ObjectMapper

小咪咪 2022-07-12 04:25 100阅读 0赞

ObjectMapper类是Jackson库的主要类。它提供一些功能将转换成Java对象匹配JSON结构，反之亦然。它使用JsonParser和JsonGenerator的实例实现JSON实际的读/写。

## 类声明 ##

以下是org.codehaus.jackson.map.ObjectMapper类的声明：

public class ObjectMapper
       extends ObjectCodec
          implements Versioned

## 嵌套类 ##

## 构造函数 ##

<table style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:14px; border-collapse:collapse; border-spacing:0px; max-width:100%; margin:8px 0px; padding:0px; border-color:rgb(214,214,214); vertical-align:top; color:rgb(49,49,49); line-height:22px; width:604px; background-color:rgb(247,247,247)"> 
 <tbody style="font-size:16px"> 
  <tr style=""> 
   <th style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; margin:0px; border-collapse:collapse; border:1px solid rgb(214,214,214); line-height:1.42857; vertical-align:top; width:38px; background:rgb(238,238,238)"> S.N.</th> 
   <th style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; margin:0px; border-collapse:collapse; border:1px solid rgb(214,214,214); line-height:1.42857; vertical-align:top; background:rgb(238,238,238)"> 构造函数 &amp; 描述</th> 
  </tr> 
  <tr style=""> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> 1</td> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> <span style="font-size:16px; font-weight:700">ObjectMapper()</span><br style="font-size:16px"> 默认的构造函数，这将构建默认JsonFactory必要时使用StdSerializerProvider作为其SerializerProvider，并BeanSerializerFactory作为其SerializerFactory。</td> 
  </tr> 
  <tr style=""> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> 2</td> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> <span style="font-size:16px; font-weight:700">ObjectMapper(JsonFactory jf)</span><br style="font-size:16px"> 构造使用指定的JsonFactory构建必要的JsonParsers和/或JsonGenerators映射。</td> 
  </tr> 
  <tr style=""> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> 3</td> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> <span style="font-size:16px; font-weight:700">ObjectMapper(JsonFactory jf, SerializerProvider sp, DeserializerProvider dp)</span></td> 
  </tr> 
  <tr style=""> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> 4</td> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> <span style="font-size:16px; font-weight:700">ObjectMapper(JsonFactory jf, SerializerProvider sp, DeserializerProvider dp, SerializationConfig sconfig, DeserializationConfig dconfig)</span></td> 
  </tr> 
  <tr style=""> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> 5</td> 
   <td style="font-family:'Open Sans',Arial,'Hiragino Sans GB','Microsoft YaHei',微软雅黑,STHeiti,'WenQuanYi Micro Hei',SimSun,sans-serif,sans-serif; font-size:11pt; padding:5px; line-height:1.42857; vertical-align:top; border:1px solid rgb(214,214,214); border-collapse:collapse"> <span style="font-size:16px; font-weight:700">ObjectMapper(SerializerFactory sf)</span><br style="font-size:16px"> 不推荐使用。使用其他构造来代替; 注意，可以设置序列化工厂setSerializerFactory（org.codehaus.jackson.map.SerializerFactory）</td> 
  </tr> 
 </tbody> 
</table>

## 继承的方法 ##

这个类继承了以下类方法：

*  java.lang.Object

## ObjectMapper示例 ##

选择使用任何编辑器创建以下java程序在 C:/> Jackson\_WORKSPACE

File: JacksonTester.java

import java.io.IOException;
    import org.codehaus.jackson.JsonParseException;
    import org.codehaus.jackson.map.JsonMappingException;
    import org.codehaus.jackson.map.ObjectMapper;
    import org.codehaus.jackson.map.SerializationConfig;
    
    public class JacksonTester {
       
       public static void main(String args[]){
       
          ObjectMapper mapper = new ObjectMapper();
          String jsonString = "{\"name\":\"Mahesh\", \"age\":21}";
    
          //map json to student
          try {
       
             Student student = mapper.readValue(jsonString, Student.class);
             System.out.println(student);
             mapper.enable(SerializationConfig.Feature.INDENT_OUTPUT);
             jsonString = mapper.writeValueAsString(student);
             System.out.println(jsonString);
    
          } 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+ " ]";
       }	
    }

验证结果

使用 javac 编译如下类：

C:\Jackson_WORKSPACE>javac JacksonTester.java

现在运行jacksonTester看到的结果：

C:\Jackson_WORKSPACE>java JacksonTester

验证输出

Student [ name: Mahesh, age: 21 ]
    {
      "name" : "Mahesh",
      "age" : 21
    }