写了个go结构体映射工具



```go

package main

import (
	"github.com/yowayimono/mapper/mapper"
	"reflect"
	"testing"
)

type SourceStruct struct {
	Username string
	Password string
	Phone    string
}

type TargetStruct struct {
	Username string
	Password string
	Phone    string
}

type NestedStruct struct {
	Field1 string
	Field2 int
}

type SourceStructWithNested struct {
	Username string
	Password string
	Phone    string
	Nested   NestedStruct
}

type TargetStructWithNested struct {
	Username string
	Password string

	Nested NestedStruct
}

func TestMapFields(t *testing.T) {
	source := SourceStructWithNested{
		Username: "john",
		Password: "password123",
		Phone:    "1234567890",
		Nested: NestedStruct{
			Field1: "1234",
			Field2: 18,
		},
	}

	target := TargetStructWithNested{}

	mapper.Maps(&source, &target)

	expected := TargetStructWithNested{
		Username: "john",
		Password: "password123",
		Nested: NestedStruct{
			Field1: "1234",
			Field2: 18,
		},
	}

	if !reflect.DeepEqual(target, expected) {
		t.Errorf("MapFields did not map the fields correctly. Expected: %v, got: %v", expected, target)
	}
}
```

支持嵌套映射结构体，支持标签
```go
package main

import (
	"github.com/yowayimono/mapper/mapper"
	"reflect"
	"testing"
)

type Source struct {
	ID   int
	Name string
}

type Target struct {
	IDY int `mapper:"ID"`
}

func TestMap(t *testing.T) {
	source := &Source{
		ID:   1,
		Name: "John Doe",
	}

	target := &Target{}

	mapper.Map(source, target)

	expected := Target{
		IDY: 1,
	}

	if !reflect.DeepEqual(*target, expected) {
		t.Errorf("Mapping failed. Expected %+v, got %+v", expected, *target)
	}
}
```

标签映射还不支持嵌套

go结构体映射工具

English learn

Tomcat源码学习13  --总结（1）


![image.png](/static/img/a8ccc1180b30bced021b10e49b415376.image.webp)

Tomcat源码学习 --对比jetty

## Engine实现类
Engine 本质是一个容器，因此它继承了 ContainerBase 基类，并且实现了 Engine 接口。

Engine 的子容器是 Host，所以它持有了一个 Host 容器的数组，这些功能都被抽象到了 ContainerBase 中，ContainerBase 中有这样一个数据结构：

