Java实现对象转CSV格式
介绍
csv全称“Comma-Separated Values”，是一种逗号分隔值格式的文件，是一种用来存储数据的纯文本格式文件。CSV文件由任意数目的记录组成，记录间以某种换行符分隔；每条记录由字段组成，字段间的分隔符是其它字符或字符串。
Java对象转CSV,有现成的工具包,commons-lang3 的ReflectionToStringBuilder 就可以简单的解决的对象转CSV 但是复杂点的处理还是不行,而且在运行速度上,我测试了下我自己写的,比这个快多了,1百万条数据大约也就2秒左右, 如果对速度有要求的话,我们可以使用多线程进行分割,比如1千万条数据,那么我开10个线程,1个线程执行100万条数据,所有线程执行完毕后在按照顺序拼接到一起,这样1千万条数据也就最多3~5秒执行完毕
代码样例
package com.file.csv;
import com.date.LocalDateUtils;
import lombok.Data;
import lombok.SneakyThrows;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Function;
@Data
public class ObjToCSV<T> {
private String separator = "\u0001|\u0001"; //默认分隔符
private StringBuilder str = new StringBuilder();
private T object;
private List<T> objects;
private List<String> excludeFields = new ArrayList<String>(100) {{
add("serialVersionUID");
}};
private List<String> includeFields = new ArrayList<String>(100);
private boolean fieldsAll = false;
private int number;//多少行一共
//日期串 20220617204504
private String createDate=LocalDateUtils.getLocalDateTimeStr1() ;
private ObjToCSV(T object, String separator) {
this.object = object;
this.separator = separator;
//行数
this.number=1;
}
private ObjToCSV(T object) {
this.object = object;
//行数
this.number=1;
}
private ObjToCSV(List<T> objects) {
if (objects.isEmpty()) {
throw new NullPointerException("不能是空");
}
this.object = objects.get(0);
this.objects = objects;
//行数
this.number=objects.size();
}
private ObjToCSV(List<T> objects, String separator) {
if (objects.isEmpty()) {
throw new NullPointerException("不能是空");
}
this.object = objects.get(0);
this.objects = objects;
this.separator = separator;
//行数
this.number=objects.size();
}
// 排除和包含都有,那么以包含的为主
private boolean decideFields(String fieldName) {
//包含
if (includeFields.contains(fieldName)) {
return false;
}
//排除
if (excludeFields.contains(fieldName)) {
return true;
}
// 开启全部放行
if (fieldsAll) {
return false;
}
//默认拦截全部
return true;
}
public static <T> ObjToCSV<T> create(T object, String separator) {
return new ObjToCSV<T>(object, separator);
}
public static <T> ObjToCSV<T> create(T object) {
return new ObjToCSV<T>(object);
}
public static <T> ObjToCSV<T> create(List<T> object, String separator) {
return new ObjToCSV<T>(object, separator);
}
public static <T> ObjToCSV<T> create(List<T> object) {
return new ObjToCSV<T>(object);
}
//全部放行
public ObjToCSV<T> fieldsAll() {
fieldsAll = true;
return this;
}
//包含
public ObjToCSV<T> addIncludeFields(String... fieldName) {
includeFields.addAll(Arrays.asList(fieldName));
return this;
}
//排除
public ObjToCSV<T> addExcludeFields(String... fieldName) {
excludeFields.addAll(Arrays.asList(fieldName));
return this;
}
//添加头部
public ObjToCSV<T> addHead() {
StringBuilder str1 = new StringBuilder();
Class<?> aClass = this.object.getClass();
Field[] fields = aClass.getDeclaredFields();
int length = fields.length;
for (int i = 0; i < length; i++) {
Field field = fields[i];
field.setAccessible(true);
if (decideFields(field.getName())) {
continue;
}
str1.append(field.getName()).append(separator);
}
int length1 = separator.length();
String substring = str1.substring(0, str1.length() - length1);
this.str.append(substring + "\n");
return this;
}
//在结尾补充自定义的描述
public ObjToCSV<T> addEnding(Function<ObjToCSV,String> functor){
String apply = functor.apply( this);
this.str.append(apply);
return this;
}
//将对象转换为CSV格式字符串
@SneakyThrows
public ObjToCSV<T> addContent() {
StringBuilder str1 = new StringBuilder();
Class<?> aClass = this.object.getClass();
Field[] fields = aClass.getDeclaredFields();
int length = fields.length;
for (int i = 0; i < length; i++) {
Field field = fields[i];
field.setAccessible(true);
