聊聊shardingjdbc的WrapperAdapter

序

本文主要研究一下 sharding-jdbc 的 WrapperAdapter

Wrapper

jdk-12.jdk/Contents/Home/lib/src.zip!/java.sql/java/sql/Wrapper.java

public interface Wrapper {<T> T unwrap(java.lang.Class<T> iface) throws java.sql.SQLException;

    boolean isWrapperFor(java.lang.Class<?> iface) throws java.sql.SQLException;

}

• Wrapper 接口定义了 unwrap、isWrapperFor 方法

WrapperAdapter

incubator-shardingsphere-4.0.0-RC1/sharding-jdbc/sharding-jdbc-core/src/main/java/org/apache/shardingsphere/shardingjdbc/jdbc/adapter/WrapperAdapter.java

public abstract class WrapperAdapter implements Wrapper {private final Collection<JdbcMethodInvocation> jdbcMethodInvocations = new ArrayList<>();
    
    @SuppressWarnings("unchecked")
    @Override
    public final <T> T unwrap(final Class<T> iface) throws SQLException {if (isWrapperFor(iface)) {return (T) this;
        }
        throw new SQLException(String.format("[%s] cannot be unwrapped as [%s]", getClass().getName(), iface.getName()));
    }
    
    @Override
    public final boolean isWrapperFor(final Class<?> iface) {return iface.isInstance(this);
    }
    
    /**
     * record method invocation.
     * 
     * @param targetClass target class
     * @param methodName method name
     * @param argumentTypes argument types
     * @param arguments arguments
     */
    @SneakyThrows
    public final void recordMethodInvocation(final Class<?> targetClass, final String methodName, final Class<?>[] argumentTypes, final Object[] arguments) {jdbcMethodInvocations.add(new JdbcMethodInvocation(targetClass.getMethod(methodName, argumentTypes), arguments));
    }
    
    /**
     * Replay methods invocation.
     * 
     * @param target target object
     */
    public final void replayMethodsInvocation(final Object target) {for (JdbcMethodInvocation each : jdbcMethodInvocations) {each.invoke(target);
        }
    }
}

• WrapperAdapter 声明实现 java.sql.Wrapper 接口，它定义了 JdbcMethodInvocation 集合；recordMethodInvocation 方法会往 jdbcMethodInvocations 添加 JdbcMethodInvocation；replayMethodsInvocation 方法则会挨个执行 JdbcMethodInvocation 的 invoke 方法

JdbcMethodInvocation

incubator-shardingsphere-4.0.0-RC1/sharding-jdbc/sharding-jdbc-core/src/main/java/org/apache/shardingsphere/shardingjdbc/jdbc/adapter/invocation/JdbcMethodInvocation.java

@RequiredArgsConstructor
public class JdbcMethodInvocation {
    
    @Getter
    private final Method method;
    
    @Getter
    private final Object[] arguments;
    
    /**
     * Invoke JDBC method.
     * 
     * @param target target object
     */
    @SneakyThrows
    public void invoke(final Object target) {method.invoke(target, arguments);
    }
}

• JdbcMethodInvocation 的 invoke 方法执行的是 method.invoke

小结

WrapperAdapter 声明实现 java.sql.Wrapper 接口，它定义了 JdbcMethodInvocation 集合；recordMethodInvocation 方法会往 jdbcMethodInvocations 添加 JdbcMethodInvocation；replayMethodsInvocation 方法则会挨个执行 JdbcMethodInvocation 的 invoke 方法

doc

• WrapperAdapter