Question

这是我的班级，

public class FreebasePeopleResults {

public String intendedSearch;
public String weight;
public Double heightMeters;
public Integer age;
public String type;
public String parents;
public String profession;
public String alias;
public String children;
public String siblings;
public String spouse;
public String degree;
public String institution;
public String wikipediaId;
public String guid;
public String id;
public String gender;
public String name;
public String ethnicity;
public String articleText;
public String dob;

public String getWeight() {
    return weight;
}
public void setWeight(String weight) {
    this.weight = weight;
}
public Double getHeightMeters() {
    return heightMeters;
}
public void setHeightMeters(Double heightMeters) {
    this.heightMeters = heightMeters;
}
public String getParents() {
    return parents;
}
public void setParents(String parents) {
    this.parents = parents;
}
public Integer getAge() {
    return age;
}
public void setAge(Integer age) {
    this.age = age;
}       
public String getProfession() {
    return profession;
}
public void setProfession(String profession) {
    this.profession = profession;
}
public String getAlias() {
    return alias;
}
public void setAlias(String alias) {
    this.alias = alias;
}
public String getChildren() {
    return children;
}
public void setChildren(String children) {
    this.children = children;
}
public String getSpouse() {
    return spouse;
}
public void setSpouse(String spouse) {
    this.spouse = spouse;
}
public String getDegree() {
    return degree;
}
public void setDegree(String degree) {
    this.degree = degree;
}
public String getInstitution() {
    return institution;
}
public void setInstitution(String institution) {
    this.institution = institution;
}
public String getWikipediaId() {
    return wikipediaId;
}
public void setWikipediaId(String wikipediaId) {
    this.wikipediaId = wikipediaId;
}
public String getGuid() {
    return guid;
}
public void setGuid(String guid) {
    this.guid = guid;
}
public String getId() {
    return id;
}
public void setId(String id) {
    this.id = id;
}
public String getGender() {
    return gender;
}
public void setGender(String gender) {
    this.gender = gender;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public String getEthnicity() {
    return ethnicity;
}
public void setEthnicity(String ethnicity) {
    this.ethnicity = ethnicity;
}
public String getArticleText() {
    return articleText;
}
public void setArticleText(String articleText) {
    this.articleText = articleText;
}
public String getDob() {
    return dob;
}
public void setDob(String dob) {
    this.dob = dob;
}
public String getType() {
    return type;
}
public void setType(String type) {
    this.type = type;
}
public String getSiblings() {
    return siblings;
}
public void setSiblings(String siblings) {
    this.siblings = siblings;
}
public String getIntendedSearch() {
    return intendedSearch;
}
public void setIntendedSearch(String intendedSearch) {
    this.intendedSearch = intendedSearch;
}

}

这是我的CSV编写器方法

 import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;

import org.supercsv.io.CsvBeanWriter;
import org.supercsv.prefs.CsvPreference;

public class CSVUtils {

    public static void writeCSVFromList(ArrayList<FreebasePeopleResults> people, boolean writeHeader) throws IOException{

        //String[] header = new String []{"title","acronym","globalId","interfaceId","developer","description","publisher","genre","subGenre","platform","esrb","reviewScore","releaseDate","price","cheatArticleId"};
        FileWriter file = new FileWriter("/brian/brian/Documents/people-freebase.csv", true);

        // write the partial data
        CsvBeanWriter writer = new CsvBeanWriter(file, CsvPreference.EXCEL_PREFERENCE);

        for(FreebasePeopleResults person:people){
            writer.write(person);
        }
        writer.close();
        // show output
    }           
}

我一直收到输出错误。这是错误：第2行上下文没有要写的内容：行：2列：0原始行：空

现在，我知道它现在完全无效，所以我很困惑。

Answer 1

所以已经有一段时间了，你可能已经离开了这个，但是......

问题实际上是你没有向write()方法提供标题，即它应该是

writer.write(person, header);

不幸的是，API在write()方法的签名中使用var-args表示法有点误导，因为它允许null传入.javadoc明确指出你不应该这样做，但是在实现中没有空检查：因此你得到了例外。

/**
 * Write an object
 * 
 * @param source
 *            at object (bean instance) whose values to extract
 * @param nameMapping
 *            defines the fields of the class that must be written. 
 *            null values are not allowed
 * @since 1.0
 */
public void write(Object source, String... nameMapping) throws IOException,
    SuperCSVReflectionException;

Super CSV 2.0.0-beta-1现在已经出局了。它保留了write()方法中的var-args，但是如果你提供null就会快速失败，所以当你得到一个NullPointerException以及以下内容时你确切地知道错误：

nameMapping数组不能为null，因为它用于从字段映射到列

它还包含许多错误修复和新功能（包括Maven支持和用于映射嵌套属性和数组/集合的新Dozer扩展）。

Answer 2

我看不到您创建ArrayList<FreebasePeopleResults> people的位置，但您可能会验证它有多个元素。作为coding to the interface的示例，请考虑使用List<FreebasePeopleResults> people作为形式参数。

附录：您是否能够使Code example: Write a file with a header工作？

示例：这是一个简化的示例。我想你只需要在调用nameMapping时指定write()。这些名称决定了通过内省调用方法的内容。

控制台输出：

name,age
Alpha,1
Beta,2
Gamma,3

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import org.supercsv.io.CsvBeanWriter;
import org.supercsv.io.ICsvBeanWriter;
import org.supercsv.prefs.CsvPreference;

public class Main {

    private static final List<Person> people = new ArrayList<Person>();

    public static void main(String[] args) throws IOException {
        people.add(new Person("Alpha", 1));
        people.add(new Person("Beta", 2));
        people.add(new Person("Gamma", 3));
        ICsvBeanWriter writer = new CsvBeanWriter(
            new PrintWriter(System.out), CsvPreference.STANDARD_PREFERENCE);
        try {
            final String[] nameMapping = new String[]{"name", "age"};
            writer.writeHeader(nameMapping);
            for (Person p : people) {
                writer.write(p, nameMapping);
            }
        } finally {
            writer.close();
        }
    }
}

public class Person {

    String name;
    Integer age;

    public Person(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Answer 3

CellProcessor[] processors = new CellProcessor[] { new Optional(), new NotNull(),
                new Optional(), new Optional(), new NotNull(), new Optional()};

CsvBeanWriter writer = new CsvBeanWriter(file, CsvPreference.EXCEL_PREFERENCE)

writer.write(data,properties,processors);

SUPER CSV将bean写入CSV

3 个答案: