{"id":10020576,"date":"2024-12-31T11:36:20","date_gmt":"2024-12-31T03:36:20","guid":{"rendered":"https:\/\/itmax.cn\/?p=10020576"},"modified":"2024-12-31T11:36:20","modified_gmt":"2024-12-31T03:36:20","slug":"%e7%94%b1-mybatis-%e6%ba%90%e7%a0%81%e7%95%85%e8%b0%88%e8%bd%af%e4%bb%b6%e8%ae%be%e8%ae%a1%ef%bc%88%e4%b8%83%ef%bc%89%ef%bc%9a%e4%bb%8e%e6%a0%b9%e4%b8%8a%e7%90%86%e8%a7%a3-mybatis-%e4%b8%80%e7%ba%a7","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10020576","title":{"rendered":"\u7531 Mybatis \u6e90\u7801\u7545\u8c08\u8f6f\u4ef6\u8bbe\u8ba1\uff08\u4e03\uff09\uff1a\u4ece\u6839\u4e0a\u7406\u89e3 Mybatis \u4e00\u7ea7\u7f13\u5b58"},"content":{"rendered":"

\u4f5c\u8005\uff1a\u4eac\u4e1c\u4fdd\u9669 \u738b\u5955\u9f99<\/p>\n

\u672c\u7bc7\u6211\u4eec\u6765\u8bb2 \u4e00\u7ea7\u7f13\u5b58<\/strong>\uff0c\u91cd\u70b9\u5173\u6ce8\u5b83\u7684\u5b9e\u73b0\u539f\u7406\uff1a\u4f55\u65f6\u751f\u6548\u3001\u751f\u6548\u8303\u56f4\u548c\u4f55\u65f6\u5931\u6548\uff0c\u5728\u672a\u6765\u8bbe\u8ba1\u7f13\u5b58\u4f7f\u7528\u65f6\uff0c\u63d0\u4f9b\u4e00\u4e9b\u501f\u9274\u548c\u53c2\u8003\u3002<\/p>\n

1. \u51c6\u5907\u5de5\u4f5c<\/h3>\n

\u5b9a\u4e49\u5b9e\u4f53<\/h4>\n
public class Department {\n\n    public Department(String id) {\n        this.id = id;\n    }\n\n    private String id;\n\n    \/**\n     * \u90e8\u95e8\u540d\u79f0\n     *\/\n    private String name;\n\n    \/**\n     * \u90e8\u95e8\u7535\u8bdd\n     *\/\n    private String tel;\n\n    \/**\n     * \u90e8\u95e8\u6210\u5458\n     *\/\n    private Set<User> users;\n}\n<\/code><\/pre>\n
<!—-><\/p>\n
public class User {\n\n    private String id;\n\n    private String name;\n\n    private Integer age;\n\n    private LocalDateTime birthday;\n\n    private Department department;\n}\n<\/code><\/pre>\n
\u5b9a\u4e49 Mapper.xml<\/h4>\n
DepartmentMapper.xml\uff0c\u4e24\u6761 SQL\uff1a\u4e00\u6761\u6839\u636e ID \u67e5\u8be2\uff1b\u4e00\u6761\u6e05\u9664\u7f13\u5b58\uff0c\u6807\u8bb0\u4e86 fulshCache<\/strong> \u6807\u7b7e\uff0c\u5c06\u5176\u8bbe\u7f6e\u4e3a true \u540e\uff0c\u53ea\u8981\u8bed\u53e5\u88ab\u8c03\u7528\uff0c\u90fd\u4f1a\u5c06\u672c\u5730\u7f13\u5b58\u548c\u4e8c\u7ea7\u7f13\u5b58\u6e05\u7a7a\uff08\u9ed8\u8ba4\u503c\u4e3a false\uff09<\/p>\n
<select id="findById" resultType="Department">\n    select * from department\n    where id = #{id}\n<\/select>\n\n<select id="cleanCathe" resultType="int" flushCache="true">\n    select count(department.id) from department;\n<\/select>\n<\/code><\/pre>\n
UserMapper.xml\uff0c\u8054\u8868\u67e5\u8be2\u7528\u6237\u4fe1\u606f\uff1a<\/p>\n
<select id="findAll" resultMap="userMap">\n    select u.*, td.id, td.name as department_name\n    from user u\n    left join department td\n    on u.department_id = td.id\n<\/select>\n<\/code><\/pre>\n
2. \u4e00\u7ea7\u7f13\u5b58<\/h3>\n
\u4e00\u7ea7\u7f13\u5b58\u7684\u751f\u6548\u8303\u56f4 SqlSession<\/code> \u7ea7\u522b\u7684\uff0c\u4e0d\u540c SqlSession<\/code> \u95f4\u4e0d\u5171\u4eab\u7f13\u5b58\uff0c\u5b83\u9ed8\u8ba4\u60c5\u51b5\u4e0b\u662f\u542f\u7528\u7684\u3002\u4e3b\u8981\u4f5c\u7528\u662f\u51cf\u5c11\u5728\u540c\u4e00\u4e2a\u67e5\u8be2 SQL \u4f1a\u8bdd\u4e2d\u5bf9\u6570\u636e\u5e93\u7684\u91cd\u590d\u67e5\u8be2\uff0c\u4ece\u800c\u63d0\u9ad8\u6027\u80fd\u3002\u4ee5\u5982\u4e0b\u7528\u4f8b\u4e3a\u4f8b\uff1a<\/p>\n
