Hello-Java/src/Phase9_ModernJavaAndModules/Modules/ModuleExamples.java at master · deepakgupta7403/Hello-Java · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
packagePhase9_ModernJavaAndModules.Modules;

/**
 * Module Examples — sample `module-info.java` shapes
 * --------------------------------------------------
 * This file is a CATALOGUE of realistic module declarations. The
 * project itself is unnamed (no module-info.java), so the snippets are
 * inside comments — copy them into a modularised project to use.
 * <p>
 *
 * 1) Tiny library module
 * ----------------------
 * module com.example.utils {
 * exports com.example.utils;
 * }
 * <p>
 *
 * 2) Library + internal helpers
 * -----------------------------
 * module com.example.app {
 * requires java.net.http;
 * requires java.logging;
 * <p>
 *
 * exports com.example.app.api; // public
 * // com.example.app.internal NOT exported - module-private
 * }
 * <p>
 *
 * 3) Web app using Spring (needs reflection access)
 * -------------------------------------------------
 * module com.example.webapp {
 * requires spring.boot.autoconfigure;
 * requires spring.web;
 * requires spring.context;
 * requires java.sql;
 * <p>
 *
 * exports com.example.webapp.controller;
 * <p>
 *
 * // Spring needs reflection access to inject and proxy:
 * opens com.example.webapp.controller to spring.core;
 * opens com.example.webapp.service to spring.core;
 * opens com.example.webapp.config to spring.core;
 * }
 * <p>
 *
 * 4) Compile-time-only dependency
 * -------------------------------
 * module com.example.tooling {
 * // We use Lombok annotations at compile time only.
 * requires static lombok;
 * exports com.example.tooling;
 * }
 * <p>
 *
 * 5) Transitive dependency
 * ------------------------
 * module com.example.core {
 * requires transitive org.slf4j; // consumers see slf4j too
 * exports com.example.core;
 * }
 * <p>
 *
 * 6) Service provider
 * -------------------
 * module com.example.payments.stripe {
 * requires com.example.payments.api;
 * <p>
 *
 * provides com.example.payments.api.Gateway
 * with com.example.payments.stripe.StripeGateway;
 * }
 * <p>
 *
 * module com.example.payments.api {
 * exports com.example.payments.api;
 * uses com.example.payments.api.Gateway;
 * }
 * <p>
 *
 * 7) Open module (rarely a great idea)
 * ------------------------------------
 * open module com.legacy.app {
 * requires java.sql;
 * exports com.legacy.app.api;
 * // Every package is implicitly `opens` — full reflection.
 * }
 * <p>
 *
 * 8) Compatibility — automatic + unnamed
 * --------------------------------------
 * A plain jar with no module-info.java becomes an AUTOMATIC module if
 * placed on the --module-path. Recommended: add to your jar's MANIFEST.MF:
 * <p>
 *
 * Automatic-Module-Name: com.example.legacy
 * <p>
 *
 * so its module name is stable even before you write a real module-info.
 * <p>
 *
 * 9) Multi-release module (Java 9+)
 * ---------------------------------
 * Jars can ship per-version classes under META-INF/versions/N/. Each
 * version uses the same module-info.java (or a per-version variant).
 * <p>
 *
 * 10) `jdeps --generate-module-info`
 * ----------------------------------
 * jdeps --generate-module-info ./mods build/libs/mylib.jar
 * <p>
 *
 * Reads a jar's bytecode and produces a stub module-info.java listing
 * its real dependencies.
 */

publicclassModuleExamples {

publicstaticvoidmain(String[] args) {
section("This file is a catalogue — please open the source to read the snippets");
// Reflective examples to show that the current process is in
// the unnamed module:
Modulemine = ModuleExamples.class.getModule();
System.out.println("unnamed? = " + !mine.isNamed());
System.out.println("reads java.base? = " + mine.canRead(String.class.getModule()));
 }

privatestaticvoidsection(Stringtitle) {
System.out.println();
System.out.println("=== " + title + " ===");
 }
}