List 转markdown表格字符串

之前有碰到一个需求，要求将数据库查询的数据输出为markdown文件。遇到的主要问题是List<T>转markdown表格。主要思路如下：

• 创建注解，用于标记对象字段对应的表头名称和顺序
• 根据注解生成表头
• 根据注解将T的对应值按顺序生成字符串
• 将表头和内容字符串拼接

创建注解

    /** 定义注解*/
    @Target(ElementType.FIELD)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface FiledInfo{
        // 指定对应的表头名称
        String alias() default "";
        // 指定顺序
        int order() default -1;
    }

主要代码

private static final String SEP_ROW = " ----- |";
private static final String SEP = "|";
private static final String BLANK = "";


/** list内容转为markdown表格*/
public static <T> String convertTable(List<T> list, Class<T> clazz){
    Field[] fields =  clazz.getFields();
    if(fields.length == 0){
        fields = clazz.getDeclaredFields();
    }
    // 对字段排序
    List<Field> fieldList = new ArrayList<>(Arrays.asList(fields));
    fieldList.removeIf( e-> getAnnotation(e) == null);
    fieldList.sort(Comparator.comparingInt(e -> getAnnotation(e).order()));

    StringBuilder markdown = new StringBuilder();
    // 生成表头
    markdown.append(initTableHead(fieldList));
    // 生成分隔行
    markdown.append(initSepRow(fieldList.size()));
    // 添加表格内容
    list.forEach(e->{
        StringBuilder row = new StringBuilder(SEP);
        fieldList.forEach(field ->{
            try {
                Object object = fieldGetMethod(field,clazz).invoke(e);
                row.append(object == null ? BLANK : object).append(SEP);
            } catch (IllegalAccessException | InvocationTargetException | NoSuchMethodException ex) {
                throw new RuntimeException(ex);
            }
        });
        row.append("\n");
        markdown.append(row);
    });
    return markdown.toString();
}

/** 初始化表头*/
private static String initTableHead(List<Field> fieldList) {
    StringBuilder builder = new StringBuilder(SEP);
    fieldList.forEach(e-> builder.append(getAnnotation(e).alias()).append(SEP));
    builder.append("\n");
    return builder.toString();
}

/** 生成分隔行*/
private static String initSepRow(int size) {
    StringBuilder builder = new StringBuilder(SEP);
    for(int i = 0;i<size;i++){
        builder.append(SEP_ROW);
    }
    builder.append("\n");
    return builder.toString();
}

测试

@Data
public class CustomBean{
    @MarkdownUtil.FiledInfo(alias = "姓名",order = 0)
    private String name;
    @MarkdownUtil.FiledInfo(alias = "性别",order = 3)
    private String gender;
    @MarkdownUtil.FiledInfo(alias = "年龄",order = 2)
    private String age;
    @MarkdownUtil.FiledInfo(alias = "国籍",order = 5)
    private String nation;
    @MarkdownUtil.FiledInfo(alias = "职业",order = 4)
    private String job;

    public CustomBean(String name, String gender, String age, String nation, String job){
        this.name = name;
        this.gender = gender;
        this.age = age;
        this.nation = nation;
        this.job = job;
    }
}



public static void main(String[] args) {
    List<CustomBean> list =new ArrayList<>();
    list.add(new CustomBean("LiLei","male","25","China","worker"));
    System.out.println(convertTable(list, CustomBean.class));
}