    public static void main(String[] args) throws IOException {\n        InputStream xml = Resources.getResourceAsStream("mybatis-config.xml");\n        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();\n        \/\/ \u5f00\u542f\u4e8c\u7ea7\u7f13\u5b58\u9700\u8981\u5728\u540c\u4e00\u4e2aSqlSessionFactory\u4e0b\uff0c\u4e8c\u7ea7\u7f13\u5b58\u5b58\u5728\u4e8e SqlSessionFactory \u751f\u547d\u5468\u671f\uff0c\u5982\u6b64\u624d\u80fd\u547d\u4e2d\u4e8c\u7ea7\u7f13\u5b58\n        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(xml);\n\n        SqlSession sqlSession = sqlSessionFactory.openSession();\n        DepartmentMapper departmentMapper = sqlSession.getMapper(DepartmentMapper.class);\n        System.out.println("----------department\u7b2c\u4e00\u6b21\u67e5\u8be2 \u2193------------");\n        departmentMapper.findById("18ec781fbefd727923b0d35740b177ab");\n        System.out.println("----------department\u4e00\u7ea7\u7f13\u5b58\u751f\u6548\uff0c\u63a7\u5236\u53f0\u770b\u4e0d\u89c1SQL \u2193------------");\n        departmentMapper.findById("18ec781fbefd727923b0d35740b177ab");\n\n    }\n<\/code><\/pre>\n
\u53ef\u4ee5\u53d1\u73b0\u5728\u7b2c\u4e8c\u6b21\u67e5\u8be2\u65f6\uff0c\u4e00\u7ea7\u7f13\u5b58\u751f\u6548\uff0c\u63a7\u5236\u53f0\u6ca1\u6709\u51fa\u73b0SQL\uff1a<\/p>\n
\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\"<\/p>\n
\u800c\u6211\u4eec\u6e05\u7a7a\u4e0b\u4e00\u7ea7\u7f13\u5b58\u518d\u8bd5\u8bd5\uff1a<\/p>\n
    public static void main(String[] args) throws IOException {\n        InputStream xml = Resources.getResourceAsStream("mybatis-config.xml");\n        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();\n        \/\/ \u5f00\u542f\u4e8c\u7ea7\u7f13\u5b58\u9700\u8981\u5728\u540c\u4e00\u4e2aSqlSessionFactory\u4e0b\uff0c\u4e8c\u7ea7\u7f13\u5b58\u5b58\u5728\u4e8e SqlSessionFactory \u751f\u547d\u5468\u671f\uff0c\u5982\u6b64\u624d\u80fd\u547d\u4e2d\u4e8c\u7ea7\u7f13\u5b58\n        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(xml);\n\n        SqlSession sqlSession = sqlSessionFactory.openSession();\n        DepartmentMapper departmentMapper = sqlSession.getMapper(DepartmentMapper.class);\n        System.out.println("----------department\u7b2c\u4e00\u6b21\u67e5\u8be2 \u2193------------");\n        departmentMapper.findById("18ec781fbefd727923b0d35740b177ab");\n        System.out.println("----------department\u4e00\u7ea7\u7f13\u5b58\u751f\u6548\uff0c\u63a7\u5236\u53f0\u770b\u4e0d\u89c1SQL \u2193------------");\n        departmentMapper.findById("18ec781fbefd727923b0d35740b177ab");\n        System.out.println("----------\u6e05\u9664\u4e00\u7ea7\u7f13\u5b58 \u2193------------");\n        departmentMapper.cleanCathe();\n        System.out.println("----------\u6e05\u9664\u540edepartment\u518d\u4e00\u6b21\u67e5\u8be2\uff0cSQL\u518d\u6b21\u51fa\u73b0 \u2193------------");\n        departmentMapper.findById("18ec781fbefd727923b0d35740b177ab");\n    }\n<\/code><\/pre>\n
\u63a7\u5236\u53f0\u65e5\u5fd7\u5f88\u6e05\u6670\uff0c\u6e05\u9664\u7f13\u5b58\u540e\u53c8\u91cd\u65b0\u67e5\u4e86\u4e00\u904d\uff1a<\/p>\n
\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\"<\/p>\n
