代码提升篇-JSON库详细解析

User user = new User();
user.setName("校长");
user.setAge(3);
user.setSalary(new BigDecimal("123456789.0123"));
String jsonString = JSON.toJSONString(user);
System.out.println(jsonString);
// 输出 {"age":3,"name":"校长","old":false,"salary":123456789.0123}

String jsonString = "{\"age\":3,\"birthdate\":1496738822842,\"name\":\"校长\",\"old\":true,\"salary\":123456789.0123}";
 User u = JSON.parseObject(jsonString ,User.class);
 System.out.println(u.getName());
 // 输出 校长

String jsonStringArray = "[{\"age\":3,\"birthdate\":1496738822842,\"name\":\"校长\",\"old\":true,\"salary\":123456789.0123}]";
List<User> userList = JSON.parseArray(jsonStringArray, User.class);
System.out.println(userList.size());
// 输出 1

JSON.defaultTimeZone = TimeZone.getTimeZone("Asia/Shanghai");
JSON.defaultLocale = Locale.US;
        
public static class Model {
    @JSONField(format = "MMM dd, yyyy h:mm:ss aa")
    private java.util.Date date;

    public java.util.Date getDate() {
        return date;
    }

    public void setDate(java.util.Date date) {
        this.date = date;
    }

    @JSONField(format = "MMM-dd-yyyy h:mm:ss aa")
    public java.sql.Date date2;
}

public class A {
    @JSONField(name="ID")
    private int id;

    public int getId() {return id;}
    public void setId(int value) {this.id = id;}
}

public class A {
    @JSONField(serialize=false)
    public Date date;
}

public class A {
    @JSONField(deserialize=false)
    public Date date;
}

public static class VO {
    @JSONField(ordinal = 3)
    private int f0;

    @JSONField(ordinal = 2)
    private int f1;

    @JSONField(ordinal = 1)
    private int f2;
}

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.10.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.10.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.10.1</version>
</dependency>

public void toJson() throws JsonProcessingException {

    ObjectMapper mapper = new ObjectMapper();

    City case1 = new City();
    case1.setCity("SZ");
    case1.setAge(123);

    String jsonStr = mapper.writeValueAsString(case1);
    System.out.println("JSON:" + jsonStr);
}
// 输出：JSON:{"city":"SZ","age":123}

public void toObj() throws JsonParseException, JsonMappingException, IOException {
    ObjectMapper mapper = new ObjectMapper();
    String inputjsonstr = "{\"city\":\"SZ\",\"age\":123}";
    
    City readcase = mapper.readValue(inputjsonstr, City.class);

    System.out.println("city info:" + readcase);
}

mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);

// 基础类型
Gson gson = new Gson();
gson.toJson(1);            ==> prints 1
gson.toJson("abcd");       ==> prints "abcd"
gson.toJson(new Long(10)); ==> prints 10
int[] values = { 1 };
gson.toJson(values);       ==> prints [1]

// 对象
BagOfPrimitives obj = new BagOfPrimitives();
Gson gson = new Gson();
String json = gson.toJson(obj);  
==> json is {"value1":1,"value2":"abc"}

// 数组
Gson gson = new Gson();
int[] ints = {1, 2, 3, 4, 5};
String[] strings = {"abc", "def", "ghi"};
gson.toJson(ints);     ==> prints [1,2,3,4,5]
gson.toJson(strings);  ==> prints ["abc", "def", "ghi"]

// 集合
Gson gson = new Gson();
Collection<Integer> ints = Lists.immutableList(1,2,3,4,5);
String json = gson.toJson(ints); ==> json is [1,2,3,4,5]

class BagOfPrimitives {
  private int value1 = 1;
  private String value2 = "abc";
  private transient int value3 = 3;
  BagOfPrimitives() {
    // no-args constructor
  }
}

// 基础类型
Gson gson = new Gson();
int one = gson.fromJson("1", int.class);
Integer one = gson.fromJson("1", Integer.class);
Long one = gson.fromJson("1", Long.class);
Boolean false = gson.fromJson("false", Boolean.class);
String str = gson.fromJson("\"abc\"", String.class);
String anotherStr = gson.fromJson("[\"abc\"]", String.class);

// 对象
BagOfPrimitives obj2 = gson.fromJson(json, BagOfPrimitives.class);   
==> obj2 is just like obj

// 数组
Gson gson = new Gson();
int[] ints2 = gson.fromJson("[1,2,3,4,5]", int[].class); 
==> ints2 will be same as ints

// 集合
Gson gson = new Gson();
Type collectionType = new TypeToken<Collection<Integer>>(){}.getType();
Collection<Integer> ints2 = gson.fromJson(json, collectionType);
ints2 is same as ints

GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapter(MyType2.class, new MyTypeAdapter());
gson.registerTypeAdapter(MyType.class, new MySerializer());
gson.registerTypeAdapter(MyType.class, new MyDeserializer());
gson.registerTypeAdapter(MyType.class, new MyInstanceCreator());