Table of Contents

1 Understanding object/relational persistence 1

What is persistence? 3

Relational databases 3 - Understanding SQL 4 - Using SQL in Java 5 - Persistence in object-oriented applications 5

The paradigm mismatch 7

The problem of granularity 9 - The problem of subtypes 10 - The problem of identity 11 - Problems relating to associations 13 - The problem of object graph navigation 14 - The cost of the mismatch 15

Persistence layers and alternatives 16

Layered architecture 17 - Hand-coding a persistence layer with SQL/JDBC 18 - Using serialization 19 - Considering EJB entity beans 20 - Object-oriented database systems 21 - Other options 22

Object/relational mapping 22

What is ORM? 23 - Generic ORM problems 25 - Why ORM? 26

Summary 29

2 Introducing and integrating Hibernate 30

"Hello World" with Hibernate 31

Understanding the architecture 36

The core interfaces 38 - Callback interfaces 40 - Types 40 - Extension interfaces 41

Basic configuration 41

Creating a SessionFactory 42 - Configuration in non-managed environments 45 - Configuration in managed environments 48

Advanced configuration settings 51

Using XML-based configuration 51 - JNDI-bound SessionFactory 53 - Logging 54 - Java Management Extensions (JMX) 55

Summary 58

3 Mapping persistent classes 59

The CaveatEmptor application 60

Analyzing the business domain 61 - The CaveatEmptor domain model 61

Implementing the domain model 64

Addressing leakage of concerns 64 - Transparent and automated persistence 65 - Writing POJOs 67 - Implementing POJO associations 69 - Adding logic to accessor methods 73

Defining the mapping metadata 75

Metadata in XML 75 - Basic property and class mappings 78 - Attribute-oriented programming 84 - Manipulating metadata at runtime 86

Understanding object identity 87

Identity versus equality 87 - Database identity with Hibernate 88 - Choosing primary keys 90

Fine-grained object models 92

Entity and value types 93 - Using components 93

Mapping class inheritance 97

Table per concrete class 97 - Table per class hierarchy 99 - Table per subclass 101 - Choosing a strategy 104

Introducing associations 105

Managed associations? 106 - Multiplicity 106 - The simplest possible association 107 - Making the association bidirectional 108 - A parent/child relationship 111

Summary 112

4 Working with persistent objects 114

The persistence lifecycle 115

Transient objects 116 - Persistent objects 117 - Detached objects 118 - The scope of object identity 119 - Outside the identity scope 121 - Implementing equals() and hashCode() 122

The persistence manager 126

Making an object persistent 126 - Updating the persistent state of a detached instance 127 - Retrieving a persistent object 129 - Updating a persistent object 129 - Making a persistent object transient 129 - Making a detached object transient 130

Using transitive persistence in Hibernate 131

Persistence by reachability 131 - Cascading persistence with Hibernate 133 - Managing auction categories 134 - Distinguishing between transient and detached instances 138

Retrieving objects 139

Retrieving objects by identifier 140 - Introducing HQL 141 - Query by criteria 142 - Query by example 143 - Fetching strategies 143 - Selecting a fetching strategy in mappings 146 - Tuning object retrieval 151

Summary 152

5 Transactions, concurrency, and caching 154

Transactions, concurrency, and caching 154

Understanding database transactions 156

JDBC and JTA transactions 157 - The Hibernate Transaction API 158 - Flushing the Session 160 - Understanding isolation levels 161 - Choosing an isolation level 163 - Setting an isolation level 165 - Using pessimistic locking 165

Working with application transactions 168

Using managed versioning 169 - Granularity of a Session 172 - Other ways to implement optimistic locking 174

Caching theory and practice 175

Caching strategies and scopes 176 - The Hibernate cache architecture 179 - Caching in practice 185

Summary 194

6 Advanced mapping concepts 195

Understanding the Hibernate type system 196

Built-in mapping types 198 - Using mapping types 200

Mapping collections of value types 211

Sets, bags, lists, and maps 211

Mapping entity associations 220

One-to-one associations 220 - Many-to-many associations 225

Mapping polymorphic associations 234

Polymorphic many-to-one associations 234 - Polymorphic collections 236 - Polymorphic associations and table-per- concrete-class 237

Summary 239

7 Retrieving objects efficiently 241

Executing queries 243

The query interfaces 243 - Binding parameters 245 - Using named queries 249

Basic queries for objects 250

The simplest query 250 - Using aliases 251 - Polymorphic queries 251 - Restriction 252 - Comparison operators 253 - String matching 255 - Logical operators 256 - Ordering query results 257

Joining associations 258

Hibernate join options 259 - Fetching associations 260 - Using aliases with joins 262 - Using implicit joins 265 - Theta-style joins 267 - Comparing identifiers 268

Writing report queries 269

Projection 270 - Using aggregation 272 - Grouping 273

Restricting groups with having 274 - Improving performance with report queries 275

Advanced query techniques 276

Dynamic queries 276 - Collection filters 279 - Subqueries 281 - Native SQL queries 283

Optimizing object retrieval 286

Solving the n+1 selects problem 286 - Using iterate() queries 289 - Caching queries 290

Summary 292

8 Writing Hibernate applications 294

Designing layered applications 295

Using Hibernate in a servlet engine 296 - Using Hibernate in an EJB container 311

Implementing application transactions 320

Approving a new auction 321 - Doing it the hard way 322 - Using detached persistent objects 324 - Using a long session 325 - Choosing an approach to application transactions 329

Handling special kinds of data 330

Legacy schemas and composite keys 330 - Audit logging 340

Summary 347

9 Using the toolset 348

Development processes 349

Top down 350 - Bottom up 350 - Middle out (metadata oriented) 350 - Meet in the middle 350 - Roundtripping 351

Automatic schema generation 351

Preparing the mapping metadata 352 - Creating the schema 355 - Updating the schema 357

Generating POJO code 358

Adding meta-attributes 358 - Generating finders 360 - Configuring hbm2java 362 - Running hbm2java 363

Existing schemas and Middlegen 364

Starting Middlegen 364 - Restricting tables and relationships 366 - Customizing the metadata generation 368 - Generating hbm2java and XDoclet metadata 370

XDoclet 372

Setting value type attributes 372 - Mapping entity associations 374 - Running XDoclet 375

Summary 376

appendix A: SQL fundamentals 378

appendix B: ORM implementation strategies 382

Properties or fields? 383

Dirty-checking strategies 384

appendix C: Back in the real world 388

The strange copy 389

The more the better 390

We don?t need primary keys 390

Time isn?t linear 391

Dynamically unsafe 391

To synchronize or not? 392

Really fat client 393

Resuming Hibernate 394

 
references 395
index 397