[feat] 增加读取大文件（csv）

src/main/java/com/yexuejc/base/annotation/CsvHeader.java

@@ -0,0 +1,21 @@
+package com.yexuejc.base.annotation;
+
+import java.lang.annotation.*;
+
+/**
+ * 设置csv header
+ *
+ * @author MAXF-MAC
+ */
+@Target({ElementType.TYPE})
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Inherited
+public @interface CsvHeader {
+
+    /**
+     * 在类头上设置csv格式的header
+     * @return
+     */
+    String header();
+}

src/main/java/com/yexuejc/base/annotation/ToUeProperty.java

@@ -1,4 +1,6 @@
-package com.yexuejc.base.util;
+package com.yexuejc.base.annotation;
+
+import com.yexuejc.base.util.ObjUtil;
 
 import java.lang.annotation.*;
 

src/main/java/com/yexuejc/base/pojo/ReadFileBean.java

@@ -0,0 +1,85 @@
+package com.yexuejc.base.pojo;
+
+import java.util.List;
+
+/**
+ * @author maxf
+ * @class-name ReadFileBean
+ * @description 分段读取大文件
+ * @date 2022/5/16 21:53
+ */
+public class ReadFileBean<T> {
+    /**
+     * 开始行数
+     */
+    private int startRowNum;
+    /**
+     * 结束行数
+     */
+    private int endRowNum;
+
+    /**
+     * 每次读取的行数
+     */
+    private int readRowNum;
+    /**
+     * 开始行到结束行的数据
+     */
+    private List<T> datas;
+    /**
+     * 文件指针位置,默认0，开始位置
+     */
+    private long pointer = 0;
+    /**
+     * 文件的length
+     */
+    private long fileLength;
+
+
+    public ReadFileBean(int readRow) {
+        this.readRowNum = readRow;
+        this.startRowNum = 1;
+        this.endRowNum = 0;
+    }
+
+    public int getReadRowNum() {
+        return readRowNum;
+    }
+
+    public int getStartRowNum() {
+        return startRowNum;
+    }
+
+    public int getEndRowNum() {
+        return endRowNum;
+    }
+
+    public List<T> getDatas() {
+        return datas;
+    }
+
+    public ReadFileBean<T> setDatas(List<T> datas) {
+        this.datas = datas;
+        this.startRowNum = this.endRowNum + 1;
+        this.endRowNum += this.readRowNum;
+        return this;
+    }
+
+    public long getPointer() {
+        return pointer;
+    }
+
+    public ReadFileBean<T> setPointer(long pointer) {
+        this.pointer = pointer;
+        return this;
+    }
+
+    public long getFileLength() {
+        return fileLength;
+    }
+
+    public ReadFileBean<T> setFileLength(long fileLength) {
+        this.fileLength = fileLength;
+        return this;
+    }
+}

src/main/java/com/yexuejc/base/util/FileUtil.java

@@ -1,12 +1,21 @@
 package com.yexuejc.base.util;
 
+import com.yexuejc.base.annotation.CsvHeader;
+import com.yexuejc.base.pojo.ReadFileBean;
+import io.jsonwebtoken.lang.Assert;
+
 import java.io.*;
 import java.math.BigInteger;
 import java.nio.MappedByteBuffer;
 import java.nio.channels.FileChannel;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
+import java.util.ArrayList;
 import java.util.Base64;
+import java.util.Collection;
+import java.util.List;
 import java.util.logging.Logger;
 import java.util.zip.CRC32;
 
@@ -25,6 +34,7 @@ public class FileUtil {
     }
 
     private static final String TYPE_TAR_GZ = ".tar.gz";
+    private static final String TYPE_CSV = ".csv";
     private static final String TAR_GZ = "tar.gz";
 
     /**
@@ -49,7 +59,7 @@ public class FileUtil {
     }
 
     /**
-     * 判断文件是否存在
+     * 判断文件是否存在,不存在就创建一个空的
      *
      * @param file
      */
@@ -405,6 +415,92 @@ public class FileUtil {
         return 0;
     }
 
