Clinton R. Begincbegin@apache.org

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Dealing with Enterprise Database Challenges

Featuring the Apache iBATIS Data Mapping Framework

Clinton Begincbegin@thoughtworks.com

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Demo…

Just move data from here to there.

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ScopeThe Challenges

• Ownership, access, complexity, normalization, skinny design.

iBATIS Data Mapping Framework

• Introduction, SQL Mapping defined, examples.

SQL

• Is it still relevant?

iBATIS is a hybrid solution

• Features, qualities, competition, other solutions.

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The Challenges

“Welcome, to the real world.”

– go for the red pill

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Challenges of PoliticsDatabase ownership and control

Change management

Cost allocation – who pays for changes?

No “developer” access to design

Proprietary/3rd Party – legal issues

Agile methods vs. legacy methods

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iBATIS isolates the data model, the SQL, the work and the responsibility. In doing so, it isolates much of the politics surrounding the enterprise database as well.

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Challenges of ImperfectionDenormalized models

Super-normalized models

Modeled Value Entities

Thin data models (rows vs. columns)

Implicit relationships

Overcomplicated relationships

Null Values (?)

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Thin data model

Group Name Type Value

1 Street String 12 Some St

1 City String Modesto

1 State String California

1 Zip String 12345

2 Street String 543 Other St

2 City String Fresno

2 State String California

2 Zip String 34332

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iBATIS works even when the data model does not map to the object model.

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Challenges of Legacy and complexityToo many tables to map

Encoded Fields

No primary keys

Hierarchical

ERP systems

Temporal databases

“600 tables” – moderate size (?)

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iBATIS allows you to build modern applications on top of legacy databases by allowing you more freedom to define and tune your mappings that deal with “unique” databases.

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Challenges of TechnologyDistributed transactions

Distributed caching

Vendor specific database features

Multiple databases w/ single object model

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iBATIS supports advanced enterprise features and allows you to take full advantage of the investment you’ve made in your relational database management system.

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An Introduction to Apache iBATIS

SQL Mapping defined…

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SQL Mapping

Concept

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SELECT FIRST_NAME, LAST_NAME

FROM EMPLOYEE

WHERE EMPLOYEE_NUMBER = ‘1234’

INPUT

OUTPUT OUTPUT

SQL as a Black Box

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SQL MappingMaps objects to SQL statements• NOT Classes to Tables

Fully functional SQL via named statements• NOT generated SQL (although that’s possible)

For example…

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id : inttotal : BigDecimalpst : BigDecimalgst : BigDecimllineItems : Collectiondate : Date

Order

id : intproduct : Productorder : Ordercost : BigDecimalretail : BigDecimal

LineItem id : intname : Stringdescription : Stringcost : BigDecimalretail : BigDeciml

Product

Order

LineItemProduct

Mapping Layer

TABLES

CLASSES

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id : inttotal : BigDecimalpst : BigDecimalgst : BigDecimllineItems : Collectiondate : Date

Order

id : intproduct : Productorder : Ordercost : BigDecimalretail : BigDecimal

LineItem id : intname : Stringdescription : Stringcost : BigDecimalretail : BigDeciml

Product

Order

LineItemProduct

Mapping Layer

SQL

TABLES

CLASSES

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The Product Table

PRODUCT

PRODUCT_ID INTEGER PK, NN

NAME VARCHAR NN

DESCRIPTION TEXT NN

COST MONEY NN

RETAIL MONEY NN

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The Product Class

public class Product {

private int id;

private String name;

private String description;

private BigDecimal cost;

private BigDecimal retail;

//…getters/setters implied

}

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The SQL<select

id=“getProduct" parameterClass=“int”resultClass="examples.domain.Product">

SELECT

PRODUCT_ID as id,

NAME,

DESCRIPTION,

COST,

RETAIL,

FROM PRODUCT

WHERE PRODUCT_ID = #id#

</select>

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Simple Configuration

String resource = “SqlMapConfig.xml”;

Reader reader = Resources

.getResourceAsReader (resource);

SqlMapClient sqlMap = SqlMapClientBuilder

.buildSqlMapClient(reader);

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Executing the Query

Product product =

(Product) sqlMap.queryForObject

(“getProduct”, 5);

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…Audience: OMG! Did you just hand code SQL?

Clinton: Yes.…

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SQL

Is it still relevant?

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SQLStructured Query Language

Introduced in 1973 by IBM

Based on relational model of 1970

Based on sound mathematical principles

Significant industry investment

Has withstood the test of time

Nothing else has ever come close

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“SQL is much more than a simple data update and retrieval mechanism. SQL's query processing can perform many tasks. By hiding SQL, application developers are excluding a powerful tool.”

http://www.martinfowler.com/articles/dblogic.html

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Writing SQL is NOT a Sin!

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Is SQL what we want to avoid?

