【安全研究】Jackson 学习笔记）

基本介绍

Jackson框架是基于Java平台的一套数据处理工具，被称为\\”最好的Java Json解析器\\”，目前Jackson主要有1.x和2.x两个分支版本，其中1.x的类库中包命名以org.codehaus.jackson.xxx开头，2.x类库中包命令com.fastxml.jackson.xxx开头，Jackson框架包含以下3个核心库：

streaming
databind
annotations.Jackson

解析处理

ObjectMapper是Jackson库的主要类，它可以将JSON数据转换成Java对象或者将JAVA对象序列化为JSON数据，ObjectMapper通过JsonParser和JsonGenerator的实例实现JSON实际的读/写

类声明

org.codehaus.jackson.map.ObjectMapper类的声明如下：

public class ObjectMapper   extends ObjectCodec      implements Versioned

嵌套类

static class ObjectMapper.DefaultTypeResolverBuilder：定制TypeResolverBuilder，提供所谓的\\”默认输入\\”使用类型解析构建器

构造函数

ObjectMapper()：默认的构造函数，使用StdSerializerProvider作为其SerializerProvider，并使用BeanSerializerFactory作为其SerializerFactory
ObjectMapper(JsonFactory jf)：使用指定的JsonFactory构建必要的JsonParsers和/或JsonGenerators映射
ObjectMapper(JsonFactory jf, SerializerProvider sp, DeserializerProvider dp)
ObjectMapper(JsonFactory jf, SerializerProvider sp, DeserializerProvider dp, SerializationConfig sconfig, DeserializationConfig dconfig)
ObjectMapper(SerializerFactory sf)：可以设置序列化工厂setSerializerFactory(org.codehaus.jackson.map.SerializerFactory）

继承的方法

ObjectMapper类继承了java.lang.Objec类方法

数据处理

Json处理方法分类

Jackson支持Java对象与Json之间的相互转化，Java对象序列化为Json字符串，Json字符串也可以反序列化为相同的Java对象，Jackson提供了三种可选的Json处理方法：

树模型(Tree Model)：是最灵活的处理方式
流式API(Streaming API)：是效率最高的处理方式(开销低、读写速度快，但程序编写复杂度高)
数据绑定(Data Binding)：是最常用的处理方式

下面从结合具体的实战来看一下，首先在pom.xml文件中添加以下三个依赖：

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->    <dependency>      <groupId>com.fasterxml.jackson.core</groupId>      <artifactId>jackson-databind</artifactId>      <version>2.9.10</version>    </dependency>    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->    <dependency>      <groupId>com.fasterxml.jackson.core</groupId>      <artifactId>jackson-annotations</artifactId>      <version>2.9.10</version>    </dependency>
    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->    <dependency>      <groupId>com.fasterxml.jackson.core</groupId>      <artifactId>jackson-core</artifactId>      <version>2.9.10</version>    </dependency>

树模型(Tree Model)

