参考

ライブラリのダウンロードURL

https://mvnrepository.com/artifact/com.google.zxing/core/3.3.0
https://mvnrepository.com/artifact/com.google.zxing/javase/3.3.0

手順

core-3.3.0.jarとjavase-3.3.0.jarをWebContent/WEB-INF/libに置く
以下のServletとJSPを作成(JSP側から実行)

qrCode.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>QRコード表示</title>
</head>
<body>
<h1>QRコード表示</h1>
<%-- <img>タグのsrc属性にQRコード描画サーブレットを指定 --%>
<img style="width: 100px; height: 100px" src="QRcodeGenerator">
</body>
</html>

QRcodeGenerator.java



import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.concurrent.ConcurrentHashMap;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.WriterException;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

/**
 * Servlet implementation class Qrcode
 */
@WebServlet("/QRcodeGenerator")
public class QRcodeGenerator extends HttpServlet {
    private static final long serialVersionUID = 1L;


    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //QRコード生成したい文字列の設定
        String source = "★★★";
        //QRコード生成時のエンコーディング
        String encoding = "UTF-8";
        //サイズ(ピクセル)
        int size = 100;

        //生成処理
        ConcurrentHashMap hints = new ConcurrentHashMap();
        //エラー訂正レベル指定
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.M);
        //エンコーディング指定
        hints.put(EncodeHintType.CHARACTER_SET, encoding);
        //マージン指定
        hints.put(EncodeHintType.MARGIN, 0);
        QRCodeWriter writer = new QRCodeWriter();
        BitMatrix bitMatrix;
        try {
            bitMatrix = writer.encode(source, BarcodeFormat.QR_CODE, size, size, hints);
            BufferedImage image = MatrixToImageWriter.toBufferedImage(bitMatrix);
            // 画像をクライアントに返却する
            response.setContentType("image/png");
            OutputStream os = response.getOutputStream();
            ImageIO.write(image, "png", os);
            os.flush();
        } catch (WriterException e) {
            e.printStackTrace();
        }

    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

QRコードメモ

参考

ライブラリのダウンロードURL

手順