SELECT * FROM EMPLOYEE

WHERE EMPLOYEE_NUMBER = 99

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Or is it JDBC? public Employee getEmployee (int id) throws

SQLException {

Employee employee = null;

String sql = "SELECT * FROM EMPLOYEE " +

"WHERE EMPLOYEE_NUMBER = ?";

Connection conn = null;

PreparedStatement ps = null;

ResultSet rs = null;

try {

conn = dataSource.getConnection ();

ps = conn.prepareStatement(sql);

ps.setInt(1, id);

rs = ps.executeQuery();

employee = null;

while (rs.next()) {

employee = new Employee();

employee.setId (rs.getInt("EMP_ID"));

employee.setEmployeeNumber (rs.getInt("EMP_NUMBER"));

employee.setFirstName (rs.getString("EMP_FIRST_NAME"));

employee.setLastName (rs.getString("EMP_LAST_NAME"));

employee.setTitle (rs.getString("EMP_TITLE"));

}

} finally {

try {

if (rs != null) rs.close();

} finally {

try {

if (ps != null) ps.close();

} finally {

if (conn != null) conn.close();

}

}

}

return employee;

}

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iBATIS is a hybrid solution

Qualities, features and competition.

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Options…Stored procedures

Inline SQL

Dynamic SQL

Object Relational Mapping

iBATIS IS A HYBRID!

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A Hybrid?Full support for stored procedures

SQL is written just like inline SQL• “Inline SQL for XML”

Advanced dynamic SQL definition features• A big problem even for the best ORM tools

Shares many features with ORM• Caching, lazy loading, join mapping, bytecode

enhancement etc.

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Apache iBATIS…Is tolerant of complex/bad database designs

Isolates the data model

Separates concerns

Divides labor

Saves time

Reduces code

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Advanced iBATIS FeaturesSupports all types • Objects, Primitives, Arrays, Collections

Caching (use case vs. holistic)

Lazy Loading or Join Mapping (1:1, 1:M, M:N)

Bytecode enhancement (ifaces AND classes)

XML parameters and results

Transaction Management (Local/Global)

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But yes…SQL Coding is RequiredMany people consider this an advantage

Many others eventually realize it’s required

Few people consider it a problem

SQL can be done fast and done well• Use good tools (there are plenty)

• Generation is an option (but not a best practice)

• The SQL may already exist (consider app rewrites or

ports)

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Other “SQL Mapper-Like” Tools JDBC PreparedStatement

Embedded SQL as a language feature• Pro*C, Forte TOOL, SQLJ

Spring framework

Voruta

SQLC (iBATIS inspired?)

O/R Broker (iBATIS inspired)

Mr. Persister (iBATIS inspired)

Aximol SQL Library (iBATIS inspired)

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iBATIS 3 Years agoJPetStore posted on TSS

iBATIS noticed in the persistence layer

Architectural reviewer said: “Use Torque”

Why not just use ORM for everything?

What kept it going…?

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What drives open source?

Frustration / Anger / Need

Confidence / Ego

Pride

Duty

Community

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iBATIS Today~10,000 users

~1.2 Million DTD hits per month from tools

Apache Software Foundation

12 Developers

Java, .NET, Ruby

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Audience Response

Questions?

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More simple examples…To inspire questions or support answers.

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<select id="getProduct" parameterClass=“int” resultClass=“com.domain.Product">

select PRODUCT_ID as id, NAME as name, DESCN as description, CATEGORY as categoryfrom PRODUCT where PRODUCTID = #id#

</select>

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<resultMap id="productResult“

class="com.domain.Product">

<result property="id" column="PRODUCTID"/>

<result property="name" column="NAME"/>

<result property="description" column="DESCN"/>

<result property="categoryId" column="CATEGORY"/>

</resultMap>

<select id="getProduct“

parameterClass=“int”

resultMap="productResult">

select * from PRODUCT

where PRODUCTID = #id#

</select>

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<parameterMap id="productParameter“ class=“int"> <parameter property=“id"/></parameterMap>

<select id="getProduct“ parameterMap=“productParameter” resultClass=“com.domain.Product“>

select

PRODUCT_ID as id,

NAME as name,

DESCN as description,

CATEGORY as category

from PRODUCT

where PRODUCTID = ?

</select>

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<statement id=“insertProduct“

parameterClass=“com.domain.Product”>

insert into PRODUCT

values (#id#,#name#,#description#,#category#)

</statement>

<statement id=“updateProduct“

parameterClass=“com.domain.Product”>

update PRODUCT set

NAME = #name#,DESC = #description#,CATEGORY=#category#

where PRODUCT_ID = #id#

</statement>

<statement id=“deleteProduct“

parameterClass=“com.domain.Product”>

delete PRODUCT where PRODUCT_ID = #id#

</statement>

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Simple Query

Product product =(Product) sqlMap.queryForObject

(“getProduct”, 23);

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Insert, Update, DeleteProduct product = new Product();

product.setId(324);

product.setName(“Shih Tzu”);

Product.setDescription(“Some longer description.”);

product.setCategory(“DOG”);

sqlMap.insert(“insertProduct”, product);

product.setCategory(“CAT”);

sqlMap.update(“updateProduct”, product);

product.delete(“deleteProduct”, product);

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Transaction Handlingtry {

sqlMap.startTransaction();

sqlMap.insert(“insertProduct”, product);

sqlMap.update(“updateProduct”, product);

product.delete(“deleteProduct”, product);

sqlMap.commitTransaction();

} finally {

sqlMap.endTransaction();

}

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What does an application using SQL Maps look like?

See JPetStore 4