tree model生成json

package com.jacksonTest;
import com.fasterxml.jackson.core.JsonFactory;import com.fasterxml.jackson.core.JsonGenerator;import com.fasterxml.jackson.databind.ObjectMapper;import com.fasterxml.jackson.databind.SerializationFeature;import com.fasterxml.jackson.databind.node.ArrayNode;import com.fasterxml.jackson.databind.node.JsonNodeFactory;import com.fasterxml.jackson.databind.node.ObjectNode;
import java.io.File;import java.io.FileWriter;
public class SerializationExampleTreeModel {    public static void main(String[] args) throws Exception {        //创建一个节点工厂,为我们提供所有节点        JsonNodeFactory factory = new JsonNodeFactory(false);        //创建一个json factory来写tree    modle为json        JsonFactory jsonFactory = new JsonFactory();        //创建一个json生成器        JsonGenerator generator = jsonFactory.createGenerator(new FileWriter(new File(\\\"country2.json\\\")));        //注意，默认情况下对象映射器不会指定根节点，下面设根节点为country        ObjectMapper mapper = new ObjectMapper();        ObjectNode country = factory.objectNode();
        country.put(\\\"country_id\\\", \\\"China\\\");        country.put(\\\"birthDate\\\", \\\"1949-10-01\\\");
        //在Java中，List和Array转化为json后对应的格式符号都是\\\"obj:[]\\\"        ArrayNode nation = factory.arrayNode();        nation.add(\\\"Han\\\").add(\\\"Meng\\\").add(\\\"Hui\\\").add(\\\"WeiWuEr\\\").add(\\\"Zang\\\");        country.set(\\\"nation\\\", nation);
        ArrayNode lakes = factory.arrayNode();        lakes.add(\\\"QingHai Lake\\\").add(\\\"Poyang Lake\\\").add(\\\"Dongting Lake\\\").add(\\\"Taihu Lake\\\");        country.set(\\\"lakes\\\", lakes);
        ArrayNode provinces = factory.arrayNode();        ObjectNode province = factory.objectNode();        ObjectNode province2 = factory.objectNode();        province.put(\\\"name\\\",\\\"Shanxi\\\");        province.put(\\\"population\\\", 37751200);        province2.put(\\\"name\\\",\\\"ZheJiang\\\");        province2.put(\\\"population\\\", 55080000);        provinces.add(province).add(province2);        country.set(\\\"provinces\\\", provinces);
        ObjectNode traffic = factory.objectNode();        traffic.put(\\\"HighWay(KM)\\\", 4240000);        traffic.put(\\\"Train(KM)\\\", 112000);        country.set(\\\"traffic\\\", traffic);
        mapper.configure(SerializationFeature.INDENT_OUTPUT, true);        mapper.writeTree(generator, country);    }}

程序运行生成country2.json：

{\\\"country_id\\\":\\\"China\\\",\\\"birthDate\\\":\\\"1949-10-01\\\",\\\"nation\\\":[\\\"Han\\\",\\\"Meng\\\",\\\"Hui\\\",\\\"WeiWuEr\\\",\\\"Zang\\\"],\\\"lakes\\\":[\\\"QingHai Lake\\\",\\\"Poyang Lake\\\",\\\"Dongting Lake\\\",\\\"Taihu Lake\\\"],\\\"provinces\\\":[{\\\"name\\\":\\\"Shanxi\\\",\\\"population\\\":37751200},{\\\"name\\\":\\\"ZheJiang\\\",\\\"population\\\":55080000}],\\\"traffic\\\":{\\\"HighWay(KM)\\\":4240000,\\\"Train(KM)\\\":112000}}

json反序列化为tree mode1

package com.jacksonTest;
import com.fasterxml.jackson.databind.JsonNode;import com.fasterxml.jackson.databind.ObjectMapper;import java.io.File;import java.util.Iterator;
public class DeserializationExampleTreeModel1 {    public static void main(String[] args) throws Exception {        ObjectMapper mapper = new ObjectMapper();        // Jackson提供一个树节点被称为\\\"JsonNode\\\",ObjectMapper提供方法来读json作为树的JsonNode根节点        JsonNode node = mapper.readTree(new File(\\\"country2.json\\\"));        // 看看根节点的类型        System.out.println(\\\"node JsonNodeType:\\\"+node.getNodeType());        // 是不是一个容器        System.out.println(\\\"node is container Node ? \\\"+node.isContainerNode());        // 得到所有node节点的子节点名称        System.out.println(\\\"---------得到所有node节点的子节点名称-------------------------\\\");        Iterator<String> fieldNames = node.fieldNames();        while (fieldNames.hasNext()) {            String fieldName = fieldNames.next();            System.out.print(fieldName+\\\" \\\");        }        System.out.println(\\\"\\\\n-----------------------------------------------------\\\");        // as.Text的作用是有值返回值，无值返回空字符串        JsonNode country_id = node.get(\\\"country_id\\\");        System.out.println(\\\"country_id:\\\"+country_id.asText() + \\\" JsonNodeType:\\\"+country_id.getNodeType());
        JsonNode birthDate = node.get(\\\"birthDate\\\");        System.out.println(\\\"birthDate:\\\"+birthDate.asText()+\\\" JsonNodeType:\\\"+birthDate.getNodeType());
        JsonNode nation = node.get(\\\"nation\\\");        System.out.println(\\\"nation:\\\"+ nation+ \\\" JsonNodeType:\\\"+nation.getNodeType());
        JsonNode lakes = node.get(\\\"lakes\\\");        System.out.println(\\\"lakes:\\\"+lakes+\\\" JsonNodeType:\\\"+lakes.getNodeType());
        JsonNode provinces = node.get(\\\"provinces\\\");        System.out.println(\\\"provinces JsonNodeType:\\\"+provinces.getNodeType());
        boolean flag = true;        for (JsonNode provinceElements : provinces) {            //为了避免provinceElements多次打印，用flag控制，打印能体现provinceElements的JsonNodeType就可以了            if(flag){                System.out.println(\\\"provinceElements JsonNodeType:\\\"+provinceElements.getNodeType());                System.out.println(\\\"provinceElements is container node? \\\"+provinceElements.isContainerNode());                flag = false;            }            Iterator<String> provinceElementFields = provinceElements.fieldNames();            while (provinceElementFields.hasNext()) {                String fieldName = (String) provinceElementFields.next();                String province;                if (\\\"population\\\".equals(fieldName)) {                    province = fieldName + \\\":\\\" + provinceElements.get(fieldName).asInt();                }else{                    province = fieldName + \\\":\\\" + provinceElements.get(fieldName).asText();                }                System.out.println(province);            }        }    }}

