24khandsome's Blog

24khandsome's Blog

Mybati执行对象创建过程与执行

发表于 更新于 分类于
sqlSession与Statement的创建过程与SQL语句的执行流程

概要：

  1. 执行流程解析
  2. myBatis插件开发

执行流程分析

Configuration全局配置对象创建

讲解解析流程之前先回顾一下myBatis 中配置文件的结构：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
mybatis-config.xml
<configuration>
  <properties/>
  <settting/>
  <typeHandlers/>
  <..../>
  <mappers/>
</configuration>
mybatis-mapper.xml
<mapper > 
  <cache/>
  <resultMap/>
  <select/>  
  <update/> 
  <delete/> 
  <insert/> 
</mapper>

配置文件的解析流程即是将上述XML描述元素转换成对应的JAVA对像过程，其最终转换对像及其关系如下图：

配置元素解析构建器

1
2
3
4
5
6
7
8
9
10
11
12
13
>org.apache.ibatis.builder.xml.XMLConfigBuilder
    //生成org.apache.ibatis.session.Configuration对象 生命周期：整个应用周期
 >org.apache.ibatis.builder.xml.XMLMapperBuilder
    //生成生成configuration对象的MappedStatement key为namcspace + 语语句块的id	 
    //生命周期：整个应用周期
  >org.apache.ibatis.builder.xml.XMLStatementBuilder
    //Statement 生命周期：整个应用周期
   >org.apache.ibatis.builder.SqlSourceBuilder
    //增删改查语句内容构建
    >org.apache.ibatis.scripting.xmltags.XMLScriptBuilder
    //动态SQL构建
 >org.apache.ibatis.builder.annotation.MapperAnnotationBuilder
    //用注解方式构建起如@Select（...）

SqlSession 会话对象创建

首先我们还是先来了解一下会话对像的组成结构如下图：

image-20210516131743828

会话构建源码解析:

1
2
3
4
5
6
>org.apache.ibatis.session.defaults.DefaultSqlSessionFactory#openSession(boolean)
>org.apache.ibatis.session.defaults.DefaultSqlSessionFactory#openSessionFromDataSource
>org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory#newTransaction()
>org.apache.ibatis.session.Configuration#newExecutor() >org.apache.ibatis.executor.SimpleExecutor#SimpleExecutor >org.apache.ibatis.executor.CachingExecutor#CachingExecutor 
//执行器插件包装 
>org.apache.ibatis.plugin.InterceptorChain#pluginAll(executor) >org.apache.ibatis.session.defaults.DefaultSqlSession#DefaultSqlSession()

方法执行流程

image-20210516135633903

StatementHandler 源码解析

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
>org.apache.ibatis.session.defaults.DefaultSqlSession#selectList()
 >org.apache.ibatis.executor.CachingExecutor#query()
  >org.apache.ibatis.executor.BaseExecutor#query()
   >org.apache.ibatis.executor.BaseExecutor#queryFromDatabase
>org.apache.ibatis.session.Configuration#newStatementHandler
org.apache.ibatis.executor.statement.BaseStatementHandler#BaseStatementHandler
org.apache.ibatis.session.Configuration#newParameterHandler
org.apache.ibatis.plugin.InterceptorChain#pluginAll(parameterHandler)
org.apache.ibatis.session.Configuration#newResultSetHandler
org.apache.ibatis.plugin.InterceptorChain#pluginAll(resultSetHandler)
>org.apache.ibatis.plugin.InterceptorChain#pluginAll(statementHandler)
>org.apache.ibatis.executor.BaseExecutor#getConnection
>org.apache.ibatis.executor.statement.PreparedStatementHandler#instantiateStatement
>org.apache.ibatis.executor.statement.PreparedStatementHandler#parameterize
>org.apache.ibatis.scripting.defaults.DefaultParameterHandler#setParameters
org.apache.ibatis.type.BaseTypeHandler#setParameter
org.apache.ibatis.type.UnknownTypeHandler#setNonNullParameter
org.apache.ibatis.type.IntegerTypeHandler#setNonNullParameter

Mapper接口对象创建

1
2
3
4
5
6
org.apache.ibatis.binding.MapperProxyFactory.newInstance(MapperProxyFactory.java:48)
org.apache.ibatis.binding.MapperProxyFactory.newInstance(MapperProxyFactory.java:53)
org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:50)
org.apache.ibatis.session.Configuration.getMapper(Configuration.java:779)
org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:291)
com.study.SecondLevelCacheTest.test01(SecondLevelCacheTest.java:46)

MyBatis插件开发

插件的四大扩展点

1、Executor

2、StatementHandler

3、ParameterHandler

4、ResultSetHandler

Executor提供了增删改查的接口.

StatementHandler负责处理Mybatis与JDBC之间Statement的交互.

ResultSetHandler负责处理Statement执行后产生的结果集，生成结果列表.