ContainerBase 用 HashMap 保存了它的子容器，并且 ContainerBase 还实现了子容器的“增删改查”，甚至连子组件的启动和停止都提供了默认实现，比如 ContainerBase 会用专门的线程池来启动子容器。
```java
public class StandardEngine extends ContainerBase implements Engine {

    private static final Log log = LogFactory.getLog(StandardEngine.class);




    // ----------------------------------------------------------- Constructors

    /**
     * Create a new StandardEngine component with the default basic Valve.
     */
    public StandardEngine() {
        pipeline.setBasic(new StandardEngineValve());
        /* Set the jvmRoute using the system property jvmRoute */
        try {
            setJvmRoute(System.getProperty("jvmRoute"));
        } catch (Exception ex) {
            log.warn(sm.getString("standardEngine.jvmRouteFail"));
        }
        // By default, the engine will hold the reloading thread
        backgroundProcessorDelay = 10;
    }


    // ----------------------------------------------------- Instance Variables

    /**
     * Host name to use when no server host, or an unknown host, is specified in the request.
     */
    private String defaultHost = null;


    /**
     * The <code>Service</code> that owns this Engine, if any.
     */
    private Service service = null;

    /**
     * The JVM Route ID for this Tomcat instance. All Route ID's must be unique across the cluster.
     */
    private String jvmRouteId;

    /**
     * Default access log to use for request/response pairs where we can't ID the intended host and context.
     */
    private final AtomicReference<AccessLog> defaultAccessLog = new AtomicReference<>();

    // ------------------------------------------------------------- Properties

    /**
     * Obtain the configured Realm and provide a default Realm implementation when no explicit configuration is set.
     *
     * @return configured realm, or a {@link NullRealm} by default
     */
    @Override
    public Realm getRealm() {
        Realm configured = super.getRealm();
        // If no set realm has been called - default to NullRealm
        // This can be overridden at engine, context and host level
        if (configured == null) {
            configured = new NullRealm();
            this.setRealm(configured);
        }
        return configured;
    }


    /**
     * Return the default host.
     */
    @Override
    public String getDefaultHost() {
        return defaultHost;
    }


    /**
     * Set the default host.
     *
     * @param host The new default host
     */
    @Override
    public void setDefaultHost(String host) {

        String oldDefaultHost = this.defaultHost;
        if (host == null) {
            this.defaultHost = null;
        } else {
            this.defaultHost = host.toLowerCase(Locale.ENGLISH);
        }
        if (getState().isAvailable()) {
            service.getMapper().setDefaultHostName(host);
        }
        support.firePropertyChange("defaultHost", oldDefaultHost, this.defaultHost);

    }


    /**
     * Set the cluster-wide unique identifier for this Engine. This value is only useful in a load-balancing scenario.
     * <p>
     * This property should not be changed once it is set.
     */
    @Override
    public void setJvmRoute(String routeId) {
        jvmRouteId = routeId;
    }


    /**
     * Retrieve the cluster-wide unique identifier for this Engine. This value is only useful in a load-balancing
     * scenario.
     */
    @Override
    public String getJvmRoute() {
        return jvmRouteId;
    }


    /**
     * Return the <code>Service</code> with which we are associated (if any).
     */
    @Override
    public Service getService() {
        return this.service;
    }


    /**
     * Set the <code>Service</code> with which we are associated (if any).
     *
     * @param service The service that owns this Engine
     */
    @Override
    public void setService(Service service) {
        this.service = service;
    }

    // --------------------------------------------------------- Public Methods


    /**
     * Add a child Container, only if the proposed child is an implementation of Host.
     *
     * @param child Child container to be added
     */
    @Override
    public void addChild(Container child) {

        if (!(child instanceof Host)) {
            throw new IllegalArgumentException(sm.getString("standardEngine.notHost"));
        }
        super.addChild(child);

    }


    /**
     * Disallow any attempt to set a parent for this Container, since an Engine is supposed to be at the top of the
     * Container hierarchy.
     *
     * @param container Proposed parent Container
     */
    @Override
    public void setParent(Container container) {

        throw new IllegalArgumentException(sm.getString("standardEngine.notParent"));

    }


    @Override
    protected void initInternal() throws LifecycleException {
        // Ensure that a Realm is present before any attempt is made to start
        // one. This will create the default NullRealm if necessary.
        getRealm();
        super.initInternal();
    }


    /**
     * Start this component and implement the requirements of
     * {@link org.apache.catalina.util.LifecycleBase#startInternal()}.
     *
     * @exception LifecycleException if this component detects a fatal error that prevents this component from being
     *                                   used
     */
    @Override
    protected synchronized void startInternal() throws LifecycleException {

        // Log our server identification information
        if (log.isInfoEnabled()) {
            log.info(sm.getString("standardEngine.start", ServerInfo.getServerInfo()));
        }

        // Standard container startup
        super.startInternal();
    }


    /**
     * Override the default implementation. If no access log is defined for the Engine, look for one in the Engine's
     * default host and then the default host's ROOT context. If still none is found, return the default NoOp access
     * log.
     */
    @Override
    public void logAccess(Request request, Response response, long time, boolean useDefault) {

        boolean logged = false;

        if (getAccessLog() != null) {
            accessLog.log(request, response, time);
            logged = true;
        }

        if (!logged && useDefault) {
            AccessLog newDefaultAccessLog = defaultAccessLog.get();
            if (newDefaultAccessLog == null) {
                // If we reached this point, this Engine can't have an AccessLog
                // Look in the defaultHost