程序运行后打印结果如下：

【安全研究】Jackson 学习笔记）

json反序列化为tree mode2

再来看一下DeserializationExampleTreeModel2.java，本例中使用JsonNode.path的方法，path方法类似于DeserializationExampleTreeModel1.java中使用的get方法，但当node不存在时get方法返回null，而path返回MISSING类型的JsonNode

package com.jacksonTest;
import com.fasterxml.jackson.core.JsonProcessingException;import com.fasterxml.jackson.databind.JsonNode;import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;import java.io.IOException;import java.util.Iterator;
public class DeserializationExampleTreeModle2 {    public static void main(String[] args) throws JsonProcessingException, IOException {        ObjectMapper mapper = new ObjectMapper();        JsonNode node = mapper.readTree(new File(\\\"country2.json\\\"));        //path方法获取JsonNode时，当对象不存在时，返回MISSING类型的JsonNode        JsonNode missingNode = node.path(\\\"test\\\");        if(missingNode.isMissingNode()){            System.out.println(\\\"JsonNodeType : \\\" + missingNode.getNodeType());        }
        System.out.println(\\\"country_id:\\\"+node.path(\\\"country_id\\\").asText());
        JsonNode provinces = node.path(\\\"provinces\\\");        for (JsonNode provinceElements : provinces) {            Iterator<String> provincesFields = provinceElements.fieldNames();            while (provincesFields.hasNext()) {                String fieldName = (String) provincesFields.next();                String province;                if(\\\"name\\\".equals(fieldName)){                    province = fieldName +\\\":\\\"+ provinceElements.path(fieldName).asText();                }else{                    province = fieldName +\\\":\\\"+ provinceElements.path(fieldName).asInt();                }                System.out.println(province);            }        }    }}

程序运行打印结果：

【安全研究】Jackson 学习笔记）

流式API(Streaming API)

Stream生成json

package com.jacksonTest;
import com.fasterxml.jackson.core.JsonFactory;import com.fasterxml.jackson.core.JsonGenerator;
import java.io.File;import java.io.FileWriter;
public class StreamGeneratorJson {    public static void main(String[] args) throws Exception {        JsonFactory factory = new JsonFactory();        //从JsonFactory创建一个JsonGenerator生成器的实例        JsonGenerator generator = factory.createGenerator(new FileWriter(new File(\\\"country3.json\\\")));
        generator.writeStartObject();        generator.writeFieldName(\\\"country_id\\\");        generator.writeString(\\\"China\\\");        generator.writeFieldName(\\\"provinces\\\");        generator.writeStartArray();        generator.writeStartObject();        generator.writeStringField(\\\"name\\\", \\\"Shanxi\\\");        generator.writeNumberField(\\\"population\\\", 33750000);        generator.writeEndObject();        generator.writeEndArray();        generator.writeEndObject();        generator.close();    }}

