Jackson 反序列化原理浅析

Mashiro

2022 年 09 月 14 日

1111 次浏览

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1952字数

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## 引言

在练习使用Axios传post时发现默认使用的是json传参，而servlet提供的getParameter(String s)方法无法解析这种语法，因此了解到Jackson，对其的序列化与反序列化原理很感兴趣，所以浅析一下其原理。

### 代码测试

```json
// 测试json语句
{"username":"LiHua","password":"233"}
```

正确User.class

```java
public class User {

private String username;
    private String password;

private User() {
    }

public String getUsername() {
        return username;
    }

public String getPassword() {
        return password;
    }
}
```

正确解析

```java
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	System.out.println("POST!!!");

// 读取请求内容
    BufferedReader br = new BufferedReader(new InputStreamReader(request.getInputStream(), StandardCharsets.UTF_8));
    String line;
    StringBuilder sb = new StringBuilder();
    while ((line = br.readLine()) != null) {
    	sb.append(line);
	}
    // 解析json
    ObjectMapper objectMapper = new ObjectMapper();
    User user = objectMapper.readValue(sb.toString(), User.class);

System.out.println("username: " + userErr.getUsername());
    System.out.println("password: " + userErr.getPassword());
    }
```

错误UserErr.class

```java
public class UserErr {

private String usernameaaa;
    private String password;

private UserErr() {
    }

public String getUsernameaaa() {
        return usernameaaa;
    }

public String getPassword() {
        return password;
    }
}
```

错误解析

```java
UserErr user = objectMapper.readValue(sb.toString(), UserErr.class);

System.out.println("username: " + user.getUsernameaaa());
    System.out.println("password: " + user.getPassword());
```

分别输出：
成功：
![成功](https://cdn2.feczine.cn/2022/09/14/63218596c038b.jpg)
失败：
![失败](https://cdn2.feczine.cn/2022/09/14/6321859734ef9.jpg)

### 结论猜测：