杰克逊JSON反序列化：在每一行数组元素

Question

我使用Jackson并想漂亮地打印JSON，使得在阵列中的每个元素进行到每一行，如：

 
{ 
    "foo" : "bar", 
    "blah" : [ 
    1, 
    2, 
    3 
    ] 
} 

设置SerializationFeature.INDENT_OUTPUT真只是插入新行字符而不是数组元素，用这种方式打印对象：

 
{ 
    "foo" : "bar", 
    "blah" : [1, 2, 3] 
} 

有没有人知道如何做到这一点？谢谢！

Answer 1

你可以扩展DefaultPrettyPrinter和覆盖的方法beforeArrayValues（...）和writeArrayValueSeparator（...）到archieve期望的行为。之后，您必须通过setPrettyPrinter(…)将您的新实现添加到您的JsonGenerator。

Answer 2

尝试JSON发电机...

API Reference
good example

Answer 3

多亏了有用的提示，我可以配置我ObjectMapper与所需的缩进如下：

private static class PrettyPrinter extends DefaultPrettyPrinter { 
    public static final PrettyPrinter instance = new PrettyPrinter(); 

    public PrettyPrinter() { 
     _arrayIndenter = Lf2SpacesIndenter.instance; 
    } 
} 

private static class Factory extends JsonFactory { 
    @Override 
    protected JsonGenerator _createGenerator(Writer out, IOContext ctxt) throws IOException { 
     return super._createGenerator(out, ctxt).setPrettyPrinter(PrettyPrinter.instance); 
    } 
} 

{ 
    ObjectMapper mapper = new ObjectMapper(new Factory()); 
    mapper.configure(SerializationFeature.INDENT_OUTPUT, true); 
} 

Answer 4

由OP谢天谢地提供的answer显示一种方式，获得单阵列 - 元素每行格式化JSON String来自writeValueAsString。基于这里的解决方案直接写入相同的格式化JSON与writeValue文件用更少的代码：

private static class PrettyPrinter extends DefaultPrettyPrinter { 
    public static final PrettyPrinter instance = new PrettyPrinter(); 

    public PrettyPrinter() { 
     _arrayIndenter = Lf2SpacesIndenter.instance; 
    } 
} 

{ 
    ObjectMapper mapper = new ObjectMapper(); 
    ObjectWriter writer = mapper.writer(PrettyPrinter.instance); 
    writer.writeValue(destFile, objectToSerialize); 
} 

Answer 5

如果你不希望延长DefaultPrettyPrinter你也可以只设置indentArraysWith属性外：

ObjectMapper objectMapper = new ObjectMapper(); 
objectMapper.enable(SerializationFeature.INDENT_OUTPUT); 

DefaultPrettyPrinter prettyPrinter = new DefaultPrettyPrinter(); 
prettyPrinter.indentArraysWith(DefaultPrettyPrinter.Lf2SpacesIndenter.instance); 

String json = objectMapper.writer(prettyPrinter).writeValueAsString(object);