java Jackson 库操作 json 的基本演示

核心库下载地址

http://repo1.maven.org/maven2/com/fasterxml/jackson/core/

jackson-annotations-2.2.2.jar

jackson-core-2.2.2.jar

jackson-databind-2.2.2.jar

文件类型支持模块

http://repo1.maven.org/maven2/com/fasterxml/jackson/dataformat/

jackson-dataformat-xml-2.2.2.jar

导入库

import com.fasterxml.jackson.databind.ObjectMapper;

import com.fasterxml.jackson.databind.JsonNode;

import com.fasterxml.jackson.databind.JsonMappingException;

import com.fasterxml.jackson.databind.node.ObjectNode;

import com.fasterxml.jackson.databind.node.ArrayNode;

import com.fasterxml.jackson.core.JsonGenerator;

import com.fasterxml.jackson.core.JsonEncoding;

import com.fasterxml.jackson.core.JsonParseException;

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/**

* Map 转换为 json

*/

public static void MyTest01()

{

Map<String, String> hashMap = new HashMap<String, String>();

hashMap.put("name", "zhang");

hashMap.put("sex", "1");

hashMap.put("login", "Jack");

hashMap.put("password", "123abc");

try

{

ObjectMapper objectMapper = new ObjectMapper();

String userMapJson = objectMapper.writeValueAsString(hashMap);

JsonNode node = objectMapper.readTree(userMapJson);

// 输出结果转意，输出正确的信息

System.out.println(node.get("password").asText());

// 输出不转意,输出结果会包含""，这是不正确的，除非作为json传递，如果是输出结果值，必须如上一行的操作

System.out.println(node.get("name"));

}

catch (IOException e)

{

}

}

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/**

* 解析 json 格式字符串

*/

public static void MyTest03()

{

try

{

String str = "{\"data\":{\"birth_day\":7,\"birth_month\":6},\"errcode\":0,\"msg\":\"ok\",\"ret\":0}";

ObjectMapper mapper = new ObjectMapper();

JsonNode root = mapper.readTree(str);

JsonNode data = root.path("data");

JsonNode birth_day = data.path("birth_day");

System.out.println(birth_day.asInt());

JsonNode birth_month = data.path("birth_month");

System.out.println(birth_month.asInt());

JsonNode msg = root.path("msg");

System.out.println(msg.textValue());

}

catch (IOException e)

{

}

}

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/**

* json 直接提取 值

*/

public static void MyTest05()

{

try

{

// 演示字符串

String str = "{\"data\":{\"hasnext\":0,\"info\":[{\"id\":\"288206077664983\",\"timestamp\":1371052476},{\"id\":\"186983078111768\",\"timestamp\":1370944068},{\"id\":\"297031120529307\",\"timestamp\":1370751789},{\"id\":\"273831022294863\",\"timestamp\":1369994812}],\"timestamp\":1374562897,\"totalnum\":422},\"errcode\":0,\"msg\":\"ok\",\"ret\":0,\"seqid\":5903702688915195270}";

ObjectMapper mapper = new ObjectMapper();

JsonNode root = mapper.readTree(str);

// 提取 data

JsonNode data = root.path("data");

// 提取 info

JsonNode info = data.path("info");

System.out.println(info.size());

// 得到 info 的第 0 个

JsonNode item = info.get(0);

System.out.println(item.get("id"));

System.out.println(item.get("timestamp"));

// 得到 info 的第 2 个

item = info.get(2);

System.out.println(item.get("id"));

System.out.println(item.get("timestamp"));

// 遍历 info 内的 array

if (info.isArray())

{

for (JsonNode objNode : info)

{

System.out.println(objNode);

}

}

}

catch (Exception e)

{

}

}

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/**

* 创建一个 json，并向该 json 添加内容

*/

public static void MyTest07()

{

try

{

ObjectMapper mapper = new ObjectMapper();

ObjectNode root1 = mapper.createObjectNode();

root1.put("nodekey1", 1);

root1.put("nodekey2", 2);

System.out.println(root1.toString());

//Create the root node

ObjectNode root = mapper.createObjectNode ();

//Create a child node

ObjectNode node1 = mapper.createObjectNode ();

node1.put ("nodekey1", 1);

node1.put ("nodekey2", 2);

//Bind the child nodes

root.put ("child", node1);

//Array of nodes

ArrayNode arrayNode = mapper.createArrayNode ();

arrayNode.add (node1);

arrayNode.add (1);

//Bind array node

root.put ("arraynode", arrayNode);

System.out.println (mapper.writeValueAsString (root));

}

catch (Exception e)

{

}

}

json转为map

ObjectMapper mapper = new ObjectMapper();

String json = (String) configMap.get(key);

try {

Map<String,Object> productMap = mapper.readValue(json,Map.class);

//如果是范围的话先不转换

value = (String) productMap.get(value)==null ? value : (String)productMap.get(value);

参考资料

http://wiki.fasterxml.com/JacksonInFiveMinutes

blog.csdn.net/joyous/article/details/9448461

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