLine = nextLine.substring(startIndex, nextLine.length());
line = new String(loppedLine + nextLine);
len = line.length();
}
// Find separation between key and value
int separatorIndex;
for (separatorIndex = keyStart; separatorIndex < len; separatorIndex++)
{
char currentChar = line.charAt(separatorIndex);
if (currentChar == '\\')
{
separatorIndex++;
}
else if (keyValueSeparators.indexOf(currentChar) != -1)
{
break;
}
}
// Skip over whitespace after key if any
// test
int valueIndex;
for (valueIndex = separatorIndex; valueIndex < len; valueIndex++)
{
if (whiteSpaceChars.indexOf(line.charAt(valueIndex)) == -1)
{
break;
}
}
// Skip over one non whitespace key value separators if any
if (valueIndex < len)
{
if (strictKeyValueSeparators.indexOf(line.charAt(valueIndex)) != -1)
{
valueIndex++;
}
}
// Skip over white space after other separators if any
while (valueIndex < len)
{
if (whiteSpaceChars.indexOf(line.charAt(valueIndex)) == -1)
{
break;
}
valueIndex++;
}
String key = line.substring(keyStart, separatorIndex);
String value = (separatorIndex < len) ? line.substring(valueIndex, len) : "";
// Convert then store key and value
key = loadConvert(key);
value = loadConvert(value);
properties.put(key, value);
}
}
}
}
private static boolean continueLine(String line)
{
int slashCount = 0;
int index = line.length() - 1;
while ((index >= 0) && (line.charAt(index--) == '\\'))
{
slashCount++;
}
return ((slashCount % 2) != 0);
}
private static String loadConvert(String theString)
{
char aChar;
int len = theString.length();
StringBuffer outBuffer = new StringBuffer(len);
for (int x = 0; x < len; )
{
aChar = theString.charAt(x++);
if (aChar == '\\')
{
aChar = theString.charAt(x++);
if (aChar == 'u')
{
// Read the xxxx
int value = 0;
for (int i = 0; i < 4; i++)
{
aChar = theString.charAt(x++);
switch (aChar)
{
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
value = ((value << 4) + aChar) - '0';
break;
case 'a':
case 'b':
case 'c':
case 'd':
case 'e':
case 'f':
value = ((value << 4) + 10 + aChar) - 'a';
break;
case 'A':
case 'B':
case 'C':
case 'D':
case 'E':
case 'F':
value = ((value << 4) + 10 + aChar) - 'A';
break;
default:
throw new IllegalArgumentException("Malformed \\uxxxx encoding.");
}
}
outBuffer.append((char) value);
}
else
{
if (aChar == 't')
{
aChar = '\t';
}
else if (aChar == 'r')
{
aChar = '\r';
}
else if (aChar == 'n')
{
aChar = '\n';
}
else if (aChar == 'f')
{
aChar = '\f';
}
outBuffer.append(aChar);
}
}
else
{
outBuffer.append(aChar);
}
}
return outBuffer.toString();
}
}
