JDK Source Learning (9)-java.util.Properties instance and source code

1. Java.util.Properties description.

This class is mainly read property configuration file, two file types: Normal file format is key = Value;xml file.

1) Key = Value example is as follows:

public class Testproperties {public static void main (string[] args) {Properties Properties = new Properties (); FileInputStream fileinputstream;try {fileinputstream = new FileInputStream (New File ("D:/testproperties.txt"));// Properties.loadfromxml (FileInputStream);p roperties.load (FileInputStream); for (Object Pro:properties.keySet ()) { System.out.println (pro + "= =" + properties.get (PRO));}} catch (Exception e) {//TODO auto-generated catch Blocke.printstacktrace ();}}}

The configuration file is:

Name = Hellovalue = Good

The result is:

Name==hellovalue==good

2) Read the XML file with the following code:

public class Testproperties {public static void main (string[] args) {Properties Properties = new Properties (); FileInputStream fileinputstream;try {fileinputstream = new FileInputStream (New File ("D:/testproperties.xml")); Properties.loadfromxml (FileInputStream);//properties.load (FileInputStream); for (Object Pro:properties.keySet ()) { System.out.println (pro + "= =" + properties.get (PRO));}} catch (Exception e) {//TODO auto-generated catch Blocke.printstacktrace ();}}}

The configuration file is:

<?xml version= "1.0" encoding= "UTF-8"? ><! DOCTYPE Properties SYSTEM "Http://java.sun.com/dtd/properties.dtd" ><properties><comment>hi</ Comment><entry key= "foo" >bar</entry><entry key= "Fu" >baz</entry><entry key= "Feee" >baeee</entry></properties>

The result of the operation is:

Feee==baeeefu==bazfoo==bar

2. Source Code Analysis:

The class inherits from Hashtable, and the structure is Key-value, as follows:

public class Properties extends hashtable<object,object>

1) Load (InputStream) method, the main function of this method is to read the configuration file within the relevant configuration, and the information with the Key-value structure into the properties. The source code is:

  public synchronized void load (InputStream  instream)  throws ioexception {        load0 (new  linereader (instream));     } 

private void load0  (LINEREADER&NBSP;LR)  throws IOException {         char[] convtBuf = new char[1024];         int limit;        int keyLen;         int valueStart;         char c;        boolean hassep;      &NBSP;&NBSP;&NBSP;BOOLEAN&NBSP;PRECEDINGBACKSLASH;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;//1. Reading a configuration file by line , the return value is the length of the line         while  ((Limit = lr.readline ())   >= 0)  {            c = 0;             keyLen = 0;             valueStart = limit;             hasSep = false;             //system.out.println ("line=<"  + new string (lineBuf, 0, limit)  +  ">");             precedingbackslash = false;            / /1.1 traverse each character of the line to find = or: position of the symbol             while  (Keylen < limit)  {                 c = lr.lineBuf[keyLen];                 //need check if escaped.                 if  ((c ==  ' = '  | |   c ==  ': ')  && !precedingbackslash  {                     valuestart =  keyLen + 1;                     hasSep = true;                     break;                                      } else if  ( (c ==  '   '  | |  c ==  ' t '  | |   c ==  ' \f '  && !precedingbackslash)  {                     valuestart =  keyLen + 1;                     break;                 }                 if  (c ==  ' \ \ ')  {                     precedingbackslash = ! precedingbackslash;                 } else {                     precedingBackslash = false;                 }                 keyLen++;            }             while  (Valuestart < limit)  {                c  = lr.linebuf[valuestart];                 if  (c !=  '   '  && c !=  ' \ t '  &&   c !=  ' \f ')  {                     if  (!hassep &&  (c ==  ' = '  | |   c ==  ': ')  {                         hasSep = true;                     } else {                          break;                     }                 }                 valueStart++;             }            //keylen the final position before the symbol is not empty, Valuestart is the first non-empty position after the symbol             String  Key = loadconvert (LR.LINEBUF,&NBSP;0,&NBSP;KEYLEN,&NBSP;CONVTBUF);             string value = loadconvert (lr.linebuf, valuestart, limit -  VALUESTART,&NBSP;CONVTBUF);             // The parsed key and value are stored in the Hashtable             put (key,  value);         }    }

2) Store (OutputStream out, String comments) method, out for the output of the document, comments as the description of the configuration file, in Key-value as comment information, in the XML file format for < Comments> label content. The source code is as follows:

 public void store (outputstream out, string comments)          throws IOException    {         store0 (New bufferedwriter (New outputstreamwriter (out,  "8859_1")),                comments,                true);    }   &NBSP;&NBSP;PRIVATE&NBSP;VOID&NBSP;STORE0 (Bufferedwriter bw, string comments, boolean  escunicode)         throws IOException     {        if  (comments != null)  {             writecomments (bw, comments);         }         bw.write ("#"  + new date (). toString ());         bw.newline ();         synchronized  (This)  {            for   (Enumeration<?> e = keys ();  e.hasmoreelements ();)  {                 String key =  ( String) e.nextelement ();                 String val =  (String) Get (key);                 key = saveconvert (Key, true, escUnicode);                 /* no  need to escape embedded and trailing spaces for value, hence                  * pass false to flag.                  */                 val =  Saveconvert (Val, false, escunicode);                 bw.write (key +  "="  + val);                 bw.newline ();             }        }         bw.flush ();    }         private static&nBsp;void writecomments (bufferedwriter bw, string comments)          throws ioexception {        bw.write ("#");         int len = comments.length ();         int current = 0;         Int last = 0;        char[] uu = new  char[6];        uu[0] =  ' \ \ ';         uu[1] =  ' u ';        while  ( Current < len)  {            char  c = comments.charat (current);             if  (c >  ' \u00ff '  | |  c ==  ' \ n '  | |  c ==  ' \ R ')  {                 if  (last != current)                      bw.write (Comments.substring (Last,  current));                 if  (c >  ' \u00ff ')  {                     uu[2] = tohex ((c >> 12) &NBSP;&AMP;&NBSP;0XF);                     uu[3] = tohex ((c >>  8)  & 0xf );                      uu[4] = tohex (c >>  4)  &  0XF);                     uu[5] = tohex ( c        &  0XF);                     bw.write (new string (UU));                 } else {                     bw.newline ();                     if  (c ==   ' \ r '  &&                         current != len - 1 &&                          comments.charat (current + 1)  ==  ' \ n ')  {                          current++;                     }                     if  (current == len - 1 | |                           (Comments.charat (current + 1)  !=  ' # '  &&                          Comments.charat (current + 1)  !=  '! ')                          bw.write ("#");                 }                 last = current + 1;             }            current ++;        }        if  ( Last != current)             bw.write ( Comments.substring (last, current));       &nbsP; bw.newline ();     } 

JDK Source Learning (9)-java.util.Properties instance and source code