程序运行后生成country3.json文件内容：

【安全研究】Jackson 学习笔记）

stream解析json

现在我们用Streaming API的方式来解析上面的Json,并查找json中population的值:

package com.jacksonTest;
import com.fasterxml.jackson.core.JsonFactory;import com.fasterxml.jackson.core.JsonParseException;import com.fasterxml.jackson.core.JsonParser;import com.fasterxml.jackson.core.JsonToken;
import java.io.File;import java.io.IOException;
public class StreamParserJson {    public static void main(String[] args) throws JsonParseException, IOException {        JsonFactory factory = new JsonFactory();        // 从JsonFactory创建JsonParser解析器的实例        JsonParser parser = factory.createParser(new File(\\\"country3.json\\\"));        while (!parser.isClosed()) {            // 得到一个token,第一次遍历时，token指向json文件中第一个符号\\\"{\\\"            JsonToken token = parser.nextToken();            if (token == null) {                break;            }            // 我们只查找 country3.json中的\\\"population\\\"字段的值，能体现解析的流程就可以了            // 当key是provinces时，我们进入provinces,查找population            if (JsonToken.FIELD_NAME.equals(token)&& \\\"provinces\\\".equals(parser.getCurrentName())) {                token = parser.nextToken();                if (!JsonToken.START_ARRAY.equals(token)) {                    break;                }                // 此时，token指向的应该是\\\"{\\\"                token = parser.nextToken();                if (!JsonToken.START_OBJECT.equals(token)) {                    break;                }                while (true) {                    token = parser.nextToken();                    if (token == null) {                        break;                    }                    if ( JsonToken.FIELD_NAME.equals(token)                            &&\\\"population\\\".equals(parser.getCurrentName())) {                        token = parser.nextToken();                        System.out.println(parser.getCurrentName() + \\\" : \\\"                                + parser.getIntValue());                    }                }            }        }    }}

程序运行后，在控制台打印结果如下：

【安全研究】Jackson 学习笔记）

数据绑定(Data Binding)

数据绑定简介

数据绑定API用于JSON转换和使用属性访问或使用注解POJO(普通Java对象)，以下是它的两个类型：

简单数据绑定 – 转换JSON，从Java Maps, Lists, Strings, Numbers, Booleans和null对象
完整数据绑定 – 转换JSON到任何JAVA类型

ObjectMapper读/写JSON两种类型的数据绑定，数据绑定是最方便的方式是类似XML的JAXB解析器

简单数据绑定

简单的数据绑定是指JSON映射到Java核心数据类型，下表列出了JSON类型和Java类型之间的关系：

【安全研究】Jackson 学习笔记）

具体代码示例：

package com.jacksonTest;
import com.fasterxml.jackson.core.JsonParseException;import com.fasterxml.jackson.databind.JsonMappingException;import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;import java.io.IOException;import java.util.HashMap;import java.util.Map;
public class JacksonTester {    public static void main(String args[]){        JacksonTester tester = new JacksonTester();        try {            ObjectMapper mapper = new ObjectMapper();
            Map<String,Object> studentDataMap = new HashMap<String,Object>();            int[] marks = {1,2,3};
            Student student = new Student();            student.setAge(10);            student.setName(\\\"Mahesh\\\");            // JAVA Object            studentDataMap.put(\\\"student\\\", student);            // JAVA String            studentDataMap.put(\\\"name\\\", \\\"Mahesh Kumar\\\");            // JAVA Boolean            studentDataMap.put(\\\"verified\\\", Boolean.FALSE);            // Array            studentDataMap.put(\\\"marks\\\", marks);
            mapper.writeValue(new File(\\\"student.json\\\"), studentDataMap);            //result student.json            //{            //   \\\"student\\\":{\\\"name\\\":\\\"Mahesh\\\",\\\"age\\\":10},            //   \\\"marks\\\":[1,2,3],            //   \\\"verified\\\":false,            //   \\\"name\\\":\\\"Mahesh Kumar\\\"            //}            studentDataMap = mapper.readValue(new File(\\\"student.json\\\"), Map.class);
            System.out.println(studentDataMap.get(\\\"student\\\"));            System.out.println(studentDataMap.get(\\\"name\\\"));            System.out.println(studentDataMap.get(\\\"verified\\\"));            System.out.println(studentDataMap.get(\\\"marks\\\"));        } catch (JsonParseException e) {            e.printStackTrace();        } catch (JsonMappingException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }}
class Student {    private String name;    private int age;    public Student(){}    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String toString(){        return \\\"Student [ name: \\\"+name+\\\", age: \\\"+ age+ \\\" ]\\\";    }}

