TableCreator.java

//: annotations/database/TableCreator.java
// Reflection-based annotation processor.
// {Args: annotations.database.Member}
package ch20annotation.database;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;

/**
 * 实现复杂的注解处理器
 */
public class TableCreator {
    /**
     * 实现复杂的注解处理器，根据domain类的注解自动生成建表SQL语句
     *
     * @throws ClassNotFoundException
     */
    public static void processAnnotation() throws ClassNotFoundException {
        String[] args = {"ch20annotation.database.Member"};
        if (args.length < 1) {
            System.out.println("arguments: annotated classes");
            System.exit(0);
        }
        for (String className : args) {
            Class<?> cl = Class.forName(className);
            DBTable dbTable = cl.getAnnotation(DBTable.class);
            if (dbTable == null) {
                System.out.println("No DBTable annotations in class "
                        + className);
                continue;
            }
            String tableName = dbTable.name();
            // If the name is empty, use the Class name:
            if (tableName.length() < 1)
                tableName = cl.getName().toUpperCase();
            List<String> columnDefs = new ArrayList<String>();
            for (Field field : cl.getDeclaredFields()) {
                String columnName = null;
                Annotation[] anns = field.getDeclaredAnnotations();
                if (anns.length < 1)
                    continue; // Not a db table column
                if (anns[0] instanceof SQLInteger) {
                    SQLInteger sInt = (SQLInteger) anns[0];
                    // Use field name if name not specified
                    if (sInt.name().length() < 1)
                        columnName = field.getName().toUpperCase();
                    else
                        columnName = sInt.name();
                    columnDefs.add(columnName + " INT"
                            + getConstraints(sInt.constraints()));
                }
                if (anns[0] instanceof SQLString) {
                    SQLString sString = (SQLString) anns[0];
                    // Use field name if name not specified.
                    if (sString.name().length() < 1)
                        columnName = field.getName().toUpperCase();
                    else
                        columnName = sString.name();
                    columnDefs.add(columnName + " VARCHAR(" + sString.value()
                            + ")" + getConstraints(sString.constraints()));
                }
                StringBuilder createCommand = new StringBuilder("CREATE TABLE "
                        + tableName + "(");
                for (String columnDef : columnDefs)
                    createCommand.append("\n    " + columnDef + ",");
                // Remove trailing comma
                String tableCreate = createCommand.substring(0,
                        createCommand.length() - 1)
                        + ");";
                System.out.println("Table Creation SQL for " + className
                        + " is :\n" + tableCreate);
            }
        }
    }

    private static String getConstraints(Constraints con) {
        String constraints = "";
        if (!con.allowNull())
            constraints += " NOT NULL";
        if (con.primaryKey())
            constraints += " PRIMARY KEY";
        if (con.unique())
            constraints += " UNIQUE";
        return constraints;
    }
} /*
 * Output: Table Creation SQL for annotations.database.Member is : CREATE TABLE
 * MEMBER( FIRSTNAME VARCHAR(30)); Table Creation SQL for
 * annotations.database.Member is : CREATE TABLE MEMBER( FIRSTNAME VARCHAR(30),
 * LASTNAME VARCHAR(50)); Table Creation SQL for annotations.database.Member is
 * : CREATE TABLE MEMBER( FIRSTNAME VARCHAR(30), LASTNAME VARCHAR(50), AGE INT);
 * Table Creation SQL for annotations.database.Member is : CREATE TABLE MEMBER(
 * FIRSTNAME VARCHAR(30), LASTNAME VARCHAR(50), AGE INT, HANDLE VARCHAR(30)
 * PRIMARY KEY);
 */// :~