Java中Jackson库操作json的基本操作
这段工作中总会遇到使用Java处理JSON的情况，大部分都使用的是开源工具Jackson实现的。因此总结一下发上来，希望对看到的人有所帮助。
上一篇文档中，我已经讲过Java如何使用Jackson来对Json进行序列化，这边我再稍微回顾一下。
Jackson中有个ObjectMapper类很是实用，用于Java对象与JSON的互换。
1、Java对象转换为JSON：
User user=new User(); //Java Object
ObjectMapper mapper = new ObjectMapper();
mapper.writeValueAsString(user); //返回字符串
//输出格式化后的字符串(有性能损耗)
mapper.defaultPrettyPrintingWriter().writeValueAsString(user);
mapper.writeValue(new File("c:\\user.json"), user); //指定文件写入
//设置序列化配置(全局),设置序列化时不输出空值.
sharedMapper.getSerializationConfig().setSerializationInclusion(Inclusion.NON_NULL);
2、JSON反序列化为Java对象：
ObjectMapper mapper = new ObjectMapper();
//解析器支持解析单引号
mapper.configure(Feature.ALLOW_SINGLE_QUOTES,true);
//解析器支持解析结束符
mapper.configure(Feature.ALLOW_UNQUOTED_CONTROL_CHARS,true);
HashMap jsonMap = mapper.readValue(json,HashMap.class); //转换为HashMap对象
下面讲解一下Jackson对Json的基本操作：
Map转换为json
package com.pcmall;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
public class Map2Json {
/**
* 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)
{
}
}
public static void main(String[] args){
MyTest01();
}
}
输出结果如下：
123abc "zhang"
解析json格式字符串
package com.pcmall;
import java.io.IOException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
public class ResolveJson {
/**
* 解析 json 格式字符串
*/
public static void MyTest02()
{
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)
{
}
}
public static void main(String[] args){
MyTest02();
}
}
输出结果如下：
7 6 ok
json直接提取值
package com.pcmall;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
public class GetPartJson {
/**
* json 直接提取 值
*/
public static void MyTest03()
{
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)
{
}
}
public static void main(String[] args){
MyTest03();
}
}
输出结果如下：
4
"288206077664983"
1371052476
"297031120529307"
1370751789
{"id":"288206077664983","timestamp":1371052476}
{"id":"186983078111768","timestamp":1370944068}
{"id":"297031120529307","timestamp":1370751789}
{"id":"273831022294863","timestamp":1369994812}
创建一个Json，并向该json添加内容
package com.pcmall;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
public class CreateJson {
/**
* 创建一个 json，并向该 json 添加内容
*/
public static void MyTest04()
{
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));
// 得到的输出信息
// {"child":{"nodekey1":1,"nodekey2":2},"arraynode":[{"nodekey1":1,"nodekey2":2},1]}
}
catch (Exception e)
{
}
}
public static void main(String[] args){
MyTest04();
}
}
输出结果如下：
{"nodekey1":1,"nodekey2":2}
{"child":{"nodekey1":1,"nodekey2":2},"arraynode":[{"nodekey1":1,"nodekey2":2},1]}
创建一个array node
package com.pcmall;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
public class CreateNodeArray {
// 创建一个 array node
public static void MyTest05()
{
try
{
ObjectMapper mapper = new ObjectMapper();
ArrayNode arrayNode = mapper.createArrayNode();
int i = 0;
// 在 array 内创建 3 组 node 存入 array
for (i = 0; i < 3; i++)
{
// 创建一个 node
ObjectNode node = mapper.createObjectNode();
node.put("nodeA", i);
node.put("nodeB", i);
node.put("nodeC", i);
// 向 array 内添 node
arrayNode.add(node);
}
// 根
ObjectNode root = mapper.createObjectNode();
root.put("total", i);
root.put("rows", arrayNode);
System.out.println(mapper.writeValueAsString(root));
// 得到的输出信息
