mybatis源码1.3 MapperMethod

先看一下MapperMethod类，SqlCommand和MethodSignature都是MapperMethod的静态内部类

public class MapperMethod {
    private final MapperMethod.SqlCommand command;
    private final MapperMethod.MethodSignature method;

    public MapperMethod(Class<?> mapperInterface, Method method, Configuration config) {
　　　　　　//SqlCommand中封装了sql的类型，insert，update....    MethodSignature封装了方法的参数和返回值信息
        this.command = new MapperMethod.SqlCommand(config, mapperInterface, method);
        this.method = new MapperMethod.MethodSignature(config, mapperInterface, method);
    }
}

回到MapperProxy中的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);
            }

            if (method.isDefault()) {
                return this.invokeDefaultMethod(proxy, method, args);
            }
        } catch (Throwable var5) {
            throw ExceptionUtil.unwrapThrowable(var5);
        }
　　　　 也就是判断MapperPorxy中的methodCache中是否又该值，MapperProxy中methodCache是一个Map<Mehtod,MapperMethod>
　　　　cachedMapperMethod判断当前方法是否已经执行过了，如果map不能找到该元素，则说明没有执行过，会创建一个MapperMethod,并添加到methodCache中
        MapperMethod mapperMethod = this.cachedMapperMethod(method);
        return mapperMethod.execute(this.sqlSession, args);
    }
    private MapperMethod cachedMapperMethod(Method method) {
        return (MapperMethod)this.methodCache.computeIfAbsent(method, (k) -> {
            return new MapperMethod(this.mapperInterface, method, this.sqlSession.getConfiguration());
        });
    }

接下来进入  mapperMethod.execute(this.sqlSession, args)方法

    public Object execute(SqlSession sqlSession, Object[] args) {
        Object result;
        Object param;
        switch(this.command.getType()) {
        case INSERT:
            param = this.method.convertArgsToSqlCommandParam(args);
            result = this.rowCountResult(sqlSession.insert(this.command.getName(), param));
            break;
        case UPDATE:
            param = this.method.convertArgsToSqlCommandParam(args);
            result = this.rowCountResult(sqlSession.update(this.command.getName(), param));
            break;
        case DELETE:
            param = this.method.convertArgsToSqlCommandParam(args);
            result = this.rowCountResult(sqlSession.delete(this.command.getName(), param));
            break;
        case SELECT:
            if (this.method.returnsVoid() && this.method.hasResultHandler()) {
                this.executeWithResultHandler(sqlSession, args);
                result = null;
            } else if (this.method.returnsMany()) {
                result = this.executeForMany(sqlSession, args);
            } else if (this.method.returnsMap()) {
                result = this.executeForMap(sqlSession, args);
            } else if (this.method.returnsCursor()) {
                result = this.executeForCursor(sqlSession, args);
            } else {
                param = this.method.convertArgsToSqlCommandParam(args);
                result = sqlSession.selectOne(this.command.getName(), param);
                if (this.method.returnsOptional() && (result == null || !this.method.getReturnType().equals(result.getClass()))) {
                    result = Optional.ofNullable(result);
                }
            }
            break;
        case FLUSH:
            result = sqlSession.flushStatements();
            break;
        default:
            throw new BindingException("Unknown execution method for: " + this.command.getName());
        }

        if (result == null && this.method.getReturnType().isPrimitive() && !this.method.returnsVoid()) {
            throw new BindingException("Mapper method '" + this.command.getName() + " attempted to return null from a method with a primitive return type (" + this.method.getReturnType() + ").");
        } else {
            return result;
        }
    }