Mybatis 源码分析--crud

增加源码分析-insert()

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public int insert(String statement, Object parameter) {         //statement就是传进来的要调用xml定义的哪个sql语句，parameter就是调用语句需要传进来的参数对象
return update(statement, parameter);
}

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进入到update方法中

public int update(String statement, Object parameter) {
try {
dirty = true;　　　　　　　　　　　　　　　　　　　　　　　　　//
MappedStatement ms = configuration.getMappedStatement(statement);　　　　//configuration通过传进来的参数，获取对应的映射statement
return executor.update(ms, wrapCollection(parameter));　　　　　　　　　　　　//executor是个代理对象
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error updating database. Cause: " + e, e);
} finally {
ErrorContext.instance().reset();
}
}

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进入到invoke方法中

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {       //参数中的method是Executor.update
try {

//获取声明的方法集[Executor.query],这个集合是自己在mybatis配置文件plugin节点下定义的要拦截的方法集
Set<Method> methods = signatureMap.get(method.getDeclaringClass());　
if (methods != null && methods.contains(method)) {　　　　　　　　　　　　　　// methods.contains(method)==false
return interceptor.intercept(new Invocation(target, method, args));
}

//target是CachingExecutor类型的，其中有两个参数SimpleExecutor的delegate和TransactionalCacheManager类型的tcm

//args是Object数组，[0]=MappedStatement,[1]=Employee(上面update方法传进来的参数)
return method.invoke(target, args);　　　　　　　　//交给target所指定的方法继续执行程序　　　　　　　　　　　
} catch (Exception e) {
throw ExceptionUtil.unwrapThrowable(e);
}
}

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public int update(MappedStatement ms, Object parameterObject) throws SQLException {
flushCacheIfRequired(ms);　　　　　　　　　　　　　　　　　　　　　　　　　　　　//如果有缓存，则清除。
return delegate.update(ms, parameterObject);
}

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public int update(MappedStatement ms, Object parameter) throws SQLException {
ErrorContext.instance().resource(ms.getResource()).activity("executing an update").object(ms.getId());
if (closed) throw new ExecutorException("Executor was closed.");
clearLocalCache();　　　　　　　　　　　　　　//清除本地缓存
return doUpdate(ms, parameter);
}

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public int doUpdate(MappedStatement ms, Object parameter) throws SQLException {
Statement stmt = null;
try {
Configuration configuration = ms.getConfiguration();
StatementHandler handler = configuration.newStatementHandler(this, ms, parameter, RowBounds.DEFAULT, null, null); //这里新建一个statement处理程序
stmt = prepareStatement(handler, ms.getStatementLog());　　//statement准备阶段，获取到有关数据库的信息等
return handler.update(stmt);
} finally {
closeStatement(stmt);
}
}

------------------------------newStatementHandler具体执行过程-------------------------------------------------------------------------------------------------------

public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds

rowBounds, ResultHandler resultHandler, BoundSql boundSql) {　

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
return statementHandler;

}

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public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {

switch (ms.getStatementType()) {　　　　　　　　　　　　　　　　　　　　　　　　　　　　//PREPARED(默认)
case STATEMENT:
delegate = new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
break;
case PREPARED:
delegate = new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
break;
case CALLABLE:
delegate = new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
break;
default:
throw new ExecutorException("Unknown statement type: " + ms.getStatementType());
}

}

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public PreparedStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
super(executor, mappedStatement, parameter, rowBounds, resultHandler, boundSql);
}

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protected BaseStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
this.configuration = mappedStatement.getConfiguration();
this.executor = executor;
this.mappedStatement = mappedStatement;
this.rowBounds = rowBounds;

this.typeHandlerRegistry = configuration.getTypeHandlerRegistry();
this.objectFactory = configuration.getObjectFactory();

if (boundSql == null) { // issue #435, get the key before calculating the statement
generateKeys(parameterObject);
boundSql = mappedStatement.getBoundSql(parameterObject);　　　　//获取boundSql
}

this.boundSql = boundSql;

this.parameterHandler = configuration.newParameterHandler(mappedStatement, parameterObject, boundSql);　　//参数处理器
this.resultSetHandler = configuration.newResultSetHandler(executor, mappedStatement, rowBounds, parameterHandler, resultHandler, boundSql);//结果处理器
}

------------------真正执行插入的核心代码在PreparedStatementHandler类中------------------------

public int update(Statement statement) throws SQLException {
PreparedStatement ps = (PreparedStatement) statement;
ps.execute();　　　　　　　　　　　　　　　　　　　　　　　　　　//执行插入
int rows = ps.getUpdateCount();
Object parameterObject = boundSql.getParameterObject();
KeyGenerator keyGenerator = mappedStatement.getKeyGenerator();
keyGenerator.processAfter(executor, mappedStatement, ps, parameterObject);
return rows;　　　　　　　　　　　　　　　　　　　　　　　　　　//返回执行的结果
}

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修改源码分析--update()同增加操作

删除源码分析--delete()同update()操作

public int delete(String statement, Object parameter) {
return update(statement, parameter);
}

查询源码分析--selectList()

public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
try {
MappedStatement ms = configuration.getMappedStatement(statement);　　　　　　　　//获取到对应的ms
List<E> result = executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
return result;
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error querying database. Cause: " + e, e);
} finally {
ErrorContext.instance().reset();
}
}

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public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
BoundSql boundSql = ms.getBoundSql(parameterObject);　　　　　　　　　　　　　　　　　　　　　　　　　　//获取到boundSql
CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql);
return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);　　　　　　　　　　　　　　　　//执行查询
}

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public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
throws SQLException {
Cache cache = ms.getCache();　　　　　　　　　　　　　　　　//首先获取缓存
if (cache != null) {　　　　　　　　　　　　　　　　　　　　　　//如果缓存不为空，清除缓存
flushCacheIfRequired(ms);
if (ms.isUseCache() && resultHandler == null) {
ensureNoOutParams(ms, parameterObject, boundSql);
@SuppressWarnings("unchecked")
List<E> list = (List<E>) tcm.getObject(cache, key);
if (list == null) {
list = delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
tcm.putObject(cache, key, list); // issue #578. Query must be not synchronized to prevent deadlocks
}
return list;
}
}
return delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}

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public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
if (closed) throw new ExecutorException("Executor was closed.");
if (queryStack == 0 && ms.isFlushCacheRequired()) {
clearLocalCache();　　　　　　　　　　　　　　　　　　//清除一级缓存
}
List<E> list;
try {
queryStack++;
list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
if (list != null) {　　　　　　　　　　　　　　　　　　　　　　　　　　　　
handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);　　　　　　//从缓存中获取查询结果
} else {
list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);　　//从数据库中获取查询结果
}
} finally {
queryStack--;
}
if (queryStack == 0) {
for (DeferredLoad deferredLoad : deferredLoads) {
deferredLoad.load();
}
deferredLoads.clear(); // issue #601
if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
clearLocalCache(); // issue #482
}
}
return list;
}