springboot~mybatis-plus更优雅的处理mysql8.0的json字段
MySQL 8.0 引入了许多新特性和改进，旨在增强性能、可用性和安全性。以下是一些主要的新特性：数据字典，窗口函数，公共表表达式 (CTE)，JSON 改进，隐式列和生成列，字符集和排序规则，原生支持 GIS 功能，支持更强的 SSL/TLS 加密选项等。下面文章主要介绍mysql字段为Json类型自动映射到java的实体类型的方法：
数据表结构
CREATE TABLE user_actions (
action_id INT PRIMARY KEY,
user_id INT,
action_time DATETIME,
action_details JSON
);
-- 示例数据插入
INSERT INTO user_actions (action_id, user_id, action_time, action_details) VALUES
(1, 1, '2025-04-01 10:00:00', '{"action": "login", "duration": 120}'),
(2, 1, '2025-04-02 11:00:00', '{"action": "view", "item_id": 101, "duration": 300}'),
(3, 2, '2025-04-05 12:00:00', '{"action": "login", "duration": 150}'),
(4, 3, '2025-04-08 13:00:00', '{"action": "purchase", "item_id": 102, "amount": 29.99}'),
(5, 2, '2025-04-09 14:00:00', '{"action": "view", "item_id": 103, "duration": 200}'),
(6, 3, '2025-04-09 15:00:00', '{"action": "view", "item_id": 101, "duration": 100}');实体结构
@Data
@TableName(value = "user_actions", autoResultMap = true)
public class UserAction {
private Integer actionId;
private Integer userId;
private LocalDateTime actionTime;
@TableField(typeHandler = JsonTypeHandler.class)
private ActionDetail actionDetails;
}
@Data
class ActionDetail {
private String action;
private Integer duration;
@JsonProperty("item_id")
private Integer itemId;
private double amount;
}注意：实体类需要添加@TableName(autoResultMap = true)
字段上添加对应的注解@TableField(typeHandler = JsonTypeHandler.class)
类型转换器JsonTypeHandler代码
@MappedTypes(Map.class)
public class JsonTypeHandler<T> extends BaseTypeHandler<T> {
private static final ObjectMapper objectMapper = new ObjectMapper();
private Class<T> type;
public JsonTypeHandler(Class<T> type) {
this.type = type;
}
@Override
public void setNonNullParameter(PreparedStatement ps, int i, T parameter, JdbcType jdbcType) throws SQLException {
try {
ps.setString(i, objectMapper.writeValueAsString(parameter));
}
catch (IOException e) {
throw new SQLException("Failed to convert JSON to String", e);
}
}
@Override
public T getNullableResult(ResultSet rs, String columnName) throws SQLException {
String json = rs.getString(columnName);
if (json != null) {
try {
return objectMapper.readValue(json, type);
}
catch (IOException e) {
throw new SQLException("Failed to convert String to JSON", e);
}
}
return null;
}
@Override
public T getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
String json = rs.getString(columnIndex);
if (json != null) {
try {
return objectMapper.readValue(json, type);
}
catch (IOException e) {
throw new SQLException("Failed to convert String to JSON", e);
}
}
return null;
}
@Override
public T getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
String json = cs.getString(columnIndex);
if (json != null) {
try {
return objectMapper.readValue(json, type);
}
catch (IOException e) {
throw new SQLException("Failed to convert String to JSON", e);
}
}
return null;
}
}最后，可正常解析出结果
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