Java如何使用Jackson JSON将JSON字符串转换为Map

我有以下代码：

public void testJackson() throws IOException {      ObjectMapper mapper = new ObjectMapper();     File from = new File("albumnList.txt");     TypeReference<HashMap<String,Object>> typeRef  = new TypeReference<HashMap<String,Object>>() {};    HashMap<String,Object> o = mapper.readValue(from, typeRef);     System.out.println("Got " + o); }   

它是从文件读取的，但

mapper.readValue()

InputStream

InputStream

new ByteArrayInputStream(astring.getBytes("UTF-8"));