ParameterHandler是Mybatis实现Sql入参设置的对象。

分页插件实现

用户在接口中声明Page 对像实现后，由插件实现自动分页。

使用示例如下： 

1
2
3
4
5
public class Page implements java.io.Serializable {   
    private int szie; // 每页大    
    private int number; // 当前页码
}
 List<User>  selectUserList(@Param("user") User user, @Param("page") PageDTO page);
1
2
3
<select id="selectUserList" resultType="com.study.pojo.User">
    select * from user where id = #{user.id}
</select>

实现目标分解：

1、判断方法参数是否包含Page对象

2、取出page对象生成 limit 语句

3、修改SQL语句添加 limit 语句

4、上述操作必须在Statement（PrepareStatement）对象生成之前完成

image-20210516160916272

image-20210516161122668

根据第四点和上面俩图得知插件拦截的时，拦截的目标类和目标方法如下

1
2
3
4
public interface StatementHandler {
    Statement prepare(Connection connection, Integer transactionTimeout)
      throws SQLException;
}

所以最终的拦截器代码如下

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
public class PagePlugin implements Interceptor {
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
       return invocation.getTarget();
    }

    @Override
    public Object plugin(Object target) {
        if(target instanceof StatementHandler){
            return Proxy.newProxyInstance(this.getClass().getClassLoader(),
                    new Class[]{StatementHandler.class},
                    new PageHandler((StatementHandler) target));
        }
        return target;
    }

    @Override
    public void setProperties(Properties properties) {

    }

    private class PageHandler implements  InvocationHandler{

        private StatementHandler statementHandler;

        public PageHandler(StatementHandler statementHandler) {
            this.statementHandler = statementHandler;
        }

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if(method.getName().equals("prepare")){
                ((Map)statementHandler.getBoundSql().getParameterObject()).values().stream()
                        .filter(e -> e instanceof PageDTO)
                        .findFirst()
                        .ifPresent(
                                page -> {

                                    appendPageSql((PageDTO) page);
                                }
                        );
            }
            return method.invoke(statementHandler,args);
        }

        private void appendPageSql(PageDTO page) {
            BoundSql boundSql = statementHandler.getBoundSql();
            String sql = boundSql.getSql();
            String appendString = String.format(" limit %s,%s",(page.getNumber()-1) * page.getSzie(),page.getSzie());
            String result = sql + appendString;
            try {
                setField(boundSql,"sql",result);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        private void setField(BoundSql boundSql, String field, String result) throws IllegalAccessException, NoSuchFieldException {
            Field declaredField = BoundSql.class.getDeclaredField(field);
            declaredField.setAccessible(true);
            declaredField.set(boundSql,result);
        }
    }

SQL性能插件

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
@Intercepts({@Signature(type = StatementHandler.class, method = "query", args = {Statement.class, ResultHandler.class}),
        @Signature(type = StatementHandler.class, method = "update", args = {Statement.class}),
        @Signature(type = StatementHandler.class, method = "batch", args = {Statement.class})})
public class PerformanceInterceptor implements Interceptor {
    private static final String JDBC4_PREPARED_STATEMENT = "com.mysql.jdbc.JDBC4PreparedStatement";

    /**
     * SQL 执行最大时长，超过自动停止运行，有助于发现问题。
     */
    @Getter
    @Setter
    private long maxTime = 0;
    /**
     * SQL 是否格式化
     */
    @Getter
    @Setter
    private boolean format = false;


    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        Statement statement;
        Object firstArg = invocation.getArgs()[0];
        if (Proxy.isProxyClass(firstArg.getClass())) {
            statement = (Statement) SystemMetaObject.forObject(firstArg).getValue("h.statement");
        } else {
            statement = (Statement) firstArg;
        }
        try {
            statement = (Statement) SystemMetaObject.forObject(statement).getValue("stmt.statement");
        } catch (Exception e) {
            // do nothing
        }

        String originalSql = null;
        String stmtClassName = statement.getClass().getName();
        if (JDBC4_PREPARED_STATEMENT.equals(stmtClassName)) {
            try {
                Class<?> clazz = Class.forName(JDBC4_PREPARED_STATEMENT);
                Method druidGetSqlMethod = clazz.getMethod("getSql");
                Object stmtSql = druidGetSqlMethod.invoke(statement);
                if (stmtSql != null && stmtSql instanceof String) {
                    originalSql = (String) stmtSql;
                }
            } catch (Exception ignored) {
            }
        }

