Maven下使用Jackson

1.添加依赖：

2 com.fasterxml.jackson.databind.ObjectMapper在Jackson Databind中。ObjectMapper可以从String，File，InputStream，URL（json数据的格式），自定义的Java类中读取JSON，ObjectMapper中的重载方法readValue()实现了这些功能。下面看从String读取；

public static void readFromString(){

String carJson =  "{ \"brand\" : \"Mercedes\"," +

"  \"doors\" : 5," +

"  \"owners\" : [\"John\", \"Jack\", \"Jill\"]," +

"  \"nestedObject\" : { \"field\" : \"value\" } }";

ObjectMapper objectMapper = new ObjectMapper();

try {

// Read JSON from a Reader instance.

//            Reader reader = new StringReader(carJson);

//            JsonNode node = objectMapper.readValue(reader, JsonNode.class);

JsonNode node = objectMapper.readValue(carJson, JsonNode.class);

JsonNode brandNode = node.get("brand");

String brand = brandNode.asText();

System.out.println("brand = " + brand);

JsonNode doorsNode = node.get("doors");

Integer doors = doorsNode.asInt();

System.out.println("doors = " + doors);

JsonNode owners = node.get("owners");

JsonNode johnNode = owners.get(0);

String owner = johnNode.asText();

System.out.println("john = " + owner);

JsonNode nestNode = node.get("nestedObject");

JsonNode fieldNode = nestNode.get("field");

String field = fieldNode.asText();

System.out.println("field = " + field);

}

catch (Exception e){

e.printStackTrace();

}

}