在 JSON 中存储新旧行状态
存储新旧行状态的最佳方式是使用 JSON 列。因此，对于您要启用审核日志记录的每个表，您可以创建一个审核日志表，如下所示：
CREATE TABLE book_audit_log (
book_id BIGINT NOT NULL,
old_row_data JSON,
new_row_data JSON,
dml_type ENUM('INSERT', 'UPDATE', 'DELETE') NOT NULL,
dml_timestamp TIMESTAMP NOT NULL,
dml_created_by VARCHAR(255) NOT NULL,
PRIMARY KEY (book_id, dml_type, dml_timestamp)
)
-
book_id 列存储已创建、更新或删除的 book 行的标识符。
-
old_row_data 是一个 JSON 列，它将在执行 INSERT、UPDATE 或 DELETE 语句之前捕获 book 记录的状态。
-
new_row_data 是一个 JSON 列，将在执行 INSERT、UPDATE 或 DELETE 语句后捕获 book 记录的状态。
-
dml_type 是一个枚举列，用于存储创建、更新或删除给定 book 记录的 DML 语句类型。
-
dml_timestamp 存储 DML 语句执行时间戳。
-
dml_created_by 存储发出 INSERT、UPDATE 或 DELETE DML 语句的应用程序用户。
使用触发器拦截 INSERT、UPDATE 和 DELETE DML 语句
现在，要输入审计日志表，您需要创建以下 3 个触发器：
CREATE TRIGGER book_insert_audit_trigger
AFTER INSERT ON book FOR EACH ROW
BEGIN
INSERT INTO book_audit_log (
book_id,
old_row_data,
new_row_data,
dml_type,
dml_timestamp,
dml_created_by
)
VALUES(
NEW.id,
null,
JSON_OBJECT(
"title", NEW.title,
"author", NEW.author,
"price_in_cents", NEW.price_in_cents,
"publisher", NEW.publisher
),
'INSERT',
CURRENT_TIMESTAMP,
@logged_user
);
END
CREATE TRIGGER book_update_audit_trigger
AFTER UPDATE ON book FOR EACH ROW
BEGIN
INSERT INTO book_audit_log (
book_id,
old_row_data,
new_row_data,
dml_type,
dml_timestamp,
dml_created_by
)
VALUES(
NEW.id,
JSON_OBJECT(
"title", OLD.title,
"author", OLD.author,
"price_in_cents", OLD.price_in_cents,
"publisher", OLD.publisher
),
JSON_OBJECT(
"title", NEW.title,
"author", NEW.author,
"price_in_cents", NEW.price_in_cents,
"publisher", NEW.publisher
),
'UPDATE',
CURRENT_TIMESTAMP,
@logged_user
);
END
CREATE TRIGGER book_delete_audit_trigger
AFTER DELETE ON book FOR EACH ROW
BEGIN
INSERT INTO book_audit_log (
book_id,
old_row_data,
new_row_data,
dml_type,
dml_timestamp,
dml_created_by
)
VALUES(
OLD.id,
JSON_OBJECT(
"title", OLD.title,
"author", OLD.author,
"price_in_cents", OLD.price_in_cents,
"publisher", OLD.publisher
),
null,
'DELETE',
CURRENT_TIMESTAMP,
@logged_user
);
END
JSON_OBJECT MySQL 函数允许我们创建一个 JSON 对象，该对象采用提供的键值对。
dml_type 列的值设置为INSERT、UPDATE 或DELETE，dml_timestamp 的值设置为CURRENT_TIMESTAMP。
dml_created_by 列设置为@logged_user MySQL 会话变量的值，该变量先前由应用程序使用当前登录的用户设置：
Session session = entityManager.unwrap(Session.class);
Dialect dialect = session.getSessionFactory()
.unwrap(SessionFactoryImplementor.class)
.getJdbcServices()
.getDialect();
session.doWork(connection -> {
update(
connection,
String.format(
"SET @logged_user = '%s'",
ReflectionUtils.invokeMethod(
dialect,
"escapeLiteral",
LoggedUser.get()
)
)
);
});
测试时间
在book 表上执行 INSERT 语句时：
INSERT INTO book (
id,
author,
price_in_cents,
publisher,
title
)
VALUES (
1,
'Vlad Mihalcea',
3990,
'Amazon',
'High-Performance Java Persistence 1st edition'
)
我们可以看到book_audit_log中插入了一条记录，该记录捕获了刚刚在book表上执行的INSERT语句：
| book_id | old_row_data | new_row_data | dml_type | dml_timestamp | dml_created_by |
|---------|--------------|--------------------------------------------------------------------------------------------------------------------------------------|----------|---------------------|----------------|
| 1 | | {"title": "High-Performance Java Persistence 1st edition", "author": "Vlad Mihalcea", "publisher": "Amazon", "price_in_cents": 3990} | INSERT | 2020-07-29 13:40:15 | Vlad Mihalcea |
更新book 表行时：
UPDATE book
SET price_in_cents = 4499
WHERE id = 1
我们可以看到book 表上的AFTER UPDATE 触发器将向book_audit_log 添加一条新记录：
| book_id | old_row_data | new_row_data | dml_type | dml_timestamp | dml_created_by |
|---------|--------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------|----------|---------------------|----------------|
| 1 | | {"title": "High-Performance Java Persistence 1st edition", "author": "Vlad Mihalcea", "publisher": "Amazon", "price_in_cents": 3990} | INSERT | 2020-07-29 13:40:15 | Vlad Mihalcea |
| 1 | {"title": "High-Performance Java Persistence 1st edition", "author": "Vlad Mihalcea", "publisher": "Amazon", "price_in_cents": 3990} | {"title": "High-Performance Java Persistence 1st edition", "author": "Vlad Mihalcea", "publisher": "Amazon", "price_in_cents": 4499} | UPDATE | 2020-07-29 13:50:48 | Vlad Mihalcea |
删除book 表行时：
DELETE FROM book
WHERE id = 1
book 表上的 AFTER DELETE 触发器将新记录添加到 book_audit_log：
| book_id | old_row_data | new_row_data | dml_type | dml_timestamp | dml_created_by |
|---------|--------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------|----------|---------------------|----------------|
| 1 | | {"title": "High-Performance Java Persistence 1st edition", "author": "Vlad Mihalcea", "publisher": "Amazon", "price_in_cents": 3990} | INSERT | 2020-07-29 13:40:15 | Vlad Mihalcea |
| 1 | {"title": "High-Performance Java Persistence 1st edition", "author": "Vlad Mihalcea", "publisher": "Amazon", "price_in_cents": 3990} | {"title": "High-Performance Java Persistence 1st edition", "author": "Vlad Mihalcea", "publisher": "Amazon", "price_in_cents": 4499} | UPDATE | 2020-07-29 13:50:48 | Vlad Mihalcea |
| 1 | {"title": "High-Performance Java Persistence 1st edition", "author": "Vlad Mihalcea", "publisher": "Amazon", "price_in_cents": 4499} | | DELETE | 2020-07-29 14:05:33 | Vlad Mihalcea |
就是这样！