functionalias.java

非常棒的java数据库

/*
 * Copyright 2004-2008 H2 Group. Licensed under the H2 License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.engine;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.sql.Connection;
import java.sql.SQLException;

import org.h2.command.Parser;
import org.h2.constant.ErrorCode;
import org.h2.expression.Expression;
import org.h2.message.Message;
import org.h2.message.Trace;
import org.h2.table.Table;
import org.h2.value.DataType;
import org.h2.value.Value;
import org.h2.value.ValueNull;

/**
 * Represents a user defined function, or alias.
 */
public class FunctionAlias extends DbObjectBase {

    private boolean hasConnectionParam;
    private String className;
    private String methodName;
    private Method javaMethod;
    private int paramCount;
    private int dataType;

    public FunctionAlias(Database db, int id, String name, String javaClassMethod, boolean force) throws SQLException {
        super(db, id, name, Trace.FUNCTION);
        int paren = javaClassMethod.indexOf('(');
        int lastDot = javaClassMethod.lastIndexOf('.', paren < 0 ? javaClassMethod.length() : paren);
        if (lastDot < 0) {
            throw Message.getSQLException(ErrorCode.SYNTAX_ERROR_1, javaClassMethod);
        }
        className = javaClassMethod.substring(0, lastDot);
        methodName = javaClassMethod.substring(lastDot + 1);
        try {
            // at least try to load the class, otherwise the data type is not
            // initialized if it could be
            load();
        } catch (SQLException e) {
            if (!force) {
                throw e;
            }
        }
    }

    private synchronized void load() throws SQLException {
        if (javaMethod != null) {
            return;
        }
        Class javaClass = database.loadUserClass(className);
        Method[] methods = javaClass.getMethods();
        for (int i = 0; i < methods.length; i++) {
            Method m = methods[i];
            if (!Modifier.isStatic(m.getModifiers())) {
                continue;
            }
            if (m.getName().equals(methodName)) {
                javaMethod = m;
                break;
            } else if (getMethodSignature(m).equals(methodName)) {
                javaMethod = m;
                break;
            }
        }
        if (javaMethod == null) {
            throw Message.getSQLException(ErrorCode.METHOD_NOT_FOUND_1, methodName + " (" + className + ")");
        }
        Class[] paramClasses = javaMethod.getParameterTypes();
        paramCount = paramClasses.length;
        if (paramCount > 0) {
            Class paramClass = paramClasses[0];
            if (Connection.class.isAssignableFrom(paramClass)) {
                hasConnectionParam = true;
                paramCount--;
            }
        }
        Class returnClass = javaMethod.getReturnType();
        dataType = DataType.getTypeFromClass(returnClass);
    }

    private String getMethodSignature(Method m) {
        StringBuffer buff = new StringBuffer();
        buff.append(m.getName());
        buff.append('(');
        Class[] params = m.getParameterTypes();
        for (int i = 0; i < params.length; i++) {
            if (i > 0) {
                buff.append(", ");
            }
            Class p = params[i];
            if (p.isArray()) {
                buff.append(p.getComponentType().getName());
                buff.append("[]");
            } else {
                buff.append(p.getName());
            }
        }
        buff.append(')');
        return buff.toString();
    }

    public Class[] getColumnClasses() throws SQLException {
        load();
        return javaMethod.getParameterTypes();
    }

    public int getDataType() {
        return dataType;
    }

    public String getCreateSQLForCopy(Table table, String quotedName) {
        throw Message.getInternalError();
    }

    public String getDropSQL() {
        return "DROP ALIAS IF EXISTS " + getSQL();
    }

    public String getCreateSQL() {
        StringBuffer buff = new StringBuffer();
        buff.append("CREATE FORCE ALIAS ");
        buff.append(getSQL());
        buff.append(" FOR ");
        buff.append(Parser.quoteIdentifier(className + "." + methodName));
        return buff.toString();
    }

    public int getType() {
        return DbObject.FUNCTION_ALIAS;
    }

    public synchronized void removeChildrenAndResources(Session session) throws SQLException {
        database.removeMeta(session, getId());
        className = methodName = null;
        javaMethod = null;
        invalidate();
    }

    public void checkRename() throws SQLException {
        throw Message.getUnsupportedException();
    }

    public Value getValue(Session session, Expression[] args) throws SQLException {
        return getValue(session, args, false);
    }

    /**
     * Call the user defined function and return the value.
     * 
     * @param session the session
     * @param args the argument list
     * @param columnList true if the function should only return the column list
     * @return the value
     */
    public synchronized Value getValue(Session session, Expression[] args, boolean columnList) throws SQLException {
        load();
        Class[] paramClasses = javaMethod.getParameterTypes();
        Object[] params = new Object[paramClasses.length];
        int p = 0;
        if (hasConnectionParam && params.length > 0) {
            params[p++] = session.createConnection(columnList);
        }
        for (int a = 0; a < args.length && p < params.length; a++, p++) {
            Class paramClass = paramClasses[p];
            int type = DataType.getTypeFromClass(paramClass);
            Value v = args[a].getValue(session);
            v = v.convertTo(type);
            Object o = v.getObject();
            if (o == null) {
                if (paramClass.isPrimitive()) {
                    if (columnList) {
                        // if the column list is requested, the parameters may
                        // be null
                        // need to set to default value otherwise the function
                        // can't be called at all
                        o = DataType.getDefaultForPrimitiveType(paramClass);
                    } else {
                        // NULL for a java primitive: return NULL
                        return ValueNull.INSTANCE;
                    }
                }
            } else {
                if (!paramClass.isAssignableFrom(o.getClass()) && !paramClass.isPrimitive()) {
                    o = DataType.convertTo(session, session.createConnection(false), v, paramClass);
                }
            }
            params[p] = o;
        }
        boolean old = session.getAutoCommit();
        try {
            session.setAutoCommit(false);
            try {
                Object returnValue;
                returnValue = javaMethod.invoke(null, params);
                if (returnValue == null) {
                    return ValueNull.INSTANCE;
                }
                Value ret = DataType.convertToValue(session, returnValue, dataType);
                return ret.convertTo(dataType);
            } catch (Exception e) {
                throw Message.convert(e);
            }
        } finally {
            session.setAutoCommit(old);
        }
    }

    public int getParameterCount() throws SQLException {
        load();
        return paramCount;
    }

    public String getJavaClassName() {
        return this.className;
    }

    public String getJavaMethodName() {
        return this.methodName;
    }

    public boolean hasConnectionParam() {
        return this.hasConnectionParam;
    }

}