如何在 Salesforce Apex 中解析 YAML 对象

Question

我从 Apex 代码中的 REST 服务响应中得到一个 YAML 字符串，我寻找一些类似的方法来解析它并将其转换为 Salesforce 对象的集合。

例如，我得到这样的 YAML 作为字符串：

---
item:
  - 
    title: A Grief Observed
    author: C. S. Lewis
    author_by_last: Lewis, C. S.
    isbn: "0060652381"
    publisher: ZOND
    on_hand: "5"
    in_pub_date: 2001-01-01
  - 
    title: "Grief Sanctified: From Sorrow to Eternal Hope: Including Richard Baxter's Timeles"
    author: J. I. Packer
    author_by_last: Packer, J. I.
    isbn: "1581344406"
    publisher: CROSS
    on_hand: "5"
    in_pub_date: 2002-09-01

我想将其转换为 Book 对象列表。当我使用 JSON 时，我使用了 JSON class，它提供了反序列化功能，我想知道，Salesforce 是否为 YAML 处理提供了类似的东西？

Answer 1

注意：这是 copy/pasted 我在 same question on the Salesforce SE site 上给出的答案。

不，在撰写本文时 (API v41.0)，Salesforce 没有任何内置功能来创建或解析 YAML。这意味着您需要构建自己的（或将现有语言从另一种语言改编成 Apex，例如 Java）。

如果您不是在寻找通用解析器（可以处理任何有效 YAML 的东西）并且您不希望您接收的数据格式发生变化，请编写一个特定于域的解析器不应该做太多工作。

当我发现自己在使用 XML 时，我喜欢将传入的模式分解为单独的顶点类并在每个顶点中构建解析方法。这样做可以使解析器易于管理。 YAML 也可以采用类似的方法。

// Yes, the need for this BookCollection object is debatable (it's mainly just storing
//   a List).
// Encapsulating the parsing makes it worth being made into a class (in my mind).
public class BookCollection{
    // The class variables for each level mimic the data stored on each level
    //   of the schema of your incoming data.
    // This will become more apparent later.
    public List<Book> item;

    public BookCollection(String input){
        item = new List<Book>();

        // At this level, all we're concerned about is finding the individual books.
        // Once we find a book, we pass it down to the next level of parsing (and
        //   add the result to our list)
        // YAML uses whitespace to denote structure, so we need to take that into
        //   account when splitting.
        // The regex here looks for two spaces, a hyphen, one space, a newline.
        // Everything after that (up to the next '  - \n' or EOF) is book data.

        // String.split() will return 'item:' as the first part.
        // That isn't part of the data for a book, so we'll want to remove that.
        List<String> bookStringsList = input.split('  - \n');
        bookStringsList.remove(0);

        for(String bookString :bookStringsList){
            Book currentBook = new Book(bookString);
            item.add(currentBook);
        }
    }
}

public class Book{
    // Now it should be more apparent that we're mimicking the structure of the
    //   incoming data.
    String title;
    String author;
    String author_by_last;
    String isbn;
    String publisher;
    Integer on_hand;
    Date in_pub_date;

    public Book(String input){
        // On this level of parsing, we have actual data to work with.
        // Our job here is to find all of the key:value pairs, and cast them to
        //   their appropriate types.
        for(String keyAndValue :input.split('    \n')){
            String key, value;
            List<String> kvSplit = keyAndValue.split(':');
            key = kvSplit[0];
            // Double quotes are likely to mess things up, so remove them.
            value = kvSplit[1].replace('"', '');

            // There's probably a more elegant way to handle this than a big 'ol
            //   if/else if chain...but this'll work
            if(key == 'title'){
                this.title = value;
            } else if(key == 'author'){
                this.author = value;
            } else if(key == 'author_by_last'){
                this.author_by_last = value;
            } else if(key == 'isbn'){
                this.isbn = value;
            } else if(key == 'publisher'){
                this.publisher = value;
            } else if(key == 'on_hand'){
                // String -> Integer is pretty easy, we can use Integer.valueOf()
                this.on_hand = Integer.valueOf(value);
            } else if(key == 'in_pub_date'){
                // Dates are a bit tricky.
                // Salesforce wants them in YYYY-MM-DDThh:mm:ssZ format, or the format
                //   used in your locale (for parse() or valueOf()).
                // Given our data, it's easiest to simply generate a new date instance
                List<String> dateParts = value.split('-');

                this.in_pub_date = Date.newInstance(dateParts[0], dateParts[1], dateParts[2]);
            }
        }
    }
}

使用这些类非常简单。但是，它确实需要一些额外的设置。

// Your YAML, from some source
String myYAML = blackBox.getData();

// Break up your YAML's documents before attempting to parse each one.
List<String> documents = myYAML.split('---\n');

// The first result string will likely always be empty, so we can remove that.
documents.remove(0);

// This is the simple case where we know we're only dealing with a single document.
// If you had multiple documents in a single YAML string, you would (hopefully)
//   be able to tell which type of document you were working with (and you'd
//   need additional logic to determine which parser class to send the data to).
BookCollection myBooks = new BookCollection(documents[0]);

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