运行结果如下所示：

【安全研究】Jackson 学习笔记）

完全数据绑定

完全数据绑定是指JSON映射到任何Java对象，例如：

//Create an ObjectMapper instanceObjectMapper mapper = new ObjectMapper();  
//map JSON content to Student objectStudent student = mapper.readValue(new File(\\\"student.json\\\"), Student.class);
//map Student object to JSON contentmapper.writeValue(new File(\\\"student.json\\\"), student);

具体代码示例：

package com.jacksonTest;
import com.fasterxml.jackson.core.JsonGenerationException;import com.fasterxml.jackson.core.JsonParseException;import com.fasterxml.jackson.databind.JsonMappingException;import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;import java.io.IOException;
public class JacksonTester {    public static void main(String args[]){        JacksonTester tester = new JacksonTester();        try {            Student student = new Student();            student.setAge(10);            student.setName(\\\"Mahesh\\\");            tester.writeJSON(student);
            Student student1 = tester.readJSON();            System.out.println(student1);
        } catch (JsonParseException e) {            e.printStackTrace();        } catch (JsonMappingException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }
    private void writeJSON(Student student) throws JsonGenerationException, JsonMappingException, IOException{        ObjectMapper mapper = new ObjectMapper();        mapper.writeValue(new File(\\\"student.json\\\"), student);    }
    private Student readJSON() throws JsonParseException, JsonMappingException, IOException{        ObjectMapper mapper = new ObjectMapper();        Student student = mapper.readValue(new File(\\\"student.json\\\"), Student.class);        return student;    }}
class Student {    private String name;    private int age;    public Student(){}    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String toString(){        return \\\"Student [ name: \\\"+name+\\\", age: \\\"+ age+ \\\" ]\\\";    }}

运行结果如下所示：

【安全研究】Jackson 学习笔记）

java对象序列化为json

Province.java：

package com.jacksonTest;
public class Province {    public String name;    public int population;    public String[] city;}

Country.java：

package com.jacksonTest;
import java.util.*;
public class Country {    // 注意：被序列化的bean的private属性字段需要创建getter方法或者属性字段应该为public    private String country_id;    private Date birthDate;    private List<String> nation = new ArrayList<String>();    private String[] lakes;    private List<Province> provinces = new ArrayList<Province>();    private Map<String, Integer> traffic = new HashMap<String, Integer>();        public Country() {        // TODO Auto-generated constructor stub    }
    public Country(String countryId) {        this.country_id = countryId;    }
    public String getCountry_id() {        return country_id;    }
    public void setCountry_id(String country_id) {        this.country_id = country_id;    }
    public Date getBirthDate() {        return birthDate;    }
    public void setBirthDate(Date birthDate) {        this.birthDate = birthDate;    }
    public List<String> getNation() {        return nation;    }
    public void setNation(List<String> nation) {        this.nation = nation;    }
    public String[] getLakes() {        return lakes;    }
    public void setLakes(String[] lakes) {        this.lakes = lakes;    }
    public Integer get(String key) {        return traffic.get(key);    }
    public Map<String, Integer> getTraffic() {        return traffic;    }
    public void setTraffic(Map<String, Integer> traffic) {        this.traffic = traffic;    }
    public void addTraffic(String key, Integer value) {        traffic.put(key, value);    }
    public List<Province> getProvinces() {        return provinces;    }
    public void setProvinces(List<Province> provinces) {        this.provinces = provinces;    }
    @Override    public String toString() {        return \\\"Country [country_id=\\\" + country_id + \\\", birthDate=\\\" + birthDate                + \\\", nation=\\\" + nation + \\\", lakes=\\\" + Arrays.toString(lakes)                + \\\", province=\\\" + provinces + \\\", traffic=\\\" + traffic + \\\"]\\\";    }}

