在Jackson ObjectMapper上配置缩进间距的最简单方法是什么？

问题描述

我真的在努力解决我在解决这个问题时所感受到的复杂程度。正如标题所说：使用4空格 PrettyPrinter 创建Jackson ObjectMapper 的简单方法是什么？ ？

I'm really struggling with the degree of complexity I am perceiving in solving this problem. As the title says: What is a simple way to create a Jackson ObjectMapper with a 4-space PrettyPrinter?

奖励积分：如何修改现有 ObjectMapper 使它漂亮打印4个空格？

Bonus points: How can I modify an existing ObjectMapper to make it pretty print 4 spaces?

通过我的研究，我发现最简单的方法是启用漂亮的打印通常是设置映射器上的INDENT_OUTPUT ：

Through my research, I've found that the simplest way is to enable pretty printing generally is to set INDENT_OUTPUT on the mapper:

objectMapper.enable(SerializationFeature.INDENT_OUTPUT);

但是，这只能启用 DefaultPrettyPrinter ，有2个压痕空间。我想4.要做到这一点，似乎我必须构建自己的 ObjectMapper ，提供 JsonFactory 一个 JsonGenerator ，它有一个 PrettyPrinter ，它有4个空格。对于在其他平台上如此简单的东西来说，这太过激烈了。请告诉我有一种更简单的方法。

However, this only enables the the DefaultPrettyPrinter, which has 2 spaces of indentation. I would like 4. To do this, it seems like I have to construct my own ObjectMapper, providing a JsonFactory with a JsonGenerator that has a PrettyPrinter that does 4 spaces. This is way too intense for something that is so so so simple on other platforms. Please tell me there is a simpler way.

推荐答案

我不确定这是否是最简单的但是......你可以使用自定义打印机使用 ObjectMapper 。如果您修改缩进行为，则可以使用 DefaultPrettyPrinter 。

I am not sure if this is the simplest way to go but... You can use the ObjectMapper with a custom printer. The DefaultPrettyPrinter can be used if you modify the indent behaviour.

// Create the mapper
ObjectMapper mapper = new ObjectMapper();

// Setup a pretty printer with an indenter (indenter has 4 spaces in this case)
DefaultPrettyPrinter.Indenter indenter =
        new DefaultIndenter("    ", DefaultIndenter.SYS_LF);
DefaultPrettyPrinter printer = new DefaultPrettyPrinter();
printer.indentObjectsWith(indenter);
printer.indentArraysWith(indenter);

// Some object to serialize
Map<String, Object> value = new HashMap<>();
value.put("foo", Arrays.asList("a", "b", "c"));

// Serialize it using the custom printer
String json = mapper.writer(printer).writeValueAsString(value);

// Print it
System.out.println(json);

输出将是：

{
    "foo" : [
        "a",
        "b",
        "c"
    ]
}

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