解决CsvWriter：中文乱码、末尾行多一行空格(/r)、非第一列空字符串""显示null问题

一：主要内容

• 解决CsvWriter存csv，csv文件打开后中文乱码问题
• 解决CsvWriter存csv，csv文件最后一行总是多一行空行的问题
• 解决CsvWriter存csv，csv文件不是第一列的时候，想存入""即空字符串无法存入显示null的问题

二：解决问题前：需要做的事情

因为网上的CsvWrite的jar包导入到我们的工程中是class文件，针对上面的问题是无法修改源码的，但是我们又想用这个工具来操作csv，所以可以在自己的工程中首先pom引用这个jar包

 <dependency>
        <groupId>net.sourceforge.javacsv</groupId>
        <artifactId>javacsv</artifactId>
        <version>2.0</version>
 </dependency>

然后我们在自己的工程中创建一个类：CsvWriterExtend来继承CsvWriter，这样我们就能用网上CsvWriter这个jar中的方法，还能基于这个去修改代码，解决上诉的问题

public class CsvWriterExtend extends CsvWriter {}

三：优化解决CsvWriter工具存在的三个问题：中文乱码、末尾行多一行空格(/r)、非第一列空字符串""显示null问题

此处废话不多说，先上CsvWriterExtend类的代码，然后我们在代码中红色标注的地方会有说明，这段用来解决什么问题的，说明一下：CsvWriterExtend代码只是在CsvWriter类的基础上做了一些修改

 /**
  * Copyright (C), 2015-2019, XXX有限公司
  * FileName: CsvWriterExtend
  * Author:   yml
  * Date:     2019/5/17 15:42
  * Description:
  * History:
  * <author>          <time>          <version>          <desc>
  * tester           2019.5.17           1.0.0              优化CsvWriter工具
  */
 package com.test.csv.tool;

 import com.csvreader.CsvWriter;

 import java.io.*;
 import java.nio.charset.Charset;

 /**
  * @创建人 tester
  * @创建时间 2019/5/17
  * @描述 优化CsvWriter工具，解决了写入csv打开后中文乱码问题，解决了写入csv最后一行有/r换行的问题
  *
  */
 public class CsvWriterExtend extends CsvWriter {
     private PrintWriter outputStream;
     private String fileName;
     private boolean firstColumn;
     private boolean useCustomRecordDelimiter;
     private Charset charset;
     private CsvWriterExtend.UserSettings userSettings;
     private boolean initialized;
     private boolean closed;
     public static final int ESCAPE_MODE_DOUBLED = 1;
     public static final int ESCAPE_MODE_BACKSLASH = 2;
     private String sheetFirstName;

     public CsvWriterExtend(String var1, char var2, Charset var3,String sheetFirstName) {
         super(var1,var2,var3);
         this.outputStream = null;
         this.fileName = null;
         this.firstColumn = true;
         this.useCustomRecordDelimiter = false;
         this.charset = null;
         this.userSettings = new CsvWriterExtend.UserSettings();
         this.initialized = false;
         this.closed = false;
         //1：这里加了一个csv表头的第一个名字字段，用来解决第一个问题：中文乱码问题
         this.sheetFirstName = sheetFirstName;
         if (var1 == null) {
             throw new IllegalArgumentException("Parameter fileName can not be null.");
         } else if (var3 == null) {
             throw new IllegalArgumentException("Parameter charset can not be null.");
         } else {
             this.fileName = var1;
             this.userSettings.Delimiter = var2;
             this.charset = var3;
         }
     }

     public CsvWriterExtend(Writer var1, char var2) {
         super(var1,var2);
         this.outputStream = null;
         this.fileName = null;
         this.firstColumn = true;
         this.useCustomRecordDelimiter = false;
         this.charset = null;
         this.userSettings = new CsvWriterExtend.UserSettings();
         this.initialized = false;
         this.closed = false;
         if (var1 == null) {
             throw new IllegalArgumentException("Parameter outputStream can not be null.");
         } else {
             this.outputStream = new PrintWriter(var1);
             this.userSettings.Delimiter = var2;
             this.initialized = true;
         }
     }