JavaBeanSerializeToJson.java

package com.jacksonTest;
import com.fasterxml.jackson.annotation.JsonInclude;import com.fasterxml.jackson.databind.ObjectMapper;import com.fasterxml.jackson.databind.SerializationFeature;
import java.io.File;import java.text.SimpleDateFormat;import java.util.ArrayList;import java.util.List;
public class JavaBeanSerializeToJson {    public static void convert() throws Exception {        // 使用ObjectMapper来转化对象为Json        ObjectMapper mapper = new ObjectMapper();        // 添加功能，让时间格式更具有可读性        SimpleDateFormat dateFormat = new SimpleDateFormat(\\\"yyyy-MM-dd\\\");        mapper.setDateFormat(dateFormat);
        Country country = new Country(\\\"China\\\");        country.setBirthDate(dateFormat.parse(\\\"1949-10-01\\\"));        country.setLakes(new String[] { \\\"Qinghai Lake\\\", \\\"Poyang Lake\\\",                \\\"Dongting Lake\\\", \\\"Taihu Lake\\\"});
        List<String> nation = new ArrayList<String>();        nation.add(\\\"Han\\\");        nation.add(\\\"Meng\\\");        nation.add(\\\"Hui\\\");        nation.add(\\\"WeiWuEr\\\");        nation.add(\\\"Zang\\\");        country.setNation(nation);
        Province province = new Province();        province.name = \\\"Shanxi\\\";        province.population = 37751200;                Province province2 = new Province();        province2.name = \\\"ZheJiang\\\";        province2.population = 55080000;                List<Province> provinces = new ArrayList<Province>();        provinces.add(province);        provinces.add(province2);        country.setProvinces(provinces);
        country.addTraffic(\\\"Train(KM)\\\", 112000);        country.addTraffic(\\\"HighWay(KM)\\\", 4240000);        // 为了使JSON视觉上的可读性，增加一行如下代码，注意，在生产中不需要这样，因为这样会增大Json的内容        mapper.configure(SerializationFeature.INDENT_OUTPUT, true);        // 配置mapper忽略空属性        mapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);        // 默认情况，Jackson使用Java属性字段名称作为 Json的属性名称,也可以使用Jackson annotations(注解)改变Json属性名称        mapper.writeValue(new File(\\\"country.json\\\"), country);    }
    public static void main(String[] args) throws Exception {        convert();    }}

程序运行后生成country.json：

Json反序列化为java对象

package com.jacksonTest;
import com.fasterxml.jackson.databind.DeserializationFeature;import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;import java.text.SimpleDateFormat;import java.util.List;
public class JsonDeserializeToJava {    public static void main(String[] args) throws Exception {        //ObjectMapper类用序列化与反序列化映射器          ObjectMapper mapper = new ObjectMapper();        File json = new File(\\\"country.json\\\");        //当反序列化json时，未知属性会引起的反序列化被打断，这里我们禁用未知属性打断反序列化功能，          //因为，例如json里有10个属性，而我们的bean中只定义了2个属性，其它8个属性将被忽略          mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
        //从json映射到java对象，得到country对象后就可以遍历查找,下面遍历部分内容，能说明问题就可以了          Country country = mapper.readValue(json, Country.class);        System.out.println(\\\"country_id:\\\"+country.getCountry_id());        //设置时间格式，便于阅读          SimpleDateFormat dateformat = new SimpleDateFormat(\\\"yyyy-MM-dd\\\");        String birthDate = dateformat.format(country.getBirthDate());        System.out.println(\\\"birthDate:\\\"+birthDate);
        List<Province> provinces = country.getProvinces();        for (Province province : provinces) {            System.out.println(\\\"province:\\\"+province.name + \\\"\\\\n\\\" + \\\"population:\\\"+province.population);        }    }}

程序运行结果：

ObjectMapper使用特性

在默认情况下ObjectMapper在序列化时会将所有的字段逐一序列化，无论这些字段是否有值，或者为null，另外序列化依赖于getter方法，如果某个字段没有getter方法，那么该字段是不会被序列化的，由此可见在序列化时OjbectMapper是通过反射机制找到了对应的getter，然后将getter方法对应的字段序列化到Json中~

原创文章，作者：七芒星实验室，如若转载，请注明出处：https://www.sudun.com/ask/34164.html

【安全研究】Jackson 学习笔记）

基本介绍

解析处理

类声明

嵌套类

构造函数

继承的方法

数据处理

Json处理方法分类

树模型(Tree Model)

tree model生成json

json反序列化为tree mode2

流式API(Streaming API)

Stream生成json

stream解析json

数据绑定(Data Binding)

数据绑定简介

简单数据绑定

完全数据绑定

java对象序列化为json

ObjectMapper使用特性

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