                Host host = (Host) findChild(getDefaultHost());
                Context context = null;
                if (host != null && host.getState().isAvailable()) {
                    newDefaultAccessLog = host.getAccessLog();

                    if (newDefaultAccessLog != null) {
                        if (defaultAccessLog.compareAndSet(null, newDefaultAccessLog)) {
                            AccessLogListener l = new AccessLogListener(this, host, null);
                            l.install();
                        }
                    } else {
                        // Try the ROOT context of default host
                        context = (Context) host.findChild("");
                        if (context != null && context.getState().isAvailable()) {
                            newDefaultAccessLog = context.getAccessLog();
                            if (newDefaultAccessLog != null) {
                                if (defaultAccessLog.compareAndSet(null, newDefaultAccessLog)) {
                                    AccessLogListener l = new AccessLogListener(this, null, context);
                                    l.install();
                                }
                            }
                        }
                    }
                }

                if (newDefaultAccessLog == null) {
                    newDefaultAccessLog = new NoopAccessLog();
                    if (defaultAccessLog.compareAndSet(null, newDefaultAccessLog)) {
                        AccessLogListener l = new AccessLogListener(this, host, context);
                        l.install();
                    }
                }
            }

            newDefaultAccessLog.log(request, response, time);
        }
    }


    /**
     * Return the parent class loader for this component.
     */
    @Override
    public ClassLoader getParentClassLoader() {
        if (parentClassLoader != null) {
            return parentClassLoader;
        }
        if (service != null) {
            return service.getParentClassLoader();
        }
        return ClassLoader.getSystemClassLoader();
    }


    @Override
    public File getCatalinaBase() {
        if (service != null) {
            Server s = service.getServer();
            if (s != null) {
                File base = s.getCatalinaBase();
                if (base != null) {
                    return base;
                }
            }
        }
        // Fall-back
        return super.getCatalinaBase();
    }


    @Override
    public File getCatalinaHome() {
        if (service != null) {
            Server s = service.getServer();
            if (s != null) {
                File base = s.getCatalinaHome();
                if (base != null) {
                    return base;
                }
            }
        }
        // Fall-back
        return super.getCatalinaHome();
    }


    // -------------------- JMX registration --------------------

    @Override
    protected String getObjectNameKeyProperties() {
        return "type=Engine";
    }


    @Override
    protected String getDomainInternal() {
        return getName();
    }


    // ----------------------------------------------------------- Inner classes
    protected static final class NoopAccessLog implements AccessLog {

        @Override
        public void log(Request request, Response response, long time) {
            // NOOP
        }

        @Override
        public void setRequestAttributesEnabled(boolean requestAttributesEnabled) {
            // NOOP

        }

        @Override
        public boolean getRequestAttributesEnabled() {
            // NOOP
            return false;
        }
    }

    protected static final class AccessLogListener
            implements PropertyChangeListener, LifecycleListener, ContainerListener {

        private final StandardEngine engine;
        private final Host host;
        private final Context context;
        private volatile boolean disabled = false;

        public AccessLogListener(StandardEngine engine, Host host, Context context) {
            this.engine = engine;
            this.host = host;
            this.context = context;
        }

        public void install() {
            engine.addPropertyChangeListener(this);
            if (host != null) {
                host.addContainerListener(this);
                host.addLifecycleListener(this);
            }
            if (context != null) {
                context.addLifecycleListener(this);
            }
        }

        private void uninstall() {
            disabled = true;
            if (context != null) {
                context.removeLifecycleListener(this);
            }
            if (host != null) {
                host.removeLifecycleListener(this);
                host.removeContainerListener(this);
            }
            engine.removePropertyChangeListener(this);
        }

        @Override
        public void lifecycleEvent(LifecycleEvent event) {
            if (disabled) {
                return;
            }

            String type = event.getType();
            if (AFTER_START_EVENT.equals(type) || BEFORE_STOP_EVENT.equals(type) || BEFORE_DESTROY_EVENT.equals(type)) {
                // Container is being started/stopped/removed
                // Force re-calculation and disable listener since it won't
                // be re-used
                engine.defaultAccessLog.set(null);
                uninstall();
            }
        }

        @Override
        public void propertyChange(PropertyChangeEvent evt) {
            if (disabled) {
                return;
            }
            if ("defaultHost".equals(evt.getPropertyName())) {
                // Force re-calculation and disable listener since it won't
                // be re-used
                engine.defaultAccessLog.set(null);
                uninstall();
            }
        }

        @Override
        public void containerEvent(ContainerEvent event) {
            // Only useful for hosts
            if (disabled) {
                return;
            }
            if (ADD_CHILD_EVENT.equals(event.getType())) {
                Context context = (Context) event.getData();
                if (context.getPath().isEmpty()) {
                    // Force re-calculation and disable listener since it won't
                    // be re-used
                    engine.defaultAccessLog.set(null);
                    uninstall();
                }
            }
        }
    }
}

```