+    /**
+     * 字符串（csv格式）转 对象
+     *
+     * @param datas 转换的字符串 如
+     *              <p> ------------ </p>
+     *              <p> id,name,age </p>
+     *              <p> 1,zhangsan,18   </p>
+     *              <p> 2,lisi,20 </p>
+     *              <p> ------------ </p>
+     * @param cls   需要转换的对象,含有<b>id,name,age</b>字段
+     * @param <I>
+     * @return
+     */
+    public static <I> List readCsv(String datas, Class<I> cls) {
+
+        return null;
+    }
+
+    /**
+     * 分段读取大文件
+     *
+     * @param path         文件路径
+     * @param readFileBean 分段每次读取的bean 初始值需要设置每次读取的行数
+     * @param <T>          读取结果类型bean
+     * @return
+     */
+    public <T> ReadFileBean<T> readBigFile(String path, ReadFileBean<T> readFileBean, Class<T> readCls) {
+        File file = new File(path);
+        judeFileExists(file);
+        try {
+            RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r");
+            randomAccessFile.seek(readFileBean.getPointer());
+            readFileBean.setFileLength(randomAccessFile.length());
+            List<String> datas = new ArrayList<>();
+            for (int i = 0; i < readFileBean.getReadRowNum(); i++) {
+                String s = randomAccessFile.readLine();
+                datas.add(charsetDecode(s, StandardCharsets.UTF_8));
+                readFileBean.setPointer(randomAccessFile.getFilePointer());
+            }
+            randomAccessFile.close();
+            if (path.contains(TYPE_CSV)) {
+                //csv文件处理
+                datas.add(0, getCsvHeader(readCls));
+                List<T> dataList = readCsv(String.join("\n", datas), readCls);
+                readFileBean.setDatas(dataList);
+            }
+        } catch (FileNotFoundException e) {
+            logger.severe("file exists." + e.getMessage());
+        } catch (IOException e) {
+            logger.severe("read file error." + e.getMessage());
+        }
+        return readFileBean;
+    }
+
+    /**
+     * 获取csv的header,使用注解{@link CsvHeader}
+     *
+     * @param cls
+     * @param <T>
+     * @return
+     */
+    public static <T> String getCsvHeader(Class<T> cls) {
+        CsvHeader annotation = cls.getAnnotation(CsvHeader.class);
+        Assert.notNull(annotation, cls.toString() + "类上需要添加注解@CsvHeader，并指定header。");
+        String header = annotation.header();
+        Assert.notNull(header, cls.toString() + "类上需要添加注解@CsvHeader，并指定header。");
+        return header;
+    }
+
+    /**
+     * 把字符串data按照指定编码解码
+     *
+     * @param data    解码字符串
+     * @param charset 字符编码
+     * @return
+     */
+    public static String charsetDecode(String data, Charset charset) {
+        char[] chars = data.toCharArray();
+        byte[] result = new byte[chars.length];
+        for (int i = 0; i < chars.length; i++) {
+            result[i] = (byte) chars[i];
+        }
+        return new String(result, charset);
+    }
+
+
     /*public static void main(String[] args) {
         long size = FileUtil.size(new File("E:\\OS\\deepin-15.6-amd64\\DeepinCloudPrintServerInstaller_1.0.0.1.exe"));
         System.out.println(size);

src/main/java/com/yexuejc/base/util/ObjUtil.java

@@ -1,5 +1,7 @@
 package com.yexuejc.base.util;
 
+import com.yexuejc.base.annotation.ToUeProperty;
+
 import java.io.*;
 import java.lang.reflect.Field;
 import java.time.LocalDate;

src/test/java/com/yexuejc/base/util/ObjUtilTest.java

@@ -1,5 +1,7 @@
 package com.yexuejc.base.util;
 
+import com.yexuejc.base.annotation.ToUeProperty;
+
 import java.io.Serializable;
 import java.math.BigDecimal;
 import java.time.LocalDateTime;