第六篇文章我们拿到了Mapper的一个代理对象,我们知道代理对象的执行其实是交给了InvocationHandler来处理的,也就是我们的MapperProxy对象。我们看一下invoke方法:
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
if (Object.class.equals(method.getDeclaringClass())) {
return method.invoke(this, args);
} else if (isDefaultMethod(method)) {
return invokeDefaultMethod(proxy, method, args);
}
} catch (Throwable t) {
throw ExceptionUtil.unwrapThrowable(t);
}
//我们根据当前的方法在缓存中获取MapperMethod
final MapperMethod mapperMethod = cachedMapperMethod(method);
//执行相应的方法
return mapperMethod.execute(sqlSession, args);
}
1.获取MapperMethod
private MapperMethod cachedMapperMethod(Method method) {
//在缓存中获取
MapperMethod mapperMethod = methodCache.get(method);
if (mapperMethod == null) {
//如果没有生成mapperMethod
mapperMethod = new MapperMethod(mapperInterface, method, sqlSession.getConfiguration());
//加入当前缓存
methodCache.put(method, mapperMethod);
}
return mapperMethod;
}
public MapperMethod(Class<?> mapperInterface, Method method, Configuration config) {
//初始化SqlCommand对象
this.command = new SqlCommand(config, mapperInterface, method);
//初始化MethodSignature对象
this.method = new MethodSignature(config, mapperInterface, method);
}
1.1初始化SqlCommand对象
public SqlCommand(Configuration configuration, Class<?> mapperInterface, Method method) {
//获取当前方法名称
final String methodName = method.getName();
//获取当前方法 所属的类
final Class<?> declaringClass = method.getDeclaringClass();
//这里获取MappedStatement 也就是我们解析mapper时生成的
MappedStatement ms = resolveMappedStatement(mapperInterface, methodName, declaringClass,
configuration);
if (ms == null) {
if (method.getAnnotation(Flush.class) != null) {
name = null;
type = SqlCommandType.FLUSH;
} else {
throw new BindingException("Invalid bound statement (not found): "
+ mapperInterface.getName() + "." + methodName);
}
} else {
//这里获取MappedStatement 的ID
name = ms.getId();
//当前SQL的类型(增删改查)
type = ms.getSqlCommandType();
if (type == SqlCommandType.UNKNOWN) {
throw new BindingException("Unknown execution method for: " + name);
}
}
}
1.1.1获取MappedStatement
private MappedStatement resolveMappedStatement(Class<?> mapperInterface, String methodName,
Class<?> declaringClass, Configuration configuration) {
//组装ID 其实就是 之前设定的namespace.定义的ID(方法名称)
String statementId = mapperInterface.getName() + "." + methodName;
//根据ID在缓存中获取到了 直接返回
if (configuration.hasStatement(statementId)) {
return configuration.getMappedStatement(statementId);
} else if (mapperInterface.equals(declaringClass)) {
return null;
}
//如果当前方法不在当前接口中 往父类接口找
for (Class<?> superInterface : mapperInterface.getInterfaces()) {
if (declaringClass.isAssignableFrom(superInterface)) {
MappedStatement ms = resolveMappedStatement(superInterface, methodName,
declaringClass, configuration);
if (ms != null) {
return ms;
}
}
}
return null;
}
}
1.2初始化MethodSignature对象
public MethodSignature(Configuration configuration, Class<?> mapperInterface, Method method) {
//获取当前方法的返回类型
Type resolvedReturnType = TypeParameterResolver.resolveReturnType(method, mapperInterface);
if (resolvedReturnType instanceof Class<?>) {
this.returnType = (Class<?>) resolvedReturnType;
} else if (resolvedReturnType instanceof ParameterizedType) {
//泛型
this.returnType = (Class<?>) ((ParameterizedType) resolvedReturnType).getRawType();
} else {
this.returnType = method.getReturnType();
}
//是不是没有返回值 void类型
this.returnsVoid = void.class.equals(this.returnType);
//返回的类型 是不是集合或者数组
this.returnsMany = configuration.getObjectFactory().isCollection(this.returnType) || this.returnType.isArray();
this.returnsCursor = Cursor.class.equals(this.returnType);
//返回的map类型
this.mapKey = getMapKey(method);
this.returnsMap = this.mapKey != null;
this.rowBoundsIndex = getUniqueParamIndex(method, RowBounds.class);
this.resultHandlerIndex = getUniqueParamIndex(method, ResultHandler.class);
this.paramNameResolver = new ParamNameResolver(configuration, method);
}
2.执行相应的方法
public Object execute(SqlSession sqlSession, Object[] args) {
Object result;
//判断当前sql的类型(增删改查)
switch (command.getType()) {
case INSERT: {
//解析入参
Object param = method.convertArgsToSqlCommandParam(args);
//调用sqlSession的insert方法
//返回执行的行数
result = rowCountResult(sqlSession.insert(command.getName(), param));
break;
}
case UPDATE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.update(command.getName(), param));
break;
}
case DELETE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.delete(command.getName(), param));
break;
}
case SELECT:
//方法没有返回值
if (method.returnsVoid() && method.hasResultHandler()) {
executeWithResultHandler(sqlSession, args);
result = null;
} else if (method.returnsMany()) {
//返回的是集合或者数组
result = executeForMany(sqlSession, args);
} else if (method.returnsMap()) {
//返回的是map
result = executeForMap(sqlSession, args);
} else if (method.returnsCursor()) {
result = executeForCursor(sqlSession, args);
} else {
//返回的是单一对象
Object param = method.convertArgsToSqlCommandParam(args);
result = sqlSession.selectOne(command.getName(), param);
}
break;
case FLUSH:
result = sqlSession.flushStatements();
break;
default:
throw new BindingException("Unknown execution method for: " + command.getName());
}
if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
throw new BindingException("Mapper method '" + command.getName()
+ " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
}
return result;
}
这里可以最终调用的是sqlsession的方法,下一篇我们将详细介绍每一个方法。