廖雪峰Java13网络编程-2Email编程-2接收Email
## 1接收Email协议类型
接收Email：收件人通过MUA软件把邮件从MDA抓取到本地计算机的过程。
1.1 POP3
从MUA到MDA使用最广泛的是协议是POP3 * Post Office Protocol version 3，建立在tcp之上的协议 * 标准端口110 * 整个会话加密，加密端口9951.2 IMAP
与POP3的区别：IMAP在本地的所有操作都会自动同步到服务器上，允许用户自己创建文件夹 * Internet Mail Access Protocol * 标准端口143 * 加密端口9932如何接收Email
- 使用Java Mail API，实现邮件的接收
- 无需关心POP3协议原理
//创建session
Session session = Session.getInstance(props, null);
//创建Store对象，代表用户在邮件服务器上的整个存储
Store store = new POP3SSLStore(session, url);
//获取Folder对象，最常用的是收件箱INBOX
Folder folder = store.getFolder("INBOX");
//获取Message：返回收件箱所有的邮件，并循环处理message对象
Message[] messages = folder.getMessages();
for(Message message:messages){
...
}
package com.feiyangedu.sample.pop3;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import javax.mail.Address;
import javax.mail.Authenticator;
import javax.mail.BodyPart;
import javax.mail.Flags;
import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.Part;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Store;
import javax.mail.URLName;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMessage.RecipientType;
import javax.mail.internet.MimeUtility;
import com.sun.mail.pop3.POP3SSLStore;
public class Pop3 {
final String popHost;
final String username;
final String password;
final boolean debug;
public Pop3(String popHost, String username, String password) {
this.popHost = popHost;
this.username = username;
this.password = password;
this.debug = true;
}
public static void main(String[] args) throws Exception {
Pop3 pop = new Pop3("pop.qq.com","123456789@qq.com","pop3授权码");//注意，不能用手机号，要用qq号
Folder folder = null;
Store store = null;
try {
store = pop.createSSLStore(); //获取到Store对象后，就可以获取Folder对象
folder = store.getFolder("INBOX");
folder.open(Folder.READ_WRITE);
System.out.println("Total messages: " + folder.getMessageCount()); //邮件数量
System.out.println("New messages: " + folder.getNewMessageCount()); //新邮件数量
System.out.println("Unread messages: " + folder.getUnreadMessageCount()); //未读邮件数量
System.out.println("Deleted messages: " + folder.getDeletedMessageCount()); //已删除的邮件数量
Message[] messages = folder.getMessages();
for (Message message : messages) {
printMessage((MimeMessage) message);
}
} finally {
if (folder != null) {
try {
folder.close(true);
} catch (MessagingException e) {
e.printStackTrace();
}
}
if (store != null) {
try {
store.close();
} catch (MessagingException e) {
e.printStackTrace();
}
}
}
}
//创建Store对象
public Store createSSLStore() throws MessagingException {
Properties props = new Properties();
props.setProperty("mail.store.protocol", "pop3");
props.setProperty("mail.pop3.port", "995"); // 主机端口号
props.setProperty("mail.pop3.host", this.popHost);// POP3主机名
// 启动SSL:
props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
props.put("mail.smtp.socketFactory.port", "995");
URLName url = new URLName("pop3", this.popHost, 995, "", this.username, this.password);
Session session = Session.getInstance(props, null);
session.setDebug(this.debug); // 显示调试信息
Store store = new POP3SSLStore(session, url);
store.connect(); //连接到服务器
return store;
}
Session createTLSStore() {
Properties props = new Properties();
props.put("mail.smtp.host", this.popHost); // POP3主机名
props.put("mail.smtp.port", "587"); // 主机端口号
props.put("mail.smtp.auth", "true"); // 是否需要用户认证
props.put("mail.smtp.starttls.enable", "true"); // 启用TLS加密
Session session = Session.getInstance(props, new Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(Pop3.this.username, Pop3.this.password);
}
});
session.setDebug(this.debug); // 显示调试信息
return session;
}
Session createInsecureStore() {
Properties props = new Properties();
props.put("mail.smtp.host", this.popHost); // POP3主机名
props.put("mail.smtp.port", "25"); // 主机端口号
props.put("mail.smtp.auth", "true"); // 是否需要用户认证
Session session = Session.getInstance(props, new Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(Pop3.this.username, Pop3.this.password);
}
});
session.setDebug(this.debug); // 显示调试信息
return session;
}
static void printMessage(MimeMessage msg) throws IOException, MessagingException {
System.out.println("--------------------");
System.out.println("Subject: " + MimeUtility.decodeText(msg.getSubject())); //邮件的主题
System.out.println("From: " + getFrom(msg)); //发件人
System.out.println("To: " + getTo(msg)); //收件人
System.out.println("Sent: " + msg.getSentDate().toString()); //发送时间
System.out.println("Seen: " + msg.getFlags().contains(Flags.Flag.SEEN)); //是否已读
System.out.println("Priority: " + getPriority(msg)); //优先级
System.out.println("Size: " + msg.getSize() / 1024 + "kb"); //邮件大小
System.out.println("Body: " + getBody(msg)); //邮件正文
System.out.println("--------------------");
System.out.println();
}
static String getFrom(MimeMessage msg) throws IOException, MessagingException {
Address[] froms = msg.getFrom();
return addressToString(froms[0]);
}
static String getTo(MimeMessage msg) throws MessagingException, IOException {
// 使用 msg.getAllRecipients() 获取所有收件人
Address[] tos = msg.getRecipients(RecipientType.TO);
List<String> list = new ArrayList<>();
for (Address to : tos) {
list.add(addressToString(to));
}
return String.join(", ", list);
}
static String addressToString(Address addr) throws IOException {
InternetAddress address = (InternetAddress) addr;
String personal = address.getPersonal();
return personal == null ? address.getAddress()
: (MimeUtility.decodeText(personal) + " <" + address.getAddress() + ">");
}
static String getPriority(MimeMessage msg) throws MessagingException {
String priority = "Normal";
String[] headers = msg.getHeader("X-Priority");
if (headers != null) {
String header = headers[0];
if ("1".equals(header) || "high".equalsIgnoreCase(header)) {
priority = "High";
} else if ("5".equals(header) || "low".equalsIgnoreCase(header)) {
priority = "Low";
}
}
return priority;
}
static String getBody(Part part) throws MessagingException, IOException {
if (part.isMimeType("text/*")) {//如果邮件的正文是text开头，是一个文本邮件或html邮件
return part.getContent().toString();
}
if (part.isMimeType("multipart/*")) { //如果是以multipart开头，那么他是一个带附件的邮件，还需要递归的把附件的内容读出来
Multipart multipart = (Multipart) part.getContent();
for (int i = 0; i < multipart.getCount(); i++) {
BodyPart bodyPart = multipart.getBodyPart(i);
String body = getBody(bodyPart);
if (!body.isEmpty()) {
return body;
}
}
}
return "";
}
}
3总结
Java接收Email：
- 用maven引入javamail依赖
- 确定POP3服务器信息：域名/端口/使用明文/SSL
- 调用相关API接收Email（无需关心底层TCP Socket连接）
- 设置debug模式可以查看通信详细内容（便于排查错误）
