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java快速读取日志文件最后一行数据，日志文件非常大。
package cn.com.songjy.test.io;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
/**
* 从最后一行开始读取
*/
public class FromEndRF {
/**
*
* @param filename 目标文件
* @param charset 目标文件的编码格式
*/
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) {// 当文件指针退至文件开始处，输出第一行
// 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");
}
}
说明：以上是一个倒着读取文件的案例，可以根据此案例，结合自己的实际需求来设计自己的代码。另外，如果是web应用或其它持续型应用，可以尝试利用单独线程保持文件打开或将读取位置存储在内存中。
java怎么读取windows 事件日志 文件
您好，很高兴为您解答。日志文件在哪个目录，用fileinputstream读文件就行了
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定时读取日志文件
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");
// 移动文件指针到上次读的最后
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+"次读到的内容:");
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("写入的内容").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该如何使用日志文件
java使用日志文件log4j的方法：
1、 新建一个Java工程，导入Log4j包，pom文件中对应的配置代码如下：
!-- log4j support --
dependency
groupIdlog4j/groupId
artifactIdlog4j/artifactId
version1.2.17/version
/dependency
2、resources目录下创建log4j.properties文件
### 设置###
log4j.rootLogger = debug,stdout,D,E
### 输出信息到控制抬 ###
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
### 输出DEBUG 级别以上的日志到=/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
### 输出ERROR 级别以上的日志到=/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、输出日志的例子如下
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) {
// 记录debug级别的信息
logger.debug("This is debug message.");
// 记录info级别的信息
logger.info("This is info message.");
// 记录error级别的信息
logger.error("This is error message.");
}
}
4、输出结果
首先，控制台输入如下图所示：
然后，查看/Users/duqi/logs目录下的debug.log和error.log文件，内容分别如下，可以看出：