// {"total":3,"rows":[{"nodeA":0,"nodeB":0,"nodeC":0},{"nodeA":1,"nodeB":1,"nodeC":1},{"nodeA":2,"nodeB":2,"nodeC":2}]}
}
catch (Exception e)
{
e.printStackTrace();
}
}
public static void main(String[] args){
MyTest05();
}
}
输出结果如下：
{"total":3,"rows":[{"nodeA":0,"nodeB":0,"nodeC":0},{"nodeA":1,"nodeB":1,"nodeC":1},{"nodeA":2,"nodeB":2,"nodeC":2}]}
在添加 array 节点时，put node 的方法已经过时，将使用 set 方法 添加 array 节点，举例：
root.set ("rows", arrayNode);
实际工作中应用
使用Firefox的RESTClient插件进行测试，输入URL，输出如下图所示的结果。
其中基础类如下：
import java.util.Date;
public class SaleOrderItem {
private String spxx01;
private String spxx04;
private float lsdi05;
private Date lsdi11;
private long lsd01;
private long lsdi01;
private float lsdi02;
private String gsxx01;
public String getSpxx01() {
return spxx01;
}
public void setSpxx01(String spxx01) {
this.spxx01 = spxx01;
}
public String getSpxx04() {
return spxx04;
}
public void setSpxx04(String spxx04) {
this.spxx04 = spxx04;
}
public float getLsdi05() {
return lsdi05;
}
public void setLsdi05(float lsdi05) {
this.lsdi05 = lsdi05;
}
public Date getLsdi11() {
return lsdi11;
}
public void setLsdi11(Date lsdi11) {
this.lsdi11 = lsdi11;
}
public long getLsd01() {
return lsd01;
}
public void setLsd01(long lsd01) {
this.lsd01 = lsd01;
}
public long getLsdi01() {
return lsdi01;
}
public void setLsdi01(long lsdi01) {
this.lsdi01 = lsdi01;
}
public float getLsdi02() {
return lsdi02;
}
public void setLsdi02(float lsdi02) {
this.lsdi02 = lsdi02;
}
public String getGsxx01() {
return gsxx01;
}
public void setGsxx01(String gsxx01) {
this.gsxx01 = gsxx01;
}
@Override
public String toString(){
return spxx04;
}
}
业务类使用Spring RestTemplate解析RESTful服务获取到Json，然后调用ObjectMapper对象mapper的readValue(String,TypeReference)方法获取到SaleOrderItem列表。
代码如下 ：
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.springframework.web.client.RestClientException;
import org.springframework.web.client.RestTemplate;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
public class RestWebservice {
/**
* @param args
* @throws IOException
* @throws JsonProcessingException
* @throws Exception
* @throws RestClientException
*/
public static void main(String[] args) throws JsonProcessingException, IOException{
RestTemplate restTemplate = new RestTemplate();
//get方式***********************************************************************************************************
//参数直接放在URL中
String message = restTemplate.getForObject("http://xxx.xxx.xxx.xxx:8080/pad/interface/poslsd/saleOrderDetail?saleOrder=5078603&gsxx=0001", String.class );
System.out.println(message);
List<SaleOrderItem> saleOrderItems = new ArrayList<SaleOrderItem>();
ObjectMapper mapper = new ObjectMapper();
JsonNode root = mapper.readTree(message);
JsonNode data = root.path("data");
String strData = data.toString();
if(data.isArray()){
saleOrderItems = mapper.readValue(strData, new TypeReference<List<SaleOrderItem>>(){});
System.out.println(saleOrderItems.size());
for(SaleOrderItem item : saleOrderItems){
System.out.println(item);
}
}
}
}
输出结果如下：
{"code":10001,"message":"操作成功","total":1,"data":[{"spxx01":97321,"spxx04":"同方商用主机超越Z400","lsdi05":1.0,"lsdi11":1460044800000,"lsd01":5078603,"lsdi01":507860301,"lsdi02":2999.0,"gsxx01":"0001"}]}
1
同方商用主机超越Z400