     public CsvWriterExtend(OutputStream var1, char var2, Charset var3) {
         this(new OutputStreamWriter(var1, var3), var2);
     }

     public char getDelimiter() {
         return this.userSettings.Delimiter;
     }

     public void setDelimiter(char var1) {
         this.userSettings.Delimiter = var1;
     }

     public char getRecordDelimiter() {
         return this.userSettings.RecordDelimiter;
     }

     public void setRecordDelimiter(char var1) {
         this.useCustomRecordDelimiter = true;
         this.userSettings.RecordDelimiter = var1;
     }

     public char getTextQualifier() {
         return this.userSettings.TextQualifier;
     }

     public void setTextQualifier(char var1) {
         this.userSettings.TextQualifier = var1;
     }

     public boolean getUseTextQualifier() {
         return this.userSettings.UseTextQualifier;
     }

     public void setUseTextQualifier(boolean var1) {
         this.userSettings.UseTextQualifier = var1;
     }

     public int getEscapeMode() {
         return this.userSettings.EscapeMode;
     }

     public void setEscapeMode(int var1) {
         this.userSettings.EscapeMode = var1;
     }

     public void setComment(char var1) {
         this.userSettings.Comment = var1;
     }

     public char getComment() {
         return this.userSettings.Comment;
     }

     public boolean getForceQualifier() {
         return this.userSettings.ForceQualifier;
     }

     public void setForceQualifier(boolean var1) {
         this.userSettings.ForceQualifier = var1;
     }

     public void write(String var1, boolean var2) throws IOException {
         this.checkClosed();
         this.checkInit();
         if (var1 == null) {
             var1 = "";
         }
         //2：这里加了一个判断条件，用来解决第一个问题：中文乱码问题
         //加的目的是：如果是写入bom则bom后面不追加逗号，即在bom后面和第一个表头前面，即两者之间不追加逗号,sheetFirstName为第一个表头的名字根据实际传入
         if (!this.firstColumn && !var1.contentEquals(sheetFirstName) ){
             this.outputStream.write(this.userSettings.Delimiter);
         }

         boolean var3 = this.userSettings.ForceQualifier;
         if (!var2 && var1.length() > 0) {
             var1 = var1.trim();
         }

         if (!var3 && this.userSettings.UseTextQualifier && (var1.indexOf(this.userSettings.TextQualifier) > -1 || var1.indexOf(this.userSettings.Delimiter) > -1 || !this.useCustomRecordDelimiter && (var1.indexOf(10) > -1 || var1.indexOf(13) > -1) || this.useCustomRecordDelimiter && var1.indexOf(this.userSettings.RecordDelimiter) > -1 || this.firstColumn && var1.length() > 0 && var1.charAt(0) == this.userSettings.Comment || this.firstColumn && var1.length() == 0)) {
             var3 = true;
         }

         if (this.userSettings.UseTextQualifier && !var3 && var1.length() > 0 && var2) {
             char var4 = var1.charAt(0);
             if (var4 == ' ' || var4 == '\t') {
                 var3 = true;
             }

             if (!var3 && var1.length() > 1) {
                 char var5 = var1.charAt(var1.length() - 1);
                 if (var5 == ' ' || var5 == '\t') {
                     var3 = true;
                 }
             }
         }
         //3：这里加了一个if语句，是为了解决第三个问题：csv""显示null的问题
         if(!this.firstColumn && var1.length()==0){
             var3=true;
         }
         if (var3) {
             this.outputStream.write(this.userSettings.TextQualifier);
             if (this.userSettings.EscapeMode == 2) {
                 var1 = replace(var1, "\\", "\\\\");
                 var1 = replace(var1, "" + this.userSettings.TextQualifier, "\\" + this.userSettings.TextQualifier);
             } else {
                 var1 = replace(var1, "" + this.userSettings.TextQualifier, "" + this.userSettings.TextQualifier + this.userSettings.TextQualifier);
             }
         } else if (this.userSettings.EscapeMode == 2) {
             var1 = replace(var1, "\\", "\\\\");
             var1 = replace(var1, "" + this.userSettings.Delimiter, "\\" + this.userSettings.Delimiter);
             if (this.useCustomRecordDelimiter) {
                 var1 = replace(var1, "" + this.userSettings.RecordDelimiter, "\\" + this.userSettings.RecordDelimiter);
             } else {
                 var1 = replace(var1, "\r", "\\\r");
                 var1 = replace(var1, "\n", "\\\n");
             }

