我如何使用jackson像下面的示例那样创建json数组。
我尝试使用ObjectMapper,但这似乎不正确。
try (DirectoryStream<Path> ds = Files.newDirectoryStream(path)) {
for (Path file : ds) {
System.out.println("name:"+file.getFileName()+
"\n"+
"mime:"+Files.probeContentType(file)+
"\n"+
"locked:"+!Files.isWritable(file));
}
} catch (IOException e) {
System.err.println(e);
}
最终,我将制作一个具有以下值的json。
* - (int) size file size in b. required
* - (int) ts file modification time in unix time. required
* - (string) mime mimetype. required for folders, others - optionally
* - (bool) read read permissions. required
* - (bool) write write permissions. required
* - (bool) locked is object locked. optionally
* - (bool) hidden is object hidden. optionally
* - (string) alias for symlinks - link target path relative to root path. optionally
* - (string) target for symlinks - link target path. optionally
这是我提供的一个示例json。
"files": [
{
"mime": "directory",
"ts": 1334071677,
"read": 1,
"write": 0,
"size": 0,
"hash": "l1_Lw",
"volumeid": "l1_",
"name": "Demo",
"locked": 1,
"dirs": 1
},
{
"mime": "directory",
"ts": 1334071677,
"read": 1,
"write": 0,
"size": 0,
"hash": "l1_Lw",
"volumeid": "l1_",
"name": "Demo",
"locked": 1,
"dirs": 1
},
{
"mime": "directory",
"ts": 1340114567,
"read": 0,
"write": 0,
"size": 0,
"hash": "l1_QmFja3Vw",
"name": "Backup",
"phash": "l1_Lw",
"locked": 1
},
{
"mime": "directory",
"ts": 1310252178,
"read": 1,
"write": 0,
"size": 0,
"hash": "l1_SW1hZ2Vz",
"name": "Images",
"phash": "l1_Lw",
"locked": 1
},
{
"mime": "application\/x-genesis-rom",
"ts": 1310347586,
"read": 1,
"write": 0,
"size": 3683,
"hash": "l1_UkVBRE1FLm1k",
"name": "README.md",
"phash": "l1_Lw",
"locked": 1
}
]
编辑1
Map<String, Object> filesMap = new HashMap<>();
List<Object> files = new ArrayList<Object>();
System.out.println("\nNo filter applied:");
try (DirectoryStream<Path> ds = Files.newDirectoryStream(path)) {
for (Path file : ds) {
Map<String, Object> fileInfo = new HashMap<>();
fileInfo.put("name", file.getFileName().toString());
// Prints Files in Director
// Files.getAttribute(file,"size");
System.out.println("name:" + file.getFileName().toString() +
"\n" +
"mime:" + Files.probeContentType(file) +
"\n" +
"locked:" + !Files.isWritable(file));
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(fileInfo);
files.add(json);
}
} catch (IOException e) {
System.err.println(e);
}
files.toArray();
filesMap.put("files", files);
ObjectMapper mapper = new ObjectMapper();
String jsonString;
try {
jsonString = mapper.writeValueAsString(filesMap);
} catch (IOException e) {
jsonString = "fail"; //To change body of catch statement use File | Settings | File Templates.
}
提出以下更接近的json,但我不知道为什么在{}之前和之后加引号。
{"files":["{\"name\":\"32C92124-EFCF-42C1-AFD2-8B741AE6854B.jpg\"}","{\"name\":\"58D5B83F-4065-4D6E-92BE-8181D99CB6CB.jpg\"}","{\"name\":\"7B1464A0-FBA1-429E-8A39-3DE5B539FBF8.jpg\"}","{\"name\":\"888159CF-45BE-475F-8C6A-64B3E1D97278.jpg\"}"]}
最终答案
Map<String, Object> filesMap = new HashMap<>();
List<Object> files = new ArrayList<Object>();
System.out.println("\nNo filter applied:");
try (DirectoryStream<Path> ds = Files.newDirectoryStream(path)) {
for (Path file : ds) {
Map<String, Object> fileInfo = new HashMap<>();
fileInfo.put("name", file.getFileName().toString());
System.out.println("name:" + file.getFileName().toString() +
"\n" +
"mime:" + Files.probeContentType(file) +
"\n" +
"locked:" + !Files.isWritable(file));
files.add(fileInfo);
}
} catch (IOException e) {
System.err.println(e);
}
files.toArray();
filesMap.put("files", files);
ObjectMapper mapper = new ObjectMapper();
String jsonString;
try {
jsonString = mapper.writeValueAsString(filesMap);
} catch (IOException e) {
jsonString = "fail";
}
您需要一个JsonNodeFactory
:
final JsonNodeFactory factory = JsonNodeFactory.instance;
此类具有创建ArrayNode
s,ObjectNode
s,IntNode
s,DecimalNode
s,TextNode
s和诸如此类的方法。ArrayNode
s和ObjectNode
s具有便捷的变异方法,可以直接添加大多数JSON原语(非容器)值,而不必经过工厂(当然,在内部,它们引用此工厂,这就是原因)。
关于ObjectMapper
,请注意,它既是串行器(ObjectWriter
),也是解串器(ObjectReader
)。
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我来说两句