        if (originalSql == null) {
            originalSql = statement.toString();
        }
        originalSql = originalSql.replaceAll("[\\s]+", " ");
        int index = originalSql.indexOf(':');
        if (index > 0) {
            originalSql = originalSql.substring(index + 1, originalSql.length());
        }
        String sqlFormat = SqlUtil.sqlFormat(originalSql, format);
        Object target = realTarget(invocation.getTarget());
        MetaObject metaObject = SystemMetaObject.forObject(target);
        MappedStatement ms = (MappedStatement) metaObject.getValue("delegate.mappedStatement");
        Logger mybatisLogger = LoggerFactory.getLogger(this.getClass());
        // 计算执行 SQL 耗时
        long start = System.currentTimeMillis();
        Object result = null;
        try {
            result = invocation.proceed();
        } catch (InvocationTargetException | IllegalAccessException e) {
            long timing =  System.currentTimeMillis() - start;
            StringBuilder formatSql = new StringBuilder()
                    .append("execute sql error, use time：").append(timing).append("\n")
                    .append(sqlFormat);
            mybatisLogger.error(formatSql.toString());
            throw e;
        }
        long timing = System.currentTimeMillis() - start;

        // 格式化 SQL 打印执行结果
        StringBuilder formatSql = new StringBuilder().append("Execute sql use time：").append(timing)
                .append("\n")
                .append(" Execute SQL：").append(sqlFormat)
                .append("\n")
                .append(" result: ").append(result);

        if (this.getMaxTime() >= 1 && timing > this.getMaxTime()) {
            mybatisLogger.error(formatSql.toString());
        } else {
            mybatisLogger.debug(formatSql.toString());
        }

        return result;
    }

    @Override
    public Object plugin(Object target) {
        if (target instanceof StatementHandler) {
            return Plugin.wrap(target, this);
        }
        return target;
    }

    @Override
    public void setProperties(Properties prop) {
        String maxTime = prop.getProperty("maxTime");
        String format = prop.getProperty("format");
        if (!StringUtils.isEmptyOrWhitespaceOnly(maxTime)) {
            this.maxTime = Long.parseLong(maxTime);
        }
        if (!StringUtils.isEmptyOrWhitespaceOnly(format)) {
            this.format = Boolean.valueOf(format);
        }
    }

    public static <T> T realTarget(Object target) {
        if (Proxy.isProxyClass(target.getClass())) {
            MetaObject metaObject = SystemMetaObject.forObject(target);
            return realTarget(metaObject.getValue("h.target"));
        }
        return (T) target;
    }

}

带参数SQL打印插件

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
@Intercepts
        ({
                @Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}),
                @Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class})
        })
public class SqlPrintInterceptor implements Interceptor{

    private static final Logger log = LoggerFactory.getLogger(SqlPrintInterceptor.class);

    private static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        MappedStatement mappedStatement = (MappedStatement) invocation.getArgs()[0];
        Object parameterObject = null;
        if (invocation.getArgs().length > 1) {
            parameterObject = invocation.getArgs()[1];
        }

        long start = System.currentTimeMillis();

        Object result = invocation.proceed();

        String statementId = mappedStatement.getId();
        BoundSql boundSql = mappedStatement.getBoundSql(parameterObject);
        Configuration configuration = mappedStatement.getConfiguration();
        String sql = getSql(boundSql, parameterObject, configuration);

        long end = System.currentTimeMillis();
        long timing = end - start;
        if(log.isInfoEnabled()){
            log.info("执行sql耗时:" + timing + " ms" + " - id:" + statementId + " - Sql:" );
            log.info("   "+sql);
        }

        return result;
    }

    @Override
    public Object plugin(Object target) {
        if (target instanceof Executor) {
            return Plugin.wrap(target, this);
        }
        return target;
    }

    @Override
    public void setProperties(Properties properties) {
    }

    private String getSql(BoundSql boundSql, Object parameterObject, Configuration configuration) {
        String sql = boundSql.getSql().replaceAll("[\\s]+", " ");
        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
        TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();
        if (parameterMappings != null) {
            for (int i = 0; i < parameterMappings.size(); i++) {
                ParameterMapping parameterMapping = parameterMappings.get(i);
                if (parameterMapping.getMode() != ParameterMode.OUT) {
                    Object value;
                    String propertyName = parameterMapping.getProperty();
                    if (boundSql.hasAdditionalParameter(propertyName)) {
                        value = boundSql.getAdditionalParameter(propertyName);
                    } else if (parameterObject == null) {
                        value = null;
                    } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
                        value = parameterObject;
                    } else {
                        MetaObject metaObject = configuration.newMetaObject(parameterObject);
                        value = metaObject.getValue(propertyName);
                    }
                    sql = replacePlaceholder(sql, value);
                }
            }
        }
        return sql;
    }

    private String replacePlaceholder(String sql, Object propertyValue) {
        String result;
        if (propertyValue != null) {
            if (propertyValue instanceof String) {
                result = "'" + propertyValue + "'";
            } else if (propertyValue instanceof Date) {
                result = "'" + DATE_FORMAT.format(propertyValue) + "'";
            } else {
                result = propertyValue.toString();
            }
        } else {
            result = "null";
        }
        return sql.replaceFirst("\\?", Matcher.quoteReplacement(result));
    }
}