             if (this.firstColumn && var1.length() > 0 && var1.charAt(0) == this.userSettings.Comment) {
                 if (var1.length() > 1) {
                     var1 = "\\" + this.userSettings.Comment + var1.substring(1);
                 } else {
                     var1 = "\\" + this.userSettings.Comment;
                 }
             }
         }

         this.outputStream.write(var1);

         if (var3) {
             this.outputStream.write(this.userSettings.TextQualifier);
         }

         this.firstColumn = false;
     }

     public void write(String var1) throws IOException {
         this.write(var1, false);
     }

     public void writeComment(String var1) throws IOException {
         this.checkClosed();
         this.checkInit();
         this.outputStream.write(this.userSettings.Comment);
         this.outputStream.write(var1);
         if (this.useCustomRecordDelimiter) {
             this.outputStream.write(this.userSettings.RecordDelimiter);
         } else {
             this.outputStream.println();
         }

         this.firstColumn = true;
     }

     public void writeRecord(String[] var1, boolean var2) throws IOException {
         if (var1 != null && var1.length > 0) {
             for(int var3 = 0; var3 < var1.length; ++var3) {
                 this.write(var1[var3], var2);
             }

             this.endRecord();
         }

     }

     public void writeRecord(String[] var1) throws IOException {
         this.writeRecord(var1, false);
     }

     public void writeLastRecord(String[] var1) throws IOException {
         this.writeLastRecord(var1, false);
     }

     //4：这里加了两个方法writeLastRecord和endLastRecord，用来解决第二个问题：某尾总是多一行空行的问题
     public void writeLastRecord(String[] var1, boolean var2) throws IOException {
         if (var1 != null && var1.length > 0) {
             for(int var3 = 0; var3 < var1.length; ++var3) {
                 this.write(var1[var3], var2);
             }

             this.endLastRecord();
         }

     }
     public void endLastRecord() throws IOException {
         this.checkClosed();
         this.checkInit();
         if (this.useCustomRecordDelimiter) {
             this.outputStream.write(this.userSettings.RecordDelimiter);
         } else {//主要在下面这一行，当执行这个方法来结尾的时候是不追加换行符的
             this.outputStream.print("");
         }

         this.firstColumn = true;
     }

     public void endRecord() throws IOException {
         this.checkClosed();
         this.checkInit();
         if (this.useCustomRecordDelimiter) {
             this.outputStream.write(this.userSettings.RecordDelimiter);
         } else {
             this.outputStream.println();
         }

         this.firstColumn = true;
     }

     private void checkInit() throws IOException {
         if (!this.initialized) {
             if (this.fileName != null) {
                 this.outputStream = new PrintWriter(new OutputStreamWriter(new FileOutputStream(this.fileName), this.charset));
             }

             this.initialized = true;
         }

     }

     public void flush() {
         this.outputStream.flush();
     }

     public void close() {
         if (!this.closed) {
             this.close(true);
             this.closed = true;
         }

     }

     private void close(boolean var1) {
         if (!this.closed) {
             if (var1) {
                 this.charset = null;
             }

             try {
                 if (this.initialized) {
                     this.outputStream.close();
                 }
             } catch (Exception var3) {
                 ;
             }

             this.outputStream = null;
             this.closed = true;
         }

     }

     private void checkClosed() throws IOException {
         if (this.closed) {
             throw new IOException("This instance of the CsvWriter class has already been closed.");
         }
     }

     protected void finalize() {
         this.close(false);
     }

     public static String replace(String var0, String var1, String var2) {
         int var3 = var1.length();
         int var4 = var0.indexOf(var1);
         if (var4 <= -1) {
             return var0;
         } else {
             StringBuffer var5 = new StringBuffer();

             int var6;
             for(var6 = 0; var4 != -1; var4 = var0.indexOf(var1, var6)) {
                 var5.append(var0.substring(var6, var4));
                 var5.append(var2);
                 var6 = var4 + var3;
             }

