以增量的方式去适应变化

场景---图形验证码的使用

1、接口

public interface ValidateCodeGenerator {

    ImageCode createImageCode(HttpServletRequest request);

}

2、默认实现

@Data
public class ImageCodeGenerator implements ValidateCodeGenerator {

    @Autowired
    private SecurityProperties securityProperties;


    @Override
    public ImageCode createImageCode(HttpServletRequest request) {
        //从配置读取
        int width = ServletRequestUtils.getIntParameter(request, "width", securityProperties.getCode().getImage().getWidth());
        int height = ServletRequestUtils.getIntParameter(request, "height", securityProperties.getCode().getImage().getHeight());


        //step1　创建一个图片,创建一个内存映像对象
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //得到画笔
        Graphics g = image.getGraphics();
        Random r = new Random();
        //设置画笔的颜色
        g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));
        //设置整个画板的背景颜色
        g.fillRect(0, 0, width, height);
        //生成一个随机数
        //String number = r.nextInt(99999) + "";
        String number = getNumber(securityProperties.getCode().getImage().getLength());

        g.setColor(new Color(0, 0, 0));
        g.drawString(number, 5, 15);
        //加一些干扰线
        for (int i = 0; i < 4; i++) {
            g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));
            g.drawLine(r.nextInt(60), r.nextInt(20), r.nextInt(60), r.nextInt(20));
        }

        return new ImageCode(image, number, securityProperties.getCode().getImage().getExpireIn());
    }

    //随机从"A~Z","0~9"当中取出５个字符
    private String getNumber(int length) {
        Random r = new Random();
        char[] chars = {'A', 'B', 'C', 'D', 'E', 'F', 'G',
                'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q',
                'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '0',
                '1', '2', '3', '4', '5', '6', '7', '8', '9'};
        String number = "";
        for (int i = 0; i < length; i++) {
            number += chars[r.nextInt(chars.length)];
        }
        return number;
    }
}

3、配置

@Configuration
public class ValidateCodeBeanConfig {

    @Autowired
    private SecurityProperties securityProperties;


    @Bean
    @ConditionalOnMissingBean(name = "imageCodeGenerator") //在容器中去找是否有imageCOdeGenerator。如果没有就用方法内配置的bean
    public ValidateCodeGenerator imageCodeGenerator(){
        ImageCodeGenerator codeGenerator = new ImageCodeGenerator();
        codeGenerator.setSecurityProperties(securityProperties);
        return codeGenerator;
    }

}

4、使用

@RestController
public class ValidateCodeController {

    public static final String SESSION_KEY = "SESSION_IMAGE_CODE";

    private SessionStrategy sessionStrategy = new HttpSessionSessionStrategy();

    @Autowired
    private ValidateCodeGenerator imageCodeGenerator;


    @GetMapping("/code/image")
    public void createCode(HttpServletRequest request,
                           HttpServletResponse response) throws IOException {

        ImageCode imageCode = imageCodeGenerator.createImageCode(request);
        sessionStrategy.setAttribute(new ServletWebRequest(request), SESSION_KEY, imageCode);
        ImageIO.write(imageCode.getImage(), "JPEG", response.getOutputStream());
    }
}

5、增量

/**
 * 配置一个bean去覆盖默认的bean（ValidateCodeBeanConfig-》imageCodeGenerator）
 */
@Component("imageCodeGenerator")
public class DemoImageCodeGenerator implements ValidateCodeGenerator {

    @Override
    public ImageCode createImageCode(HttpServletRequest request) {
        System.out.println("更高级的图形验证码生成代码");
        return null;
    }
}