How to build simple code generator in java

I want to build a simple code generator in java that can take database connection string and then create the model layer for each table in database , I don't know how can I do that , so if any one has any tutorial or links that may help me complete this task i will be thankful

Thanks in Advance

I have found a good example on code project that can take the database and make a good code generation for the tables in database , but unfortunately it is written in C# and also generate C# code

I don't know if it right to generate C# code and then convert them to java using any conversion so开发者_如何学Cftware , or the right thing is to try to modify it to generate java classes instead of C# classes

by the way the link for the example is http://www.codeproject.com/KB/codegen/TierGenerator.aspx

I need your advice as soon as you can

Thanks in Advance

If you want to implement your own code generator ...

In my experience ... using a template-based tool like Velocity or FreeMarker or JET reduces the effort in writing and maintaining source code generators.

Here are some relevant links:

• Template Code Generator : Apache Velocity - JET - JET2
• Template Code Generator Part 2 : FreeMarker
• Jet Tutorial - part 1, part2

Doing code generation using StringBuilder / String concatenation, is a lot of work (for a non-trivial code-generation task) and tends to give you a pile of code that is hard to read and hard to maintain. It is also more difficult to generate well-formatted (e.g, properly indented, line-wrapped) code, if that is relevant to your use-case.

For quick and simple code generator: Just write the java source code into a StringBuilder and dump it's content to a .java file. I never used third party libs for simple autogenerators:

StringBuilder sourceBuilder = new StringBuilder();
sourceBuilder.append("package com.example.beans;\n\n");
sourceBuilder.append("import java.util.*;\n\n");
sourceBuilder.append("public class MyBean {");

for (DBField dbField:getFieldsFromDatabaseModel) {  // this DBField class is pure fiction!
  // bean attribute
  sourceBuilder.append("\tprivate ")
               .append(dbField.getType)
               .append(toFieldName(dbField.getName()))
               .append(" = null;\n");

  // setter method
  sourceBuilder.append("\tpublic void ")
               .append(toSetterName(dbField.getName()))
               .append("(");
               .append(dbField.getType)
               .append(toFieldName(dbField.getName()))
               .append(")\n")
               .append("\t\tthis.")
               .append(dbField.getType)
               .append(" = ")
               .append(dbField.getType)
               .append(";\n\t}");

   // getter method ...
sourceBuilder.append("\t}\n}\n");

Don't reinvent the wheel, use an existing code generator. Telosys Tools does this kind of job : http://www.telosys.org/

It's an open source project, so you can also look inside if you want to reuse the generator engine (it works with Velocity templates)

Minuteproject is designed to meet this requirement. It reads database metadata, optionally (but in reality extremely useful) enrich the model and generate for any text based language (ex: java, c#, php, jsf, html, js etc...) You can benefit out of the box of shipped solutions (JPA2, Openxava, Primefaces)

But also you can:

• create additional artifacts (your own that match your architecture/design);
• decide there naming convention;
• if there are model, package, application, table, column, view specific;
• any artifact can find information on other artifacts if they want to correctly reference them.