\u63a5\u4e0b\u6765\u6211\u4eec\u770b\u4e00\u4e0b\u4e0d\u540c SqlSession<\/code> \u95f4\u4e00\u7ea7\u7f13\u5b58\u662f\u5426\u5171\u4eab\uff0c\u521b\u5efa\u4e00\u4e2a\u65b0\u7684 SqlSession sqlSession1<\/code> \u6267\u884c\u76f8\u540c\u7684SQL\uff1a<\/p>\n
    public static void main(String[] args) throws IOException {\n        SqlSession sqlSession = sqlSessionFactory.openSession();\n        SqlSession sqlSession1 = sqlSessionFactory.openSession();\n        DepartmentMapper departmentMapper = sqlSession.getMapper(DepartmentMapper.class);\n        DepartmentMapper departmentMapper1 = sqlSession1.getMapper(DepartmentMapper.class);\n        System.out.println("----------department\u7b2c\u4e00\u6b21\u67e5\u8be2 \u2193------------");\n        departmentMapper.findById("18ec781fbefd727923b0d35740b177ab");\n        System.out.println("----------sqlSession1\u4e0bdepartment\u6267\u884c\u76f8\u540c\u7684SQL\uff0c\u63a7\u5236\u53f0\u51fa\u73b0SQL \u2193------------");\n        departmentMapper1.findById("18ec781fbefd727923b0d35740b177ab");\n    }\n<\/code><\/pre>\n
\u5982\u63a7\u5236\u53f0\u65e5\u5fd7\u6240\u793a\uff0c\u53ef\u4ee5\u53d1\u73b0\u5728\u4e0d\u540c\u7684 SqlSession<\/code> \u4e0b\u4e0d\u5171\u4eab\u4e00\u7ea7\u7f13\u5b58\uff1a<\/p>\n
\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\"<\/p>\n
3. \u4e00\u7ea7\u7f13\u5b58\u539f\u7406<\/h3>\n
\u4e00\u7ea7\u7f13\u5b58\u5728\u67e5\u8be2\u65b9\u6cd5 org.apache.ibatis.executor.BaseExecutor#query<\/code> \u4e2d\u751f\u6548\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n
public abstract class BaseExecutor implements Executor {\n    \/\/ ...\n    \n    \/\/ \u4e00\u7ea7\u7f13\u5b58\n    protected PerpetualCache localCache;\n\n    public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler,\n                             CacheKey key, BoundSql boundSql) throws SQLException {\n        ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());\n        if (closed) {\n            throw new ExecutorException("Executor was closed.");\n        }\n        \/\/ \u5224\u65ad\u662f\u5426\u5237\u65b0\u672c\u5730\u7f13\u5b58\n        if (queryStack == 0 && ms.isFlushCacheRequired()) {\n            clearLocalCache();\n        }\n        List<E> list;\n        try {\n            queryStack++;\n            \/\/ \u5224\u65ad\u4e00\u7ea7\u7f13\u5b58\u662f\u5426\u5b58\u5728\uff0c\u5b58\u5728\u5219\u76f4\u63a5\u4f5c\u4e3a\u7ed3\u679c\u8fd4\u56de\uff0c\u5426\u5219\u67e5\u8be2\u6570\u636e\u5e93\n            list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;\n            if (list != null) {\n                \/\/ \u5b58\u50a8\u8fc7\u7a0b\u76f8\u5173\u903b\u8f91\n                handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);\n            } else {\n                \/\/ \u672a\u547d\u4e2d\u4e00\u7ea7\u7f13\u5b58\uff0c\u67e5\u8be2\u6570\u636e\u5e93\n                list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);\n            }\n        } finally {\n            queryStack--;\n        }\n        if (queryStack == 0) {\n            for (DeferredLoad deferredLoad : deferredLoads) {\n                deferredLoad.load();\n            }\n            \/\/ issue #601\n            deferredLoads.clear();\n            if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {\n                \/\/ issue #482\n                clearLocalCache();\n            }\n        }\n        return list;\n    }\n\n    private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds,\n                                          ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {\n        List<E> list;\n        \/\/ \u4e00\u7ea7\u7f13\u5b58\u5360\u4f4d\n        localCache.putObject(key, EXECUTION_PLACEHOLDER);\n        try {\n            list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);\n        } finally {\n            \/\/ \u67e5\u8be2\u5b8c\u6210\u540e\u6e05\u9664\u4e00\u7ea7\u7f13\u5b58\n            localCache.removeObject(key);\n        }\n        \/\/ \u6dfb\u52a0\u5230\u4e00\u7ea7\u7f13\u5b58\u4e2d\n        localCache.putObject(key, list);\n        \/\/ \u5b58\u50a8\u8fc7\u7a0b\u76f8\u5173\u903b\u8f91\n        if (ms.getStatementType() == StatementType.CALLABLE) {\n            localOutputParameterCache.putObject(key, parameter);\n        }\n        return list;\n    }\n}\n<\/code><\/pre>\n
\u5176\u4e2d PerpetualCache localCache<\/code> \u4fbf\u662f\u4e00\u7ea7\u7f13\u5b58\uff0c\u5b83\u7684\u5b9e\u73b0\u501f\u52a9\u4e86 HashMap<\/code>\uff1a<\/p>\n
public class PerpetualCache implements Cache {\n\n    private final String id;\n\n    private final Map<Object, Object> cache = new HashMap<>();\n \n    \/\/ ...\n}\n<\/code><\/pre>\n
\u4e00\u7ea7\u7f13\u5b58\u751f\u6548\u7684\u903b\u8f91\u4e5f\u975e\u5e38\u7b80\u5355\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n
\"\u5728\u8fd9\u91cc\u63d2\u5165\u56fe\u7247\u63cf\u8ff0\"<\/p>\n
queryFromDatabase<\/code> \u65b9\u6cd5\u4e2d\u6709\u4e00\u6bb5\u86ee\u6709\u610f\u601d\u7684\u903b\u8f91 localCache.putObject(key, EXECUTION_PLACEHOLDER);<\/code>\uff1a\u5728\u6dfb\u52a0\u4e00\u7ea7\u7f13\u5b58\u524d\u4f1a\u5148\u6dfb\u52a0\u7f13\u5b58 \u5360\u4f4d\u7b26 EXECUTION\/_PLACEHOLDER<\/strong>\uff0c\u4f46\u662f\u8fd9\u4e2a\u5360\u4f4d\u7b26\u5e76\u6ca1\u6709\u88ab\u7528\u4f5c\u4e00\u4e2a\u660e\u786e\u7684\u540c\u6b65\u673a\u5236\u6765\u963b\u6b62\u5176\u4ed6\u7ebf\u7a0b\u7684\u67e5\u8be2\u6267\u884c\uff0c\u6240\u4ee5\u5b83\u53ea\u662f\u6807\u8bb0\u4e00\u4e2a\u67e5\u8be2\u6b63\u5728\u8fdb\u884c\uff0c\u63d0\u4f9b\u4e86<\/strong> \u9632\u6b62\u5728\u540c\u4e00\u4e8b\u52a1\u4e0a\u4e0b\u6587\u4e2d\u91cd\u590d\u6267\u884c\u76f8\u540c\u7684\u67e5\u8be2\u7684 \u57fa\u7840<\/strong>\uff0c\u8fd9\u79cd\u8bbe\u8ba1\u53ef\u80fd\u662f MyBatis \u5f00\u53d1\u8005\u8ba4\u4e3a\u5728\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u6570\u636e\u5e93\u67e5\u8be2\u7684\u5f00\u9500\u76f8\u5bf9\u8f83\u5c0f\u6216\u540c\u4e00\u4e8b\u52a1\u4e2d\u51e0\u4e4e\u4e0d\u6267\u884c\u591a\u6b21\u76f8\u540c\u7684\u67e5\u8be2\uff0c\u800c\u4e0d\u662f\u4e3a\u4e86\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\u4fdd\u8bc1\u4e0d\u51fb\u7a7f\u6570\u636e\u5e93\uff0c\u964d\u4f4e\u6570\u636e\u5e93\u7684\u538b\u529b\u3002<\/p>\n
\u8fd9\u79cd\u8bbe\u8ba1\u6a21\u5f0f\u5728\u5206\u5e03\u5f0f\u7f13\u5b58\u7cfb\u7edf\u4e2d\u5f88\u5e38\u89c1\uff0c\u4e00\u822c\u7528\u4e8e \u89e3\u51b3 \u201d\u7f13\u5b58\u51fb\u7a7f\u201c \u95ee\u9898<\/strong>\uff0c\u5e2e\u52a9\u7cfb\u7edf\u5728\u9ad8\u5e76\u53d1\u73af\u5883\u4e0b\u4fdd\u6301\u7a33\u5b9a\u6027\u3002<\/p>\n
\u4e00\u7ea7\u7f13\u5b58\u5931\u6548\u573a\u666f<\/h4>\n