Java操作JSON数据(4,end)--Jackson操作JSON数据，
Jackson是SpringBoot默认使用的JSON处理库，它可以轻松的将Java对象转换成JSON对象，同样也可以将JSON转换成Java对象。本文介绍下Jackson的基本使用方法，包括序列化和反序列化；文中所使用到的软件版本：Java 1.8.0_191、Jackson 2.10.0。
1、引入依赖
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.10.0</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.10.0</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.10.0</version>
</dependency>
如果使用的是SpringBoot，默认就使用了Jackson，则无需引入。
2、序列化
public static String serialize() {
MyBean bean = new MyBean();
bean.setS("测试字符串");
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.HOUR_OF_DAY, -1);
bean.setD(calendar.getTime());
List<MyBean> list = new ArrayList<MyBean>();
list.add(bean);
Map<String, List<MyBean>> map = new HashMap<String, List<MyBean>>();
map.put("data", list);
String result = "";
try {
ObjectMapper objectMapper = new ObjectMapper();
//设置日期格式，也可在类属性上使用@JsonFormat(pattern="yyyy-MM-dd HH:mm:ss")来设置
objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
objectMapper.setSerializationInclusion(Include.ALWAYS);
//字符串如果为null则输出""
objectMapper.setSerializerFactory(objectMapper.getSerializerFactory().withSerializerModifier(new BeanSerializerModifier() {
@Override
public List<BeanPropertyWriter> changeProperties(SerializationConfig config, BeanDescription beanDesc, List<BeanPropertyWriter> beanProperties) {
for (BeanPropertyWriter writer : beanProperties) {
Class<?> clazz = writer.getType().getRawClass();
if (CharSequence.class.isAssignableFrom(clazz) || Character.class.isAssignableFrom(clazz)) {
writer.assignNullSerializer(new JsonSerializer<Object>() {
@Override
public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
jsonGenerator.writeString("");
}
});
}
}
return beanProperties;
}
}));
result = objectMapper.writeValueAsString(map);
System.out.println(result);
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
3、反序列化
public static void deserialize() {
String s = serialize();
try {
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
TypeReference<Map<String, List<MyBean>>> type = new TypeReference<Map<String, List<MyBean>>>(){};
Map<String, List<MyBean>> map = objectMapper.readValue(s, type);
System.out.println(map);
//树模型api
JsonNode root = objectMapper.readTree(s);
JsonNode bean = root.get("data").get(0);
System.out.println(bean.get("s").asText());
//...
} catch (Exception e) {
e.printStackTrace();
}
}
4、完整例子
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package com.inspur.demo.json;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationConfig;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;
import com.fasterxml.jackson.databind.ser.BeanSerializerModifier;
/**
* Jackson操作JSON数据
*/
public class JacksonCase {
/**
* 序列化
*/
public static String serialize() {
MyBean bean =
new MyBean();
bean.setS("测试字符串"
);
Calendar calendar =
Calendar.getInstance();
calendar.add(Calendar.HOUR_OF_DAY, -1
);
bean.setD(calendar.getTime());
List<MyBean> list =
new ArrayList<MyBean>
();
list.add(bean);
Map<String, List<MyBean>> map =
new HashMap<String, List<MyBean>>
();
map.put("data"
, list);
String result = ""
;
try {
ObjectMapper objectMapper =
new ObjectMapper();
//设置日期格式，也可在类属性上使用@JsonFormat(pattern="yyyy-MM-dd HH:mm:ss")来设置
objectMapper.setDateFormat(
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"
));
objectMapper.setSerializationInclusion(Include.ALWAYS);
//字符串如果为null则输出""
objectMapper.setSerializerFactory(objectMapper.getSerializerFactory().withSerializerModifier(
new BeanSerializerModifier() {
@Override
public List<BeanPropertyWriter> changeProperties(SerializationConfig config, BeanDescription beanDesc, List<BeanPropertyWriter>
beanProperties) {
for (BeanPropertyWriter writer : beanProperties) {
Class<?> clazz =
writer.getType().getRawClass();
if (CharSequence.
class.isAssignableFrom(clazz) || Character.
class.isAssignableFrom(clazz)) {
writer.assignNullSerializer(new JsonSerializer<Object>
() {
@Override
public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider)
throws IOException {
jsonGenerator.writeString(""
);
}
});
}
}
return beanProperties;
}
}));
result =
objectMapper.writeValueAsString(map);
System.out.println(result);
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
/**
* 反序列化
*/
public static void deserialize() {
String s =
serialize();
try {
ObjectMapper objectMapper =
new ObjectMapper();
objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"
));
TypeReference<Map<String, List<MyBean>>> type =
new TypeReference<Map<String, List<MyBean>>>
(){};
Map<String, List<MyBean>> map =
objectMapper.readValue(s, type);
System.out.println(map);
//树模型api
JsonNode root =
objectMapper.readTree(s);
JsonNode bean = root.get("data").get(0
);
System.out.println(bean.get("s"
).asText());
//...
}
catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
serialize();
deserialize();
}
}
JacksonCase
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package com.inspur.demo.json;
import java.util.Arrays;
import java.util.Date;
public class MyBean {
private String s = "字符串"
;
private String s2;
private String s3 = "字符串3"
;
private int i = 123
;
private Integer i2;
private char c = '到'
;
private char[] c2 =
new char[]{'a', 'b'
};
private Date d =
new Date();
private Date[] d2 =
new Date[]{
new Date(),
new Date()};
public String getS() {
return s;
}
public void setS(String s) {
this.s =
s;
}
public String getS2() {
return s2;
}
public void setS2(String s2) {
this.s2 =
s2;
}
public String getS3() {
return s3;
}
public void setS3(String s3) {
this.s3 =
s3;
}
public int getI() {
return i;
}
public void setI(
int i) {
this.i =
i;
}
public Integer getI2() {
return i2;
}
public void setI2(Integer i2) {
this.i2 =
i2;
}
public char getC() {
return c;
}
public void setC(
char c) {
this.c =
c;
}
public char[] getC2() {
return c2;
}
public void setC2(
char[] c2) {
this.c2 =
c2;
}
public Date getD() {
return d;
}
public void setD(Date d) {
this.d =
d;
}
public Date[] getD2() {
return d2;
}
public void setD2(Date[] d2) {
this.d2 =
d2;
}
@Override
public String toString() {
return "MyBean [s=" + s + ", s2=" + s2 + ", s3=" + s3 + ", i=" + i + ", i2=" + i2 + ", c=" + c + ", c2="
+ Arrays.toString(c2) + ", d=" + d + ", d2=" + Arrays.toString(d2) + "]"
;
}
}
MyBean
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