本文目錄一覽：
java快速讀取日誌文件最後一行數據，日誌文件非常大。
package cn.com.songjy.test.io;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
/**
* 從最後一行開始讀取
*/
public class FromEndRF {
/**
*
* @param filename 目標文件
* @param charset 目標文件的編碼格式
*/
public static void read(String filename, String charset) {
RandomAccessFile rf = null;
try {
rf = new RandomAccessFile(filename, “r”);
long len = rf.length();
long start = rf.getFilePointer();
long nextend = start + len – 1;
String line;
rf.seek(nextend);
int c = -1;
while (nextend start) {
c = rf.read();
if (c == ‘\n’ || c == ‘\r’) {
line = rf.readLine();
if (line != null) {
System.out.println(new String(line
.getBytes(“ISO-8859-1”), charset));
} else {
System.out.println(line);
}
nextend–;
}
nextend–;
rf.seek(nextend);
if (nextend == 0) {// 當文件指針退至文件開始處，輸出第一行
// System.out.println(rf.readLine());
System.out.println(new String(rf.readLine().getBytes(
“ISO-8859-1”), charset));
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (rf != null)
rf.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public static void main(String args[]) {
read(“mynewfile.txt”, “UTF-8”);
}
}
說明：以上是一個倒著讀取文件的案例，可以根據此案例，結合自己的實際需求來設計自己的代碼。另外，如果是web應用或其它持續型應用，可以嘗試利用單獨線程保持文件打開或將讀取位置存儲在內存中。
java怎麼讀取windows 事件日誌 文件
您好，很高興為您解答。日誌文件在哪個目錄，用fileinputstream讀文件就行了
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
public class FileReaderTest {
static ListString logs = new ArrayListString();
public static ListString readFile(File f) throws IOException {
if (f == null || !f.exists()) {
return null;
}
ListString list = new ArrayListString();
String encoding = “UTF-8”;
InputStreamReader read = new InputStreamReader(new FileInputStream(f),
encoding);
BufferedReader br = new BufferedReader(read);
String line = null;
java定時讀取日誌文件
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.RandomAccessFile;
import java.io.ByteArrayInputStream;
class Reader implements Runnable {
Reader(String filename) {
this.filename = filename;
}
private String filename;
private long filelength = 0;
private int count=0;
@Override
public void run() {
while (true) {
try {
File f = new File(filename);
long nowlength = f.length();
long readlength = nowlength – filelength;
if (readlength == 0) {
Thread.sleep(1000);
continue;
}
RandomAccessFile rf = new RandomAccessFile(f, “r”);
// 移動文件指針到上次讀的最後
rf.seek(filelength);
filelength=nowlength;
byte[] b = new byte[(int) readlength];
rf.read(b, 0, b.length);
rf.close();
BufferedReader br=new BufferedReader(new InputStreamReader(new ByteArrayInputStream(b)));
String str=null;
count++;
System.out.println(“第”+count+”次讀到的內容:”);
while((str=br.readLine())!=null){
System.out.println(str);
}
br.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
class Writer implements Runnable{
Writer(String filename) {
this.filename = filename;
}
private String filename;
private int count=0;
@Override
public void run() {
while (count++100){
try {
PrintWriter pw=new PrintWriter(new FileWriter(filename,true));
pw.append(“”+count).append(“\t”).append(“”+System.currentTimeMillis()).append(“寫入的內容”).append(“\r\n”);
pw.close();
Thread.sleep(100);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
public class ReadFileFromTrail {
public static void main(String[] args) {
Reader reader=new Reader(“d:\\test.log”);
Writer writer=new Writer(“d:\\test.log”);
new Thread(reader).start();
new Thread(writer).start();
}
}
log4j的使用,即java該如何使用日誌文件
java使用日誌文件log4j的方法：
1、 新建一個Java工程，導入Log4j包，pom文件中對應的配置代碼如下：
!– log4j support —
dependency
groupIdlog4j/groupId
artifactIdlog4j/artifactId
version1.2.17/version
/dependency
2、resources目錄下創建log4j.properties文件
### 設置###
log4j.rootLogger = debug,stdout,D,E
### 輸出信息到控制抬 ###
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern = [%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS} method:%l%n%m%n
### 輸出DEBUG 級別以上的日誌到=/home/duqi/logs/debug.log ###
log4j.appender.D = org.apache.log4j.DailyRollingFileAppender
log4j.appender.D.File = /home/duqi/logs/debug.log
log4j.appender.D.Append = true
log4j.appender.D.Threshold = DEBUG
log4j.appender.D.layout = org.apache.log4j.PatternLayout
log4j.appender.D.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss} [ %t:%r ] – [ %p ] %m%n
### 輸出ERROR 級別以上的日誌到=/home/admin/logs/error.log ###
log4j.appender.E = org.apache.log4j.DailyRollingFileAppender
log4j.appender.E.File =/home/admin/logs/error.log
log4j.appender.E.Append = true
log4j.appender.E.Threshold = ERROR
log4j.appender.E.layout = org.apache.log4j.PatternLayout
log4j.appender.E.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss} [ %t:%r ] – [ %p ] %m%n
3、輸出日誌的例子如下
package com.javadu.log;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class Log4JTest {
private static final Logger logger = LoggerFactory.getLogger(Log4JTest.class);
public static void main(String[] args) {
// 記錄debug級別的信息
logger.debug(“This is debug message.”);
// 記錄info級別的信息
logger.info(“This is info message.”);
// 記錄error級別的信息
logger.error(“This is error message.”);
}
}
4、輸出結果
首先，控制台輸入如下圖所示：
然後，查看/Users/duqi/logs目錄下的debug.log和error.log文件，內容分別如下，可以看出：
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