寫在前面

在日常開發或者學習spring mvc web專案中，當專案打包部署後，某些自定義配置項引數可能會需要改動。而這些配置項引數如果被寫死進專案中，或許會造成很大的麻煩。因此，有時候這些需要變動的自定義的配置項引數，便需要寫進配置檔案中。spring mvc 中有一個bean物件的概念，具體含義以及原理，各位猿友可自行腦補。
今天小編就向大家介紹一種從配置檔案中自動裝配bean物件池中物件的知識點。

專案需求

圖片上傳，上傳圖片在伺服器中上傳路徑的配置。

spring-mvc.xml 檔案bean的配置

<!--上傳檔案配置-->
    <bean id
 
="uploadConfig" class="com.qingyu.blog.util.UploadConfigFactoryBean">
        <property name="uploadPath" value="D:\image" />
        <property name="thumbDir" value="thumbs" />
        <property name="thumb" value="0.3" />
        <property name="imageFormat" value=".jpg"/>
    </bean
 
>

UploadConfigFactoryBean.java

package com.qingyu.blog.util;


import org.springframework.beans.factory.FactoryBean;

/**
 * @author longping jie
 * @name UploadConfig
 * @description the class is used to 上傳檔案的配置
 * @date 2017/11/10
 */
public class UploadConfigFactoryBean implements FactoryBean<UploadResolver> {
    //預設上傳位置
 

    private String uploadPath;
    //儲存縮圖的資料夾名
    private String thumbDir;
    //預設縮略比例
    private double thumb;
    //預設統一儲存格式
    private String imageFormat;

    public String getUploadPath() {
        return uploadPath;
    }

    public void setUploadPath(String uploadPath) {
        this.uploadPath = uploadPath;
    }

    public String getThumbDir() {
        return thumbDir;
    }

    public void setThumbDir(String thumbDir) {
        this.thumbDir = thumbDir;
    }

    public double getThumb() {
        return thumb;
    }

    public void setThumb(double thumb) {
        this.thumb = thumb;
    }

    public String getImageFormat() {
        return imageFormat;
    }

    public void setImageFormat(String imageFormat) {
        this.imageFormat = imageFormat;
    }


    @Override
    public UploadResolver getObject() throws Exception {
        UploadResolver r = new UploadResolver();
        r.uploadConfig = this;
        return r;
    }

    @Override
    public Class<?> getObjectType() {
        return UploadResolver.class;
    }

    @Override
    public boolean isSingleton() {
        return false;
    }
}

UploadResolver .java

package com.qingyu.blog.util;

import net.coobird.thumbnailator.Thumbnails;
import org.springframework.web.multipart.MultipartFile;

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.time.LocalDate;
import java.util.UUID;

/**
 * @author longping jie
 * @name UploadResolver
 * @description the class is used to 上傳圖片的工具類
 * @date 2017/11/10
 */
public class UploadResolver {
    UploadConfigFactoryBean uploadConfig;
    String dateName;

    public UploadResolver() {
        LocalDate dt = LocalDate.now();
        int year = dt.getYear();
        int month = dt.getMonthValue();
        int date = dt.getDayOfMonth();

        String monthStr = month + "";
        String dateStr = date + "";

        if (month < 10) {
            monthStr = "0" + monthStr;
        }
        if (date < 10) {
            dateStr = "0" + date;
        }
        dateName = String.format("%s-%s-%s", year, monthStr, dateStr);
    }

    /**
     * 按比例縮小圖片
     *
     * @param image 需要上傳的圖片
     * @return
     */
    public String saveThumbImage(MultipartFile image) {
        String imageName = createImageName();
        String thumbName = createThumbImageName();
        File imageFile = new File(imageName);
        File thumbFile = new File(thumbName);

        if (!imageFile.getParentFile().exists()) {
            imageFile.getParentFile().mkdirs();
            thumbFile.getParentFile().mkdirs();
        }

        try {
            image.transferTo(imageFile);
            Thumbnails.of(imageFile).scale(0.3f).toFile(thumbFile);//按比例縮小
        } catch (IOException e) {
            e.printStackTrace();
        }


        return thumbName;
    }

    /**
     * 裁剪圖片
     *
     * @param image 需要上傳的圖片物件
     * @param args  圖片裁剪引數
     * @return
     */
    public String saveThumbImage(MultipartFile image, CutImageArgs args) {
        String imageUrl = "";
        String imageName = createImageName();
        String thumbName = createThumbImageName();
        File imageFile = new File(imageName);
        File thumbFile = new File(thumbName);

        if (!imageFile.getParentFile().exists()) {
            imageFile.getParentFile().mkdirs();
            thumbFile.getParentFile().mkdirs();
        }

        try {
            image.transferTo(imageFile);
            BufferedImage buf = Thumbnails.of(imageFile).width(args.getPresentWidth()).height(args.getPresentHeight())
                    .asBufferedImage();
            Thumbnails.of(buf).sourceRegion(args.getX(), args.getY(), args.getW(), args.getH())
                    .size(args.getNeed_w(), args.getNeed_h()).toFile(thumbFile);
            imageUrl = thumbName;

        } catch (IOException e) {
            e.printStackTrace();
        }
        return imageUrl;

    }

    /**
     * 建立一個源圖片上傳的路徑名
     *
     * @return
     */
    private String createImageName() {
        String fileName = createUUIDName();
        String imageName = String.format("%s%s%s%s%s%s", uploadConfig.getUploadPath(), File.separator,
                dateName, File.separator, fileName, uploadConfig.getImageFormat());
        return imageName;
    }

    /**
     * 建立一個壓縮圖片上傳的路徑名
     *
     * @return
     */
    private String createThumbImageName() {
        String fileName = createUUIDName();
        String thumbName = String.format("%s%s%s%s%s%s%s%s", uploadConfig.getUploadPath(), File.separator,
                dateName, File.separator, uploadConfig.getThumbDir(),
                File.separator, fileName, uploadConfig.getImageFormat());

        return thumbName;
    }

    /**
     * 用uuid重新命名檔案
     *
     * @return 檔案新的名字
     */
    private String createUUIDName() {
        return UUID.randomUUID().toString().replaceAll("-", "");
    }


}

@Controller
@RequestMapping("/user")
public class UserController implements BeanFactoryAware {
    private Logger logger = LogManager.getLogger(UserController.class);
    @Autowired
    UserLoginService userLoginService;
    @Autowired
    SystemService systemService;
    @Autowired
    UploadResolver uploadResolver;

    .....中間程式碼省略


    BeanFactory beanFactory;

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.beanFactory = beanFactory;
    }