             var5.append(var0.substring(var6));
             return var5.toString();
         }
     }

     private class UserSettings {
         public char TextQualifier = '"';
         public boolean UseTextQualifier = true;
         public char Delimiter = ',';
         public char RecordDelimiter = 0;
         public char Comment = '#';
         public int EscapeMode = 1;
         public boolean ForceQualifier = false;

         public UserSettings() {
         }
     }

     private class Letters {
         public static final char LF = '\n';
         public static final char CR = '\r';
         public static final char QUOTE = '"';
         public static final char COMMA = ',';
         public static final char SPACE = ' ';
         public static final char TAB = '\t';
         public static final char POUND = '#';
         public static final char BACKSLASH = '\\';
         public static final char NULL = '\u0000';

         private Letters() {
         }
     }
 }            

四：调用写好的CsvWriterExtend类，实现写csv功能

下面给出写csv的方法，如下红色部分是解决上诉三个问题的关键：中文乱码、末尾行多一行空格(/r)、非第一列空字符串""显示null问题

  /**
      * 写csv方法
      */
     public static <T> void writeCSV(Collection<T> dataset, String csvFilePath, String[] csvHeaders) {

         try {
             //集合长度，和循环次数，当循环到最后一条记录时不在末尾插入换行符
             int datasetLength = dataset.size();
             int loop=1;
             // 定义路径，分隔符，编码d，第一个表头名称
             //如果是写入bom则bom后面不追加逗号，即在bom后面和第一个表头前面，即两者之间不追加逗号,sheetFirstName为第一个表头的名字根据实际传入
             CsvWriterExtend csvWriter = new CsvWriterExtend(csvFilePath, ',', Charset.forName("UTF-8"),"username"); // 写表头
             //如果是写入bom解决文件乱码，则不在bom后面追加,号分隔符
             csvWriter.write("\ufeff");
             csvWriter.writeRecord(csvHeaders); // 写内容
             // 遍历集合
             Iterator<T> it = dataset.iterator();
             while (it.hasNext()) {
                 T t = (T) it.next();
                 //获取类属性
                 Field[] fields = t.getClass().getDeclaredFields();
                 String[] csvContent=new String[fields.length];
                 for (short i = 0; i < fields.length; i++) {
                     Field field = fields[i];
                     String fieldName = field.getName();
                     String getMethodName = "get" + fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);
                     try {
                         Class tCls = t.getClass();
                         Method getMethod = tCls.getMethod(getMethodName,new Class[] {});
                         Object value = getMethod.invoke(t, new Object[] {});
                         if (value == null) {
                             continue;
                         }
                         //取值并赋给数组
                         String textvalue=value.toString();
                         csvContent[i]=textvalue;
                     }catch (Exception e) {
                         e.getStackTrace();
                     }
                 }
                 if(loop!=datasetLength){
                     //迭代插入记录
                     csvWriter.writeRecord(csvContent);
                 }else{
                     //插入最后一条记录
                     csvWriter.writeLastRecord(csvContent);
                 }

                 loop=loop+1;
                 for(String csvs:csvContent) {
                     System.out.println("记录数据：" + csvs);
                 }
             } csvWriter.close();
             System.out.println("<--------CSV文件写入成功-------->");
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

调用csv方法即执行类

 public static void main(String[] args) throws Exception{
         //造测试数据
         List<DataEntity> data = CreateDataModel.createUserData();
         String csvFilePath = "E://data.csv";
         //表头名称
         //注册用户名、注册密码、登录用户名、登录密码、记住我、邮箱、分类名称、文章标题、文章路径、文章标签、文章内容、评论文章、期望结果
         String[] csvHeaders = { "username", "password", "loginusername","loginpassword","remeber","email","cname","title","slug","tags","content","comment","expectresult" };
         CreateDataModel.writeCSV(data,csvFilePath,csvHeaders);

     }

生成csv的效果如图：

四：备注

如果想看更详细的代码，可参考我的github地址，如上csv的生成已全部上传github中，地址如下：

https://github.com/mmkxyu/auto-create-test-data.git

博文均为原创文章，转载请注明出处，感谢！