java - 从文件中读取内容并发送电子邮件

Question

我在从文件中读取内容并将其作为 java 中的电子邮件正文发送时遇到了麻烦。但是，如果我运行代码来发送电子邮件而不从文件中读取内容，它会成功发送电子邮件，但在从文件中读取正文内容时会出现问题。如果您能帮助我，那就太好了，下面是我正在使用的代码

提前致谢!

package com.example.tests;

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;

public class sendEmail {

    private static String USER_NAME = "zxxzz@gmail.com";  // GMail user name (just the part before "@gmail.com")
    private static String PASSWORD = "xxxxxxx"; // GMail password
    private static String RECIPIENT = "zxxzz@gmail.com";
    static String strLine = null;
    public static void main(String[] args) {
        String from = USER_NAME;
        String pass = PASSWORD;
        String[] to = { RECIPIENT }; // list of recipient email addresses
        String subject = "Java send mail example";
        String body = strLine;

        readfile();
        sendFromGMail(from, pass, to, subject, body);
    }

    private static void sendFromGMail(String from, String pass, String[] to, String subject, String body) {
        Properties props = System.getProperties();
        String host = "smtp.gmail.com";
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", host);
        props.put("mail.smtp.user", from);
        props.put("mail.smtp.password", pass);
        props.put("mail.smtp.port", "587");
        props.put("mail.smtp.auth", "true");

        Session session = Session.getDefaultInstance(props);
        MimeMessage message = new MimeMessage(session);

        try {
            message.setFrom(new InternetAddress(from));
            InternetAddress[] toAddress = new InternetAddress[to.length];

            // To get the array of addresses
            for( int i = 0; i < to.length; i++ ) {
                toAddress[i] = new InternetAddress(to[i]);
            }

            for( int i = 0; i < toAddress.length; i++) {
                message.addRecipient(Message.RecipientType.TO, toAddress[i]);
            }

            message.setSubject(subject);
            message.setText(body);
            Transport transport = session.getTransport("smtp");
            transport.connect(host, from, pass);
            transport.sendMessage(message, message.getAllRecipients());
            transport.close();
        }
        catch (AddressException ae) {
            ae.printStackTrace();
        }
        catch (MessagingException me) {
            me.printStackTrace();
        }
    }


    public static void readfile(){    
        try{
            // Open the file that is the first 
            // command line parameter
            FileInputStream fstream = new FileInputStream("C:\\Sample.txt");
            // Get the object of DataInputStream
            DataInputStream in = new DataInputStream(fstream);
            BufferedReader br = new BufferedReader(new InputStreamReader(in));

            //Read File Line By Line
            while ((strLine = br.readLine()) != null)   {
                // Print the content on the console
                System.out.println (strLine);
            }
            //Close the input stream
            in.close();
        }catch (Exception e){//Catch exception if any
            System.err.println("Error: " + e.getMessage());
        }
    }
}

我得到的异常:

          Exception in thread "main" java.lang.NullPointerException
        at org.apache.geronimo.mail.util.ASCIIUtil.isAscii(ASCIIUtil.java:47)
        at javax.mail.internet.MimeMessage.setText(MimeMessage.java:939)
        at javax.mail.internet.MimeMessage.setText(MimeMessage.java:932)
        at com.example.tests.sendEmail.sendFromGMail(sendEmail.java:55)
        at com.example.tests.sendEmail.main(sendEmail.java:25)

Answer 1

strLine 为空!

您正在正确读取文件，但循环该文件时最后一个分配将为空

strLine = br.readLine()) != null

也许是一个疏忽。

替换

        //Read File Line By Line
        while ((strLine = br.readLine()) != null)   {
            // Print the content on the console
            System.out.println (strLine);
        }

至

        //Read File Line By Line
        String line;
        strLine="";
        while ((line = br.readLine()) != null)   {
            // Print the content on the console
            strLine += line;
        }
        System.out.println (strLine);

或者更好地使用string buffer

        //Read File Line By Line
        String line;
        StringBuffer buffer = new StringBuffer("");
        while ((line = br.readLine()) != null)   {
            // Print the content on the console
            buffer.append(line);
        }
        strLine = buffer .toSTring();
        System.out.println (strLine);

然后调用

sendFromGMail(from, pass, to, subject, strLine);