java编写ftp下载工具
投稿：hebedich
本文给大家介绍的是如何一步步实现使用java编写FTP下载工具，而且是在Linux环境下使用javac编译的，在运行和编译上有些不同之处，有需要的小伙伴们参考下吧。
需要用到 java 写一个 ftp 的工具，因为只有一点点 java 基础，但是由于好几年不用，几乎算是不会了，只好一点点来搞，还好能捡起来。
不过因为是在 Linux 下使用 javac 编译，不是在 WIN 下使用 IDE 来做这些事情，所以在运行和编译上又费了一些时间，不过正是因为这样对 JAVA 的一些编译、运行的知识又了解了一些。
对于 ftp 下载工具，代码如下：
复制代码 代码如下:
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.SocketException;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPReply;
public class FtpClient {
private String host;
private int port;
private String username;
private String password;
private boolean binaryTransfer = true;
private boolean passiveMode = true;
private String encoding = "UTF-8";
private int clientTimeout = 3000;
private boolean flag=true;
private FTPClient ftpClient = null;
public String getHost() {
return host;
}
public void setHost(String host) {
this.host = host;
}
public int getPort() {
return port;
}
public void setPort(int port) {
this.port = port;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public boolean isBinaryTransfer() {
return binaryTransfer;
}
public void setBinaryTransfer(boolean binaryTransfer) {
this.binaryTransfer = binaryTransfer;
}
public boolean isPassiveMode() {
return passiveMode;
}
public void setPassiveMode(boolean passiveMode) {
this.passiveMode = passiveMode;
}
public String getEncoding() {
return encoding;
}
public void setEncoding(String encoding) {
this.encoding = encoding;
}
public int getClientTimeout() {
return clientTimeout;
}
public void setClientTimeout(int clientTimeout) {
this.clientTimeout = clientTimeout;
}
public FtpClient(String Host) {
this.username = "anonymous";
this.encoding = "utf-8";
this.binaryTransfer = true;
this.binaryTransfer = true;
this.port = 21;
this.host = Host;
try {
this.ftpClient = getFTPClient();
} catch (Exception e) {
System.out.println("Create FTPClient error!");
}
}
private FTPClient getFTPClient() throws IOException {
FTPClient ftpClient = new FTPClient();
ftpClient.setControlEncoding(encoding);
connect(ftpClient);
if (passiveMode) {
ftpClient.enterLocalPassiveMode();
}
setFileType(ftpClient);
try {
ftpClient.setSoTimeout(clientTimeout);
} catch (SocketException e) {
throw new IOException("Set timeout error.", e);
}
return ftpClient;
}
private void setFileType(FTPClient ftpClient) throws IOException {
try {
if (binaryTransfer) {
ftpClient.setFileType(FTPClient.BINARY_FILE_TYPE);
} else {
ftpClient.setFileType(FTPClient.ASCII_FILE_TYPE);
}
} catch (IOException e) {
throw new IOException("Could not to set file type.", e);
}
}
public boolean connect(FTPClient ftpClient) throws IOException {
try {
ftpClient.connect(host, port);
int reply = ftpClient.getReplyCode();
if (FTPReply.isPositiveCompletion(reply)) {
if (ftpClient.login(username, password)) {
setFileType(ftpClient);
return true;
}
} else {
this.ftpClient.disconnect();
throw new IOException("FTP server refused connection.");
}
} catch (IOException e) {
if (this.ftpClient.isConnected()) {
try {
this.ftpClient.disconnect();
} catch (IOException e1) {
throw new IOException("Could not disconnect from server.", e);
}
}
throw new IOException("Could not connect to server.", e);
}
return false;
}
private void disconnect() throws IOException {
try {
this.ftpClient.logout();
} catch (IOException e) {
System.out.println("logout may timeout!");
} finally {
if (this.ftpClient.isConnected()) {
this.ftpClient.disconnect();
}
}
}
public InputStream getStream(String serverFile) throws IOException {
InputStream inStream = null;
try {
inStream = this.ftpClient.retrieveFileStream(serverFile);
System.out.println("inStream get over!");
return inStream;
} catch (IOException e) {
System.out.println("get stream exception");
return null;
}
}
public boolean writeStream(InputStream input, String localFile) throws IOException {
FileOutputStream fout = new FileOutputStream(localFile);
int ch = 0;
if(input == null){
System.out.println("input is null");
return false;
}
try {
ch = input.read();
while(ch != -1){
fout.write(ch);
ch = input.read();
}
System.out.println("write over!");
return flag;
} catch (IOException e) {
throw new IOException("Couldn't get file from server.", e);
}
}
public boolean isExist(String remoteFilePath)throws IOException{
try{
File file=new File(remoteFilePath);
String remotePath=remoteFilePath.substring(0,(remoteFilePath.indexOf(file.getName())-1));
String[] listNames = this.ftpClient.listNames(remotePath);
System.out.println(remoteFilePath);
for(int i=0;i<listNames.length;i++){
System.out.println(listNames[i]);
if(remoteFilePath.equals(listNames[i])){
flag=true;
System.out.println("file:"+file.getName()+" existed");
break;
}else {
flag=false;
}
}
} catch (IOException e) {
throw new IOException("FILE EXCEPTION", e);
}
return flag;
}
//main for testing
public static void main(String[] args) throws IOException {
String hostname = "cp01-testing-ps7130.cp01.baidu.com";
String serverFile="/home/work/check_disk.sh";
String localFile="/home/work/workspace/project/dhc2-0/dhc/base/ftp/task_get";
FtpClient ftp = new FtpClient(hostname);
System.out.println(ftp.isExist(serverFile));
ftp.writeStream(ftp.getStream(serverFile), localFile);
ftp.disconnect();
}
}
这个工具是为了配合另外一个 Hadoop 工具做 集群上传用的，所以里面的把 input 和 output 流分开了，也是为了方便另外一个工具使用。
补充一点，如何在 linux 配置运行：
如果这样的代码需要在 linux 下环境运行，首先要配置好响应的包，例如
复制代码 代码如下:
import org.apache.commons.net.ftp.FTPClient;
这个包在 apache 的网站上直接下载就行，解压后找到对应的 jar 包，在编译的时候进行引用：
复制代码 代码如下:
export FTPPATH="${路径}/xxx.jar"
javac -classpath $CLASSPATH:$FTPPATH FtpClient.java
同样，在运行的时候也要指定 classpath：
复制代码 代码如下:
java -classpath $CLASSPATH:$FTPPATH FtpClient
建议不要把$FTPPATH 包含在 CLASSPATH 中，用什么包就引用什么环境变量就行了，没必要一股脑都添加进去，就像我们没必要 import 所有的包一样。
以上所述就是本文的全部内容了，希望能够对大家学习java有所帮助。
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