if (decideFields(field.getName())) {
continue;
}
Object o = field.get(object);
String value = "";
if (o != null) {
value = String.valueOf(o);
}
str1.append(value).append(separator);
}
int length1 = separator.length();
String substring = str1.substring(0, str1.length() - length1);
this.str.append(substring + "\n");
return this;
}
//将多个对象转换为csv格式
public ObjToCSV<T> addContents() {
for (T t : this.objects) {
this.object=t;
addContent();
}
return this;
}
//将结果输出为字符串
public String ToString() {
return str.toString();
}
}测试样例
package com.file;
import com.alibaba.fastJSON.jsONObject;
import com.data.RandomUserData;
import com.entity.UserData;
import com.file.csv.ObjToCSV;
import com.file.csv.ObjToCSV;
import com.function.impl.CodeStartAndStopTimeUtil;
import lombok.SneakyThrows;
import org.junit.Test;
import java.util.List;
public class ObjToCSVTest {
//单个对象
@Test
public void show1(){
UserData userOne = RandomUserData.getUserOne();
String s = ObjToCSV.create(userOne)
.fieldsAll()
// .addIncludeFields()
.addExcludeFields("roleData")
// .addHead()
.addContent()
// .addContents()
.addEnding((data)->{
JSONObject jsonObject = new JSONObject();
jsonObject.put("count",data.getNumber());
jsonObject.put("time",data.getCreateDate());
jsonObject.put("separator",data.getSeparator());
return jsonObject.toJSONString();
})
.ToString();
System.out.println(s);
}
//多个对象,可以使用自定义分隔符
@Test
public void show2(){
UserData userOne = RandomUserData.getUserOne();
String s = ObjToCSV.create(userOne,"|")
.fieldsAll()
.addExcludeFields("roleData")
.addContent()
.addEnding((data)->{
JSONObject jsonObject = new JSONObject();
jsonObject.put("count",data.getNumber());
jsonObject.put("time",data.getCreateDate());
jsonObject.put("separator",data.getSeparator());
return jsonObject.toJSONString();
})
.ToString();
System.out.println(s);
}
//排除不显示的,其他都显示
@Test
public void show3(){
List<UserData> userDatas = RandomUserData.getUserDatas(10);
String s = ObjToCSV.create(userDatas,"|")
.fieldsAll()//显示全部字段
.addExcludeFields("roleData")//排除指定字段
.addHead()
.addContents()
.addEnding((data)->{
JSONObject jsonObject = new JSONObject();
jsonObject.put("count",data.getNumber());
jsonObject.put("time",data.getCreateDate());
jsonObject.put("separator",data.getSeparator());
return jsonObject.toJSONString();
})
.ToString();
System.out.println(s);
}
//只包含指定字段 ,其他都不显示
@Test
public void show4(){
List<UserData> userDatas = RandomUserData.getUserDatas(10);
String s = ObjToCSV.create(userDatas,"|")
.addIncludeFields("id","name")
.addHead() //添加头部
.addContents() //添加内容
.addEnding((data)->{ //添加结尾信息
JSONObject jsonObject = new JSONObject();
jsonObject.put("count",data.getNumber());
jsonObject.put("time",data.getCreateDate());
jsonObject.put("separator",data.getSeparator());
return jsonObject.toJSONString();
})
.ToString();
System.out.println(s);
}
//内容
@Test
public void show5(){
List<UserData> userDatas = RandomUserData.getUserDatas(10);
String s = ObjToCSV.create(userDatas,"|")
.fieldsAll()
.addExcludeFields("roleData")//排除指定字段
.addContents() //添加内容
.ToString();
System.out.println(s);
}
@SneakyThrows
public static void main(String[] args) {
List<UserData> userDatas = RandomUserData.getUserDatas(100);
String s = ObjToCSV.create(userDatas)
.fieldsAll()
// .addIncludeFields()
.addExcludeFields("roleData")
// .addHead()
// .addContent()
.addContents()
.addEnding((data)->{
JSONObject jsonObject = new JSONObject();
jsonObject.put("count",data.getNumber());
jsonObject.put("time",data.getCreateDate());
return jsonObject.toJSONString();
})
.ToString();
System.out.println(s);
}
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