File accessing Functionalities using Java

 File Write:

1.using FileWriter

FileWriter writer=new FileWriter(new File(“c:desck/sangar.txt”));

writer.write(“Sangarbro”);

writer.close()

2.using BufferWriter

FileWriter writer=new FileWriter(new File(“c:dslo/list.txt”));

BufferedWriter bufWriter=new BufferedWriter(writer);

bufWriter.write(“sangar bro”);

bufWriter.close();

3.using fileOutStream

FileOutputStream stream=new FileOutPutStream(new File(“safn.txt”));

String conten=”sangar”;

stream.write(conten.getBytes());

stream.close();

File Reading:

1.Using reader:

FileReader reader=new FileReader(new File(“sangajn.txt”));

BufferedReader bufReader=new BufferedReader(reader);

String currentLine;

while((currentLine=bufReader.readLine())!=null){

sysout(currentLine);

}

bufReader.close();

config.properties File:

FileInputStream stream=new FileInputStream(new File(“smagna.txt”));

Properties property=new Properties();

property.load(stream);

String property=property.getProperty(“username”);

sysout(property);

Logging:

is the process of writing log messages during the execution of a program to a central place.

the main need for this log is if we use system.out.println it will be closed when console closed whereas log is kind of file we store once run is completed.by referring that document we can see the log messages.

Methods:
debug,warn,info,error,fatal

debug<info<warn<error<fatal

Components:

Log4j-2

1. Logger--->a class inside apache log4j dependency,

   1. it has multiple methods like debug,info,warn,error,fatal

   2. every class we have to create object, we can use their methods

2. Appender-->to write message into a file or Db

   1. JDBC appender

   2. File Appender

   3. console appendar

3. Layout

   1. pattern layout

   2. simple layout

   3. HTML layout

   4. XML layout

4. Ways to configure Log--->has to be placed this log4j2.xml file under main/resources/ package so that it will be automatically loaded.

• Multiple ways like using Json,Xml or Property file we can configure the Log file.

• Using Xml configuration:

  • <?xml version="1.0" encoding="UTF-8"?>
    <Configuration status="WARN">
    <Appenders>
    <!-- Console appender configuration -->
    <Console name="Console" target="SYSTEM_OUT">
    <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
    </Console>

        <!-- File appender configuration -->
        <File name="File" fileName="logs/app.log">
            <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss} [%t] %-5level %logger{36} - %msg%n" />
        </File>
    </Appenders>
    
    <Loggers>
        <!-- Root logger configuration -->
        <Root level="info">
            <AppenderRef ref="Console" />
            <AppenderRef ref="File" />
        </Root>
        
        <!-- Specific logger configuration -->
        <Logger name="com.example.myapp" level="debug" additivity="false">
            <AppenderRef ref="Console" />
            <AppenderRef ref="File" />
        </Logger>
    </Loggers>

    </Configuration>

Lets break up the code

1. First is the <Configuration> , this is like root

   1. <Appenders>--->we have multiple appenders like Console appender,File Appender,RollingFile Appender

      1. here we used both file and console appender

         1. inside we mentioned the Pattern Layout

   2. Loggers

      1. Setting the level in root level

Script:

private static Logger(apache.loggin.logger) logger=LogManager.getLogger(class.class);

logger.info(“sangar”);

logger.debug(“kumar”);

JSON:

Javascript object notation

In modern life,web applications developed in diffferent languages,our browser developed in Java script.

Webserver has to get our request and will respond via browser..So one language independent transmitting medium is required to communicate between the Browser and web server we are using JSON..which is most widely used as well

we are using depencency:(Simple JSON)

<!-- https://mvnrepository.com/artifact/com.googlecode.json-simple/json-simple -->
<dependency>
<groupId>com.googlecode.json-simple</groupId>
<artifactId>json-simple</artifactId>
<version>1.1.1</version>
</dependency>

JSON Create:

JSONObject obj=new JSONObject();

obj.put(“sangar”,”Another”);

JSONArray ar=new JSONArray();

ar.add(“SAngar bro”);

ar.add(“Another”);

obj.put(“Array”,ar);

FileWriter writer=new FileWriter(new File(“sangar.json”));

writer.writer(obj.toJSONString());

writer.close();

Read JSON File:

JSONParser parser=new JSONPArser();

FileReader reader=new FileReader(new File(“sangar.json”));

Object obj=parser.parse(reader);

JSONObject jsonObj=(JSONObject) obj;

sysout(jsonObj.get(“Sangar”));

JSONArray ar=(JSONArray)jsonObj.get(“Key”);

Iterator iter=ar.iterator();

while(iter.hasNext